Prof. Janardhan Padmanabhan, FNA
- Curriculum Vitae  -
[For Updated Version - link is at the Top Right Hand Corner]

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(5) Membership of Academic Bodies:

1. Individual Member URSI (MURSI)


2. Member National Committee of COSPAR-URSI-SCOSTEP


3. Member Union Radio-Scientifique Internationale (URSI)


4. Member of the International Astronomical Union (IAU).


5. Member of the American Geophysical Union (AGU).

(6)  Awards and Honours:

1. The Chandrayaan-2 CLASS payload and the XSM payload teams were awarded the ASI Zubin-Kembhavi Award in 2024 for Observational and Instrumentation work in Astronomy. The award, given annually, has been instituted by the Astronomical Society of India (ASI) and carries a cash prize of one lakh rupees and a plaque.


2. Elected Fellow of the Indian National Science Academy (INSA), 2019


3. Awarded the - ISRO Merit Award - 2015.  The award is conferred for outstanding performance and high productivity.  The award comprising a medal, a citation and a cash prize of Rs. 1 lakh is given annually.


4. Awarded the - Vikram Sarabhai Research Award in Space Sciences for the year 2003. The award comprising of a medal plus a cash prize of Rupees Fifty Thousand is given bi-annually.


5. Awarded the Alexander Von Humboldt Research Fellowship in Astrophysics for the year 1996 by the Alexander Von Humboldt Foundation, Bonn, Germany.


6. Was selected as a "Young Astronomer" in 1988 for the award of a National Science Foundation (NSF, U.S.A.) Grant to attend the Twentieth General Assembly of the International Astronomical Union.

(7) Additional information:

1. From 2008 to 2020 I was the Principal Investigator (PI) of the Aditya Solarwind Particle Experiment [ASPEX] Payload onboard India’s first dedicated solar mission (ADITYA-L1) to the L1 Lagrangian point of the Sun-Earth system, which is due for launch in 2022.

2. An article on our work was featured in Times of India entitled “ Sunspots point to Looming Little Ice Age. Times of India - April 2016

3. An Article Entitled - A New Angle on the Effects of Solar Wind on a novel method of detecting geoeffective CIR was published online on 07 Sept. 2017 in Nature India 2017 doi:10.1038/nindia.2017.116

4. Recent Work on Ducting Emission observed far away from a flaring site was Reported as a CESRA (Community of European Solar Radio Astronomers) Science Nugget −− Solar Radio Science Highlight - 04 Sept. 2018.

5. An article entitled - Sun’s reversed polarity field may affect Earth’s climate was published online in Nature India - 26 Nov. 2018. doi:10.1038/nindia.2018.153

6. An article on our work was featured in Times of India entitled “ The Suns Magnetic field is weakening" Times of India - October 2019

7. Our Work on Astrochemical Ices and the Synthesis of N-Graphene was reported online in an article entitled Pencil Lead in Space −15 Sept. 2020.

8. Our Work on a new method for predicting the amplitude of an on coming solar cycle was reported in the journal Current Science as a News Report−25July2020. The link to the published work can be found here.

9. My work on Weakening Solar Magnetic Fields and the possibility of the onset of a Maunder Type Solar Minimum was summarized in a short online article in The Wire - 04 Nov. 2020.

(8)  List of Refereed Journal Publications

           1989 - 1990:

1. Quasar Enhanced.
   Alurkar, S.K., Sharma, A.K., Janardhan, P ., and Bhonsle, R.V. (1989). Nature, 338, 211−212.
   
   
2. Three-Site Solar Wind Observatory.
   Alurkar, S.K.,Bobra, A.D., Nirman, N.S., Venat, P., and Janardhan, P. (1989). Ind. Jou. Pure and Appl. Phys., 27, 322−330.
   
   
3. Interplanetary Scintillation Network for 3-Dimensional Space Exploration in India.
   Bhonsle, R.V., Alurkar, S.K., Bobra, A.D., Lali, K.S., Nirman, N.S., Venat, P., Sharma, A.K. and Janardhan, P. (1990). Acta Astronautica, 21, No. 3, 189−196.
   
   1991 - 1995:
   
   
4. Estimation of electron density in the ion-tail of comet Halley using 103 MHz IPS observations.
   Sharma, A. K., Alurkar, S. K. and Janardhan, P. (1991). Bull. Astr. Soc. India, 19, 82.
   
   
5. Enhanced scintillation of radio source 2204+29 by comet Austin (1989c1) at 103 MHz.
   Janardhan, P., Alurkar, S. K., Bobra, A. D., Slee, O. B. (1991). Bull. Astr. Soc. India, 19, 204.
   
   
6. Enhanced Radio Source Scintillation Due to Comet Austin(1989 c1).
   Janardhan, P., Alurkar, S.K.,Bobra, A.D. and Slee, O.B. (1991). Aus. Jou. Phys., 44, 565−571.
   
   
7. Power Spectral Analysis of Enhanced Scintillation of Quasar 3C459 Due to Comet Halley.
   Janardhan, P., Alurkar, S.K.,Bobra, A.D., Slee, O.B. and Waldron, D. (1992). Aust. J. of Phys., 45, No. 1, 115.
   
   
8. Possible Contribution of a Solar Transient to Enhanced Scintillation Due to a Quasar.
   Janardhan, P. and Alurkar, S.K. (1992). Earth, Moon, and Planets, 58, 31−38.
   
   
9. Comparison of Single-Site Interplanetary Scintillation Solar Wind Speed Structure With Coronal Features.
   Alurkar, S.K., Janardhan, P. and Vats, H.O. (1993). Sol. Phys., 144, No.2, 385−397.
   
   
10. Angular Source Size Measurements and Interstellar Scattering at 103 MHz Using Interplanetary Scintillation.
    Janardhan, P. and Alurkar, S.K. (1993). Astronomy & Astrophys ., 269, 119−127.
    
    
11. Measurements of Compact Radio Source Size and Structure of Cometary Ion Tails Using Interplanetary Scintillation at 103 MHz.
    Janardhan, P. (1993). Bull. Astr. Soc. India, 21, 381.
    
    
12. IPS Survey at 327 MHz for Detection of Compact Radio Sources.
    Balasubramanian, V., Janardhan, P ., Ananthakrishnan, S., and Manoharan, P.K. (1993). Bull. Astr. Soc. India, 21, 469−471.
    
    
13. Observations of PSR 0950+08 at 103 MHz.
    Deshpande, M.R., Vats, H.O., Janardhan, P ., and Bobra, A.D. (1993). Bull. Astr. Soc. India, 21, 613−614.
    
    
14. Terrestrial Effects of PSR 0950+08.
    Vats, H.O., Deshpande, M.R., Janardhan, P ., Harish, C., and Vyas, G.D. (1993). Bull. Astr. Soc. India , 21, 615−617.
    
    
15. Radio and X-ray burst from PSR 0950+08.
    Deshpande, M.R., Vats, H.O., Chandra Harish, Janardhan, P., Bobra, A.D. and, Vyas, G.D. (1994). Astrophys. Space Sci., 218, No.2, 249−265.
    
    
16. Latitudinal Variation of Solar Wind Velocity.
    Ananthakrishnan, S., Balasubramanian, V., and Janardhan, P. (1995). Space Sci. Rev ., 72, 229−232.
    
    
17. A 327-MHZ Interplanetary Scintillation Survey Of Radio Sources Over 6-Steradian.
    Balasubramanian, V., Janardhan, P . and Ananthakrishnan, S. (1995). Jou. Astrophys. & Astron., 16, 298.
    
    
18. Unique Observations of PSR 0950+08 and Possible Terrestrial Effects.
    M.R. Deshpande, H.O. Vats, P. Janardhan, A.D. Bobra, Harish Chandra, and G.D.Vyas. (1995). Jou. Astrophys. & Astron ., 16, 253.
    
    1996 - 2000:
    
    
19. On the Nature of Compact Components of Radio Sources at 327 MHz.
    Balasubramanian, V., Janardhan, P., Ananthakrishnan, S. and Srivatsan, R. (1996). Bull. Astr. Soc. India, 24, 829.
    
    
20. IPS Observations of the Solar Wind at 327 MHz - A Comparison with Ulysses Observations.
    Janardhan, P ., Balasubramanian, V., Ananthakrishnan, S. and Srivatsan, R. (1996). Bull. Astr. Soc. India , 24, 645.
    
    
21. Travelling Interplanetary Disturbances Detected Using Interplanetary Scintillation at 327 MHz.
    Janardhan, P., Balasubramanian, V., Ananthakrishnan, S., Dryer, M., Bhatnagar, A. and McIntosh, P.S. (1996). Sol. Phys., 166, 379−401.
    
    
22. Radio Detection of Ammonia in Comet Hale−Bopp.
    Bird, M. K., Huchtmeier, W., Gensheimer, P., Wilson, T. L., Janardhan, P. and Lemme, C. (1997). A&A Lett., 325, L5−L8.
    
    
23. Ammonia in Comet Hale-Bopp.
    Wilson, T. L., Huchtmeier, W. K., Bird, M. K., Janardhan, P., Gensheimer, P. and Lemme, C., (1997). Bulletin of the American Astronomical Soc., 29, 1259.
    
    
24. Detection and Tracking of IPS Disturbances Using Interplanetary Scintillation.
    Balasubramanian, V., Srivatsan, R., Janardhan, P., and Ananthakrishnan, S. (1998). Bull. Astr. Soc. India, 26, 225−229.
    
    
25. Coronal Velocity Measurements with Ulysses: Multi−link Correlation Studies During two Superior Conjunctions.
    Janardhan, P., Bird, M K., Edenhofer, P, Plettemeier, D., Wohlmuth, R., Asmar, S W., Patzölt, M. and Karl, J. (1999). Sol. Phys., 184, 157−172.
    
    
26. K−Band Detection of Ammonia and (Possibly) Water in Comet Hale−Bopp.
    Bird, M. K., Janardhan, P., Wilson, T. L., Huchtmeier, W., Gensheimer, P., and Lemme, C. (1997). Earth Moon and Planets, 78, 21−28.
    
    
27. Anisotropic Structure of the Solar Wind in its Region of Acceleration.
    Efimov, A.I., Rudash, V.K., Bird, M.K., Janardhan, P., Patzölt, M., Karl, J., Edenhofer, P. and Wohlmuth, R. (2000). Advances in Space Res., 26, 785−788.
    
    
28. Radio Detection of a Rapid Disturbance Launched by a Solar Flare.
    White, S.M., Janardhan, P. and Kundu, M.R. (2000). ApJ Lett., 533 , L167−L170.
    
    
29. Observations of Interplanetary Scintillation During the 1998 Whole Sun Month: A Comparison between EISCAT, ORT and Nagoya Data.
    Moran, P.J., Breen, A.R., Canals, A., Markkanen, J., Janardhan, P., Tokumaru, M. and Williams, P.J.S. (2000). Annales Geophysica, 18, 1003.
    
    
30. H−alpha Observations of Be Stars.
    Banerjee, D.P.K., Rawat, S.D. and Janardhan, P. (2000). A&A Suppl., 147, 229.
    
    2001 − 2005:
    
    
31. Near Infra−red and Optical Spectroscopy of Delta Scorpii.
    Banerjee, D.P.K., Janardhan, P. and Ashok, N.M. (2001). A&A Lett., 380, L13.
    
    
32. Flow Sources and Formation Laws of Solar Wind Streams.
    Lotova, N.A., Obridko, V.N., Vladimirskii, K.V., Bird, M.K. and Janardhan, P. (2002). Sol. Phys., 205, 149.
    
    
33. Fine Structure of the Solar Wind Turbulence Inferred from Simultaneous Radio Occultation Observations at Widely−Spaced Ground Stations.
    Bird, M.K., Janardhan, P ., Efimov, A.I., Samoznaev, L.N., Andreev, V.E., Chashei, I.V., Edenhofer, P., Plettemeier, D., and Wohlmuth, R. (2003). Solar Wind 10, AIP Conf. Proc. 679, 465−468. AIP Press, Melville, New York, USA. Eds.  M. Velli et al.
    
    
34. IPS Observations of the Solar Wind Disappearance Event of May 1999.
    Balasubramanian, V., Janardhan, P., Srinivasan, S., and Ananthakrishnan, S. (2003). Jou. Geophys. Res. 108, A3, 1121.
    
    
35. Giant Meter Wave Radio telescope Observations of an M2.8 Flare: Insights into the Initiation of a Flare−Coronal Mass Ejection Event.
    Prasad Subramanian, Ananthakrishnan, S., Janardhan, P. , Kundu, M.R., White, S.M., Garaimov, V.I. (2003). Sol. Phys. 218, 247−259.
    
    
36. The Solar Wind and Interplanetary Disturbances.
    Janardhan, P., (2003). Solar Terrestrial Environment  − Space Weather, Allied Publishers, New Delhi., pp. 42−56.
    Eds.     R.P.Singh, Rajesh Singh & Ashok Kumar, Banaras Hindu University, Varanasi, India. ISBN:  81−7764−494−7.
    
    
37. Radio Observations of Rapid Acceleration in a Slow Filament Eruption/Fast CME Event.
    Kundu, M.R., Garaimov, V.I., White, S.M., Manoharan, P.K., Subramanian, S., Ananthakrishnan, S., and Janardhan, P. (2004). Ap J. 607, 530−539.
    
    
38. Resolving the Enigmatic Solar Wind Disappearance Event of 11 May 1999.
    Janardhan, P. , Fujiki, K., Kojima, M., Tokumaru, M., and Hakamada, K. (2005). Jou. Geophys. Res.110, A08101.
    
    2006 − 2010:
    
    
39. Combining visibilities from the Giant Meterwave Radio Telescope and the Nancay Radio Heliograph.
    Mercier, C., Prasad Subramanian, Kerdraon, A., Pick, M., Ananthakrishnan, S. and Janardhan, P. (2006). A&A. 447, 1189−1201.
    
    
40. The Morphology of Decimetric Emission from Solar Flares: GMRT Observations.
    Kundu, M.R., White, S.M., Garaimov, V.I., Subramanian, S., Ananthakrishnan, S., and Janardhan, P. (2006). Sol. Phys. 236, 369−387.
    
    
41. Enigmatic solar wind disappearance events: Do we understand them?.
    Janardhan, P., (2006). Jou. Astrophys. Astron. 27, 1−7.
    
    
42. Locating the solar source of the extremely low−density, low−velocity solar wind flows of 11 May 1999.
    Janardhan, P., Fujiki, K., Kojima, M. and Tokumaru, M. (2007). Proc. of the ILWS Workshop 2006, p.132−138.
    Eds.    N. Gopalswamy and A. Bhattacharya
    ISBN:  81−87099−40−2
    
    
43. Insights gained from Ground and Space Based Studies of Long Lasting Low Density Anomalies at 1 AU.
    Janardhan, P. , Ananthakrishnan, S., Balasubramanian, V., (2007). Asian Jou. Phys., 16, 209−232.
    Eds.   Janardhan, P., Vats, H.O., Iyer, K.N., & Anandarao, B.G.
    
    
44. Prospects for GMRT to Observe Radio Waves from UHE Particles Interacting with the Moon.
    Sukanta P., Mohanty, S., Janardhan, P. , and Oscar, S., (2007). JCAP., 11, 022−038.
    
    
45. The Source Regions of Solar Wind Disappearance Events.
    Janardhan, P. , Fujiki, K., Sawant, H.S., Kojima, M., Hakamada, K. and Krishnan, R., (2008). Jou. Geophys. Res. 113, A03102.
    
    
46. The Solar Wind Disappearance Event of 11 May 1999: Source Region Evolution.
    Janardhan, P. , Tripathi, D., and Mason, H. (2008). A&A Lett.  488, L1−L4.
    
    
47. Solar Polar Fields During Cycles 21 - 23: Correlation with Meridional Flows.
    Janardhan, P., Susanta Kumar Bisoi and Gosain, S., (2010).  Sol. Phys. 267, 267−277.
    
    
48. Unique Observations of Geomagnetic SI⁺ - SI^- pair and Solar Wind Fluctuations.
    Rastogi, R.G., Janardhan, P., Ahmed, K., Das, A.C. and Susanta Kumar Bisoi (2010).  Jou. Geophys. Res. 115, A12110, doi:10.1029/2010JA015708.
    
    2011 − 2015:
    
    
49. The Prelude to the Deep Minimum between Solar Cycles 23 and 24: Interplanetary Scintillation Signatures in the Inner Heliosphere
    Janardhan, P., Susanta Kumar Bisoi, Ananthakrishnan, S., Tokumaru, M., Fujiki, K., (2011).  Geophys. Res. Lett., 38,  L20108, doi:10.1029/2011GL049227.
    
    
50. Deep GMRT 150 MHz observations of the DEEP2 fields: Searching for High Red-shift Radio Galaxies Revisited
    Susanta Kumar Bisoi., Ishwara-Chandra, C.H., Sirothia, S.K., and Janardhan, P. (2011).  Jou. Astrophys. Astr. 32, 613−614.  DOI: 10.1007/s12036-011-9116-2.
    
    
51. Near-Infrared Monitoring and Modelling of V1647 Ori in its On-going 2008-12 Outburst Phase
    Venkata Raman, V., Anandarao, B.G., Janardhan, P. and Pandey, R.  (2013).  Res. Astron. Astrophys. 13, No. 9, 1107−1117. 
    
    
52. Changes in quasi-periodic variations of solar photospheric fields: precursor to the deep solar minimum in the cycle 23?
    Susanta Kumar Bisoi, Janardhan,P., Chakrabarty, D., Ananthakrishnan, S. and Divekar,A. (2014).  Sol. Phys.  289, 41−61.  DOI:  10.1007/s11207-013-0335-3.
    
    
53. Spread-F during the magnetic storm of 22 January 2004 at low latitudes: Effect of IMF-Bz in relation to local sunset time
    Rastogi,R.G., Chandra, H., Janardhan,P., Thai Lan Hoang, Louis Condori, Pant, T.K., Prasad, D.S.V.V.D. and Reinish, B.W. (2014).   Jou. Earth System Sci.  123, 1273−1285. 
    
    
54. Determination of mass and orbital parameters of a low-mass star HD 213597B
    Priyanka Chaturvedi1, Rohit Deshpande, Vaibhav Dixit, Arpita Roy Abhijit Chakraborty, Suvrath Mahadevan, B.G. Anandarao, Leslie Hebb and P. Janardhan (2014). 
    MNRAS  442,3737−3744, DOI: 10.1093/mnras/stul127.
    
    
55. A study of density modulation index in the inner solar wind during solar cycle 23
    Susanta Kumar Bisoi, P. Janardhan, M. Ingale and P. Subramanian, and S. Ananthakrishnan  (2014).  Atrophysical Journal  795, 69−76.
    
    
56. Equatorial and mid-latitude ionospheric currents over the Indian region based on 40 years of data at Trivandrum and Alibag
    Rastogi,R.G., Chandra, H., Janardhan, P., and Rahul Shah  (2014).  IJRSP  43, 274−283.
    
    
57. The Structure of Solar Radio Noise Storms
    C. Mercier, Prasad Subramanian, G. Chambe, Janardhan, P., (2015).  A&A. 576, A136
    
    
58. A Twenty Year Decline in Solar Photospheric Magnetic Fields: Inner-Heliospheric Signatures and Possible Implications?
    P. Janardhan, Susanta Kumar Bisoi, S. Ananthakrishnan, Tokumaru, M., and Fujiki, K., Jose, L., and Sridharan, R.  (2015).  Jou. Geophys. Res. 120, 5306--5317, doi:10.1002/2015JA021123.
    
    
59. Solar and Interplanetary Signatures of a Maunder-like Grand Solar Minimum around the Corner - Implications to Near-Earth Space
    P. Janardhan, Susanta Kumar Bisoi, S. Ananthakrishnan, R. Sridharan and L. Jose  (2015).  Sun and Geosphere  10, No. 2, 147--156.
    
    2016 − 2020:
    
    
60. A Prolonged Southward IMF-Bz Event of May 02 -- 04, 1998: Solar, Interplanetary Causes and Geomagnetic Consequences
    Susanta Kumar Bisoi, Chakrabarty,D., Janardhan, P., Rastogi, R.G., Yoshikawa, A., Fujiki, K., Tokumaru, M., and Yan, Y. (2016). Jou. Geophys. Res. 121, 3882 -- 3904, doi:10.1002/2015JA022185.
    
    
61. J1216+0709 : A Radio Galaxy with Three Episodes of AGN Jet Activity
    Veeresh Singh, Ishwara-Chandra, C.H., Preeti Kharb, Shweta Srivastava Janardhan, P., (2016). ApJ   826, 132--137, doi:10.3847/0004-637X/826/2/132.
    
    
62. Star formation activity in the neighbourhood of WR 1503-160L star in the mid-infrared bubble N46
    Dewangan, L.K., Baug, T., Ojha, D.K.,Janardhan,P. Ninan, J. P., Luna, A. and Zinchenko, I. (2016). ApJ   826, 27--55, doi: 10.3847/0004-637X/826/1/27.
    
    
63. Amplitude of solar wind density turbulence from 10 R_s - 45 R_s
    K. Sasikumar Raja, Madhusudan Ingale, R. Ramesh, Prasad Subramanian, P. K., Manoharan and P. Janardhan. (2016). Jou. Geophys. Res 121, A10, doi: 10.1002/2016JA023254.
    
    
64. A 20 year decline in solar magnetic fields and solar wind micro-turbulence levels: Are we heading towards a Maunder-like minimum?
    Janardhan, P., Bisoi, S. K., and Ananthakrishnan, S. (2016). Proc. URSI-APRASC-2016 pp: 1079--1082.
    
    
65. The physical environment around IRAS 17599-2148: Infrared dark cloud and bipolar nebula
    Dewangan, L.K., Ojha, D.K., Zinchenko, Janardhan, P., Ghosh, S.K. and Luna, A. (2016). ApJ   833, doi: 10.3847/1538-4357/833/2/246.
    
    
66. Multi-wavelength study of the star-formation in the S237 HII Region
    Dewangan, L.K., Ojha, D.K., Zinchenko, Janardhan,P. and Luna, A. (2017). ApJ 834, doi: 10.3847/1538-4357/834/1/22.
    
    
67. Solar wind flow angle and geo-effectiveness of corotating interaction regions: First results
    Diptiranjan Rout, Chakrabarty, D., Janardhan, P., Sekar, R., Vrunda Maniya and Kuldeep Pandey (2017).  Geophys. Res. Lett. 44, 4532-4539  doi: 10.1002/2017GL073038.
    
    
68. Probing the heliosphere using in-situ payloads on-board Aditya-L1
    Janardhan, P., Santosh Vadawale, Bhas Bapat, Subramanian, K. P., Chakrabarty D., Prashant Kumar, Aveek Sarkar, Nandita Srivastava, Satheesh Thampi R., Vipin K. Yadav,
    Dhanya M. B., Govind G. Nampoothiri, Abhishek J. K., Anil Bhardwaj and Subhalakshmi K. (2017).  Current Science 113,  No. 4, 620-624, doi: 10.18520/cs/v113/i04/620-624 .
    
    
69. An Infrared Photometric and Spectroscopic Study of Post-AGB Stars
    Venkata Raman, V., Anandarao, B. G., Janardhan, P., and Pandey, R. (2017).  MNRAS 470, 1593-1611.  DOI:doi:10.1093/mnras/stx1237.
    
    
70. Post sunset equatorial spread-F at Kwajalein and interplanetary magnetic field
    Rastogi, R.G., Chandra, H., Janardhan, P., Reinisch, B.W. and Susanta Kumar Bisoi (2017).  Jou. Adv. Space Res. 60, 1708-1715.
    
    
71. The molecular cloud S242: Physical environment and star formation activities
    Dewangan, L.K., Baug, T., Ojha, D.K., Janardhan, P., Devraj, R., and Luna, A., (2017).  ApJ  845, 34-47.
    
    
72. Effect of Solar Flare on the Equatorial Electrojet in the Eastern Brazil Region
    Rastogi, R.G., Janardhan, P., Chandra, H., Trivedi, N.B., and Vidal Erick, (2017).  JESS 126, 51. DOI:10.1007/s12040-017-0837-8 .
    
    
73. Aditya Solarwind Particle EXperiment (ASPEX) onboard the Aditya-L1 Mission
    S. K. Goyal, P. Kumar Janardhan, P., S. V. Vadawale, A. Sarkar, M. Shanmugam, K. P. Subramanian, B. Bapat, D. Chakrabarty,P. R. Adhyaru, A. R. Patel, S. B. Banerjee,
    Manan S. Shah, Neeraj K. Tiwari, H. L. Adalja, T. Ladiya, M. B. Dadhania, A. Sarda, A. K. Hait, M. Chauhan and R. R. Bhavsar (2018).  Planetary Space Sci.  163,42-55.
    
    
74. Decimetric emission 500^" away from a flaring site: possible scenarios from GMRT solar radio observations
    Susanta Kumar Bisoi., Sawant, H.S., Janardhan, P., Yan, Y., Chen, L., Arun Kumar Awasthi., Shweta Srivastava and Gao, G. (2018). ApJ    862, 65-79.
    
    
75. Solar Polar Fields During Cycle 24: An Unusual Polar Field Reversal
    Janardhan, P., Fujiki, K., Ingale, M., Susanta Kumar Bisoi and Diptiranjan Rout (2018). A&A   618, A148.
    
    
76. Beyond the mini-solar maximum of solar cycle 24: Declining solar magnetic fields and the response of the terrestrial magnetosphere
    Ingale, M., Janardhan, P., and Susanta Kumar Bisoi. (2019). JGR, 124, https://doi.org/10.1029/2019JA026616
    
    
77. Global solar magnetic field and interplanetary scintillations during the past four solar cycles
    Sasikumar Raja., Janardhan, P., Susanta Kumar Bisoi, Ingale, M., Prasad Subramanian, Fujiki, K., and Maksimovic, M. (2019). Sol. Phys., 294, 123-136, DOI: 10.1007/s11207-019-1514-7
    
    
78. Infrared attenuation due to phase change from amorphous to crystalline observed in astrochemical propargyl ether ices.
    Rahul, K.K., Meka,J.K., Pavithraa,S., Gorai, P., Das, A., Lo, J.-I., Rajasekhar, B.N., Cheng, B.-M., Janardhan, P., Bhardwaj, A., Mason, N.J., and Sivaraman, B. (2020). Spectrochemica Acta,224, DOI: 10.1016/j.saa.2019.117393
    
    
79. Residue from vacuum ultraviolet irradiation of benzene ices: Insights into the physical structure of astrophysical dust
    Rahul, K.K., Shiva, K., Meka,J.K., Das, A., Vijayanand, C., Rajasekhar, B.N., Lo, J.-I., Cheng, B.-M., Janardhan, P., Bhardwaj, A., Mason, N.J., and Sivaraman, B. (2020). Spectrochemica Acta,   DOI:10.1016/j.saa.2019.117797.   Also appeared on the cover page of ASTROPAH Newsletter AstroPAH #65 downloadable here “Picture of the Month”
    
    
80. Another Mini Solar Maximum in the Offing: A Prediction for the Amplitude of Solar Cycle 25
    Susanta Kumar Bisoi., Janardhan, P. and Ananthakrishnan, S. (2019). JGR,  125,  DOI:2019JA027508.
    
    
81. A New Tool for Predicting the Solar Cycle: Correlation between Flux Transport at the Equator and the Poles
    Susanta Kumar Bisoi., and Janardhan, P., (2020). Sol. Phys.  DOI:10.1007/s11207-020-01645-9
    
    
82. Solar X-Ray Monitor on Board the Chandrayaan-2 Orbiter: In-Flight Performance and Science Prospects
    N.P.S. Mithun, Santosh V, Aveek Sarkar, M. Shanmugam, Arpit R. Patel, Biswajit Mondal, Bhuwan Joshi, P. Janardhan , Hiteshkumar L. Adalja,Shiv Kumar Goyal, Tinkal Ladiya, Neeraj Kumar Tiwari, Nishant Singh, Sushil Kumar, Manoj K. Tiwari, M.H. Modi, Anil Bhardwaj. (2020), Sol. Phys., 295, Issue 10, DOI:10.1007/s11207-020-01712-1
    
    2021 − Present:
    
    
83. Ground Calibration of Solar X-ray Monitor On Board the Chandrayaan-2 Orbiter
    N. P. S. Mithun, Santosh V. Vadawale, M. Shanmugam , Arpit R. Patel, Neeraj Kumar, Tiwari, Hiteshkumar L. Adalja, Shiv Kumar Goyal, Tinkal Ladiya, Nishant Singh, Sushil, Kumar, Manoj K. Tiwari, M. H. Modi, Biswajit Mondal, Aveek Sarkar, Bhuwan Joshi, P. Janardhan, Anil Bhardwaj. (2021). Expt. Astronomy 51, 33-60, DOI:10.1007/s10686-020-09686-5.
    
    
84. Observations of the Quiet Sun During the Deepest Solar Minimum of the Past Century with Chandrayaan-2 XSM - Elemental Abundances in the Quiescent Corona
    Santosh V., Biswajit Mondal, N. P. S. Mithun, Aveek Sarkar, Janardhan, P., Bhuwan Joshi , Anil Bhardwaj, M. Shanmugam, Arpit R. Patel, Hitesh Kumar L. Adalja, Shiv Kumar Goyal , Tinkal Ladiya, Neeraj Kumar Tiwari, Nishant Singh, and Sushil Kumar. (2021).   ApJ. Lett., 912., L12, DOI: 10.3847/2041-8213/abf35d.
    
    
85. Observations of the Quiet Sun During the Deepest Solar Minimum of the Past Century with Chandrayaan-2 XSM - Sub-A Class Microflares Outside Active Regions
    Santosh V., N. P. S. Mithun, Biswajit Mondal, Aveek Sarkar, Janardhan, P., Bhuwan Joshi, Anil Bhardwaj, M. Shanmugam, Arpit R. Patel, Hitesh Kumar L. Adalja, Shiv Kumar Goyal, Tinkal Ladiya, Neeraj Kumar Tiwari, Nishant Singh, and Sushil Kumar. (2021). ApJ. Lett., 912, L13, DOI: 10.3847/2041-8213/abf0b0.
    
    
86. Evolution of Elemental Abundances During B-Class Solar Flares: Soft X-ray Spectral Measurements with Chandrayaan-2 XSM
    Biswajit Mondal, Aveek Sarkar, Santosh V. Vadawale, N. P. S. Mithun, Janardhan, P ., Giulio Del Zanna, Helen E. Mason, Urmila Mitra-Kraev, and Shyama Narendranath K C (2021). ApJ., 920, 4, DOI:10.3847/1538-4357/ac14c1
    
    
87. Multiwavelength Observations by XSM, Hinode, and SDO of an Active Region. Chemical Abundances and Temperatures
    G. Del Zanna, B. Mondal, Y. K. Rao, N. P. S. Mithun, S. V. Vadawale, K. K. Reeves, H. E. Mason, A. Sarkar, P. Janardhan , and A. Bhardwaj. (2022). ApJ, 934, 159, DOI:10.3847/1538-4357/ac7a9a
    
    
88. Shock Induced Transformation of Non-Magnetic to Magnetic ISM Dust Analogue
    Arijit Roy, V. S. Surendra, J. K. Meka, R. Ramachandran, D. Sahu, A. Goutam, T. Vijay, V. Jayaram, P. Janardhan , B. N. Rajasekhar, Anil Bhardwaj, N. J. Mason, and B. Sivaraman. (2023). MNRAS, 517, 4845 – 4855, DOI:10.1093/mnras/stac2637
    
    
89. Evolution of Elemental Abundances during B-Class Solar Flares: Soft X-Ray Spectral Measurements with Chandrayaan-2 XSM
    Biswajit Mondal, Aveek Sarkar, Santosh V. Vadawale , N. P. S. Mithun, P. Janardhan , Giulio Del Zanna, Helen E. Mason, Urmila Mitra-Kraev, and S. Narendranath. (2021). ApJ , 920, 4, DOI:10.3847/1538-4357/ac14c1
    
    
90. Shock Processing of Amorphous Carbon Nanodust
    Arijit Roy, V.S. Surendra, M. Ambresh, D. Sahu, J.K. Meka, R. Ramachandran, P. Samarth, S. Pavithraa, V. Jayaram, H. Hill, J. Cami, B.N. Rajasekhar, P. Janardhan , Anil Bhardwaj, N.J. Mason, B. Sivaraman. (2022). JASR, 16047, DOI:10.1016/j.asr.2022.06.068
    
    
91. Soft X-ray Spectral Diagnostics of Multi-thermal Plasma in Solar Flares with Chandrayaan-2 XSM
    N. P. S. Mithun, Santosh V. Vadawale, Giulio Del Zanna, Yamini K. Rao, Bhuwan Joshi, Aveek Sarkar, Biswajit Mondal, P. Janardhan , Anil Bhardwaj, and Helen E. Mason. (2022). ApJ ., 939, 112, DOI:10.3847/1538-4357/ac98b4
    
    
92. N-Graphene Synthesized in Astrochemical Ices
    Rahul K K, Ambresh M, Sahu D, Meka J K, Chou S-L, Wu Y-J, Gupta D, Das A, Lo J-I, Cheng B-M, Raja Sekhar B N, Bhardwaj A, Hill H, Janardhan P , Mason N J, Sivaraman B. (2023). European Physical Journal--D.,   [In Press]
    
    
93. The Origin of Extremely Non-radial Solarwind Outflows
    Diptiranjan Rout, Janardhan P ., Fujiki, K., Chakrabarty, D., and Bisoi, S. K. (2023). ApJ, [Under Revision – Post Referee Inputs].
    
    
94. Mid-IR Characterization of 1 and 2 Cyanonaphthalene Under Conditions Commensurate with Cold Dust in the Interstellar Medium
    K K Rahul, J K Meka, A Roy, S Pavithraa, A Das, B N Raja Sekhar, Janardhan, P ., Anil Bhardwaj, N J Mason, B Sivaraman (2023). Solid State Communications., [Under Review]
    
    Papers Published in Referred Proceedings:
    
    
95. Simultaneous Observations of Large Enhancement In the Flux of PSR 0950+08 Over a 200 KM Baseline at 103 MHz.
    Bobra, A. D., Chandra, H., Vats, H. O.,  Janardhan, P.,  Vyas, G. D., Deshpande, M. R., (1996).  Proc. of the 160^th IAU Colloquium− ASP Conf. Series .,  pp. 477−448.  Eds.   S. Johnston, M.A. Walker, and M. Bailes. 
    
    
96. Tracking Interplanetary Disturbances Using Interplanetary Scintillation.
    Janardhan, P., Balasubramanian, V. and Ananthakrishnan, S. (1997).  Proc. 31st. ESLAB Symp., ESA SP−415 , pp. 177−181. 
    
    
97. Study of Solar Wind Transients Using IPS.
    Ananthakrishnan, S., Kojima, M., Tokumaru, M., Balasubramanian, V., Janardhan, P., Manoharan, P.K., and Dryer, M. (1999).  Proc. of Solar Wind 9 Conference, AIP, New York. pp 321.
    Eds.  S. R. Habbal 
    
    
98. Fine Structure of the Solar Wind Turbulence Inferred from Simultaneous Radio Occultation Observations at Widely−Spaced Ground Stations. 
    Bird, M.K., Janardhan, P., Efimov, A.I., Samoznaev, L.N., Andreev, V.E., Chashei, I.V., Edenhofer, P., Plettemeier, D., and Wohlmuth, R. (2003).  Solar Wind 10, AIP Conf. Proc. 679, 465−468. AIP Press, Melville, New York, USA., Eds.  M. Velli et al.
    
    
99. Locating the solar source of the extremely low−density, low−velocity solar wind flows of 11 May 1999. 
    Janardhan, P., Fujiki, K., Kojima, M. and Tokumaru, M. (2007).  Proc. of the ILWS Workshop 2006,  p.132−138.
    Eds.     N. Gopalswamy and A. Bhattacharya ISBN:  81−87099−40−2  
    
    
100. Peculiar behavior of solar polar fields during solar cycles 21-23: Correlation with meridional flow speed 
     Susanta Kumar Bisoi, Janardhan,P., (2013).   Proc. IAU Symp. 294,  8, 81−82  (DOI) 10.1017/S1743921313002287. 
     
     
101. Asymmetry in the periodicities of solar photospheric fields: A probe to the unusual solar minimum prior to cycle 24 
     Susanta Kumar Bisoi, Janardhan,P., (2013).   Proc. IAU Symp. 294,  8, 85−86  DOI: 10.1017/S1743921313002305.  
     
     
102. Interplanetary scintillation signatures in the inner heliosphere of the deepest solar minimum in the past 100 years 
     Susanta Kumar Bisoi, Janardhan,P., (2013).  Proc. IAU Symp. 294,  8, 83−84  DOI: 10.1017/S1743921313002299. 
     
     
103. Observations of a geomagnetic SI⁺−SI^-  pair and associated solar wind fluctuations 
     Susanta Kumar Bisoi, Janardhan,P., (2013).   Proc. IAU Symp. 294,  8, 543−544  DOI: 10.1017/S1743921313003141. 
     
     
104. Multi-directional measurements of high energy particles from the Sun-Earth L1 point with STEPS. 
     S.K. Goyal, M.Shanmugama, A. R. Patela, T. Ladiyaa, Neeraj K. Tiwaria, S. B. Banerjeea, S. V.Vadawalea, P. Janardhan,  D. Chakrabartya, R. Srinivas, P. Shuklab, P. Kumara, K. P.Subramaniana, B. Bapat, and P. R. Adhyarua (2016).  Proc. SPIE    9905, doi: 10.1117/12.2232259. 
     
     
105. Long term trends in solar photospheric fields and solar wind turbulence levels: Implications to the near-Earth space 
     Janardhan, P., Fujiki, K., Ingale, M., Susanta Kumar Bisoi and Diptiranjan Rout (2018).  Proc. IAU Symp 340 , 121-124., Doi:10.1017/S1743921318001710 Eds: D. Banerjee, J. Jiang, K. Kusano & S. Solanki
     

(9)  Book Chapters:

1. The Solar Wind and Interplanetary Disturbances.
   Janardhan, P., (2003). Solar Terrestrial Environment  − Space Weather, Allied Publishers, New Delhi., pp. 42−56. Eds.     R.P.Singh, Rajesh Singh & Ashok Kumar, Banaras Hindu University, Varanasi, India.; ISBN:  81−7764−494−7. 

(10) Invited Talks at International and National Conferences ( in chronological order):

1. Estimation of Solar Wind Velocity From the Three-Station IPS Observatory - India. 
   Janardhan, P.
   (Published in the Proc. of the Indo-U.S. Workshop on IPS and Solar Activity - Feb. 1988, pp. 83, Ahmedabad). 


2. Enhanced Scintillation of Radio Source 2204+29 by Comet Austin (1989 c1) at 103 MHz. 
   Janardhan, P., Alurkar, S.K.,Bobra, A.D. and Slee, O.B. 
   (Presented at the 14^th Meeting of the Astronomical Society of India - Jan. 29 to Feb. 1, 1991, PRL, Ahmedabad, India). 


3. A Summary of Radio Observations of Enhanced Scintillations Due to Cometary Ion Tails at 103 MHz. 
   Janardhan, P. 
   (Presented at the Indo-U.S. Workshop on Interplanetary Scintillation and Propagating Disturbances, Ahmedabad, India, Sept. 1991). 


4. Possible Contribution of a Solar Transient to Enhanced Scintillation Due to a Quasar. 
   Janardhan, P. and Alurkar, S.K. 
   (Presented at the Symposium on Solar Connection with Transient Interplanetary Processes (SOLTIP). Sept. 30 to Oct. 5, 1991, Liblice, Czechoslovakia). 


5. Interplanetary Scintillations - Recent Results. 
   Janardhan, P. 
   (Invited Talk - Presented at the National Space Science Symposium (NSSS), March 11−14 1992 at the Physical Research Laboratory, Ahmedabad, India). 


6. A 327 MHz Interplanetary Scintillation Survey of Radio Sources Over 6 steradian. 
   V. Balasubramanian, P. Janardhan and S. Ananthakrishnan. 
   (Presented at the 6^th Asia Pacific Regional Meeting on Astronomy, 16−18 August, 1993, Pune).


7. Unique Observations of PSR 0950+08 and Possible Terrestrial Effects.
   M.R. Deshpande, H.O. Vats, P. Janardhan, A.D. Bobra, Harish Chandra, and G.D.Vyas.
   (Presented at the 6th Asia Pacific Regional Meeting on Astronomy, 16-18 August, 1993, Pune). 


8. Latitudinal Variation of Solar Wind Velocity. 
   Ananthakrishnan, S., Balasubramanian, V., and Janardhan, P.
   (Presented at the 28th ESLAB Symposium " The High Latitude Heliosphere", April, 19−21 1994, Friedrichshafen, Germany). 


9. IPS Observations of the Solar Wind at 327 MHz - A Comparison With Ulysses Observations.
   Janardhan, P., Balasubramanian, V., Ananthakrishnan, S., and Srivatsan, R.
   (Presented at the XVII Annual Meeting of the Astronomical Society of India, January, 17−20, 1996). 


10. On the Nature of Compact Components of Radio Sources at 327 MHz.
    Balasubramanian, V., Janardhan, P., Ananthakrishnan, S. and Srivatsan, R.
    (Presented at the XVII Annual Meeting of the Astronomical Society of India, January, 17−20, 1996). 


11. Radio Observations of Transient Solar Wind Flows.
    Balasubramanian, V., Janardhan, P., Srivatsan, R. and Ananthakrishnan, S.
    (Presented at the third SOLTIP meeting 14−18 October, 1996, Beijing, China). 


12. Measurements of Solar Wind Velocities Close to the Sun Using Ulysses Radio Sounding Data.
    Janardhan, P., Bird, M. K., Edenhofer, P, Plettemeier, D., Wohlmuth, R., Asmar, S W., Patzö lt, M. and Karl, J. 
    (Presented at the XXII General Assembly of the European Geophysical Society, Vienna 21−25 April 1997). 


13. Coronal Velocity Measurements with Ulysses: Multi-link Correlation Studies During two Superior Conjunctions. 
    Janardhan, P., Bird, M. K., Edenhofer, P, Plettemeier, D., Wohlmuth, R., Asmar, S W., Patzö lt, M. and Karl, J. 
    (Presented at the 8th Scientific Assembly of IAGA, Uppsala, Sweden August 4−15, 1997). 


14. K-Band Radio Observations of Comet Hale-Bopp: Detections of Ammonia and (Possibly) Water 
    Bird, M. K., Janardhan, P., Wilson, T. L., Huchtmeier, W.K., Gensheimer, P., and Lemme, C. 
    (Presented at the First International Conference on Hale-Bopp, Puerto de la Cruz, Tenerife, Spain, 2-6 February 1998). 


15. Probing the Interplanetary Medium from the Ground.
    Janardhan, P.
    (Colloquium presented at the Australia Telescope National Facility (ATNF), Sydney, Australia, February, 11 1998). 


16. Cross Correlation Measurements of Coronal Outflow Velocities During Two Solar Conjunctions of the Ulysses Spacecraft. 
    Janardhan, P., Bird, M. K., Edenhofer, P, Plettemeier, D., Wohlmuth, R., Asmar, S W., Patzö lt, M. and Karl, J. 
    (Presented at the 32nd COSPAR Scientific Assembly, Nagoya, Japan, July, 12−19 1998).


17. Anisotropic Structure of the Solar Wind in its Region of Acceleration. 
    Efimov, A.I., Rudash, V.K., Bird, M.K., Janardhan, P. , Patzö lt, M., Karl, J., Edenhofer, P. and Wohlmuth, R. 
    (Presented at the 32nd COSPAR Scientific Assembly, Nagoya, Japan, July, 12−19 1998). 


18. Studying ``Space Weather'' from the Ground. 
    Janardhan, P.
    (Presented at the IV SERC school on Electromagnetic Probing of the Upper Atmosphere, Physical Research Laboratory, Ahmedabad, India, April, 6−29 1998). 


19. The Ulysses Solar Corona Experiment: Coronal Radio Sounding Observations During the Solar Conjunctions in 1992 and 1995. 
    Bird, M.K., Asmar, S W., Edenhofer, P., Janardhan, P ., Karl, J., Patzö lt, M., Plettemeier, D., Volland, H., and Wohlmuth, R. 
    (Presented at the Solar Wind 9, Nantucket Island, Massachusetts, USA, October 5−9, 1998). 


20. Study of Solar Wind Transients Using IPS. 
    Ananthakrishnan, S., Kojima, M., Tokumaru, M., Balasubramanian, S., Janardhan, P., Manoharan, P.K., and Dryer, M.
    (Presented at the Solar Wind 9, Nantucket Island, Massachusetts, USA, October 5−9, 1998). 


21. Studying Solar Generated Heliospheric Disturbances using Interplanetary Scintillation Observations.
    Janardhan, P. 
    (Invited Talk - Presented at the XIX Meeting of the Astronomical Society of India, February 1-4, 1999, RRI, Bangalore, India). 


22. 327 MHz Interplanetary Scintillation Observations during the Whole Sun Month - II Campaign. 
    P. Janardhan., V. Balasubramanian, S. Ananthakrishnan, M. Tokumaru and M. Dryer
    (Presented at the Solar Heliospheric and Interplanetary Environment (SHINE99) Workshop, Boulder, Colorado, USA, June 14−17, 1999). 


23. Observations of Interplanetary Scintillation during the 1998 Whole Sun Month: a comparison between EISCAT, ORT and Nagoya data.
    Moran, P.J., A.R. Breen, A. Canals, R.A. Fallows, P.J.S. Williams, P. Janardhan., M. Tokumaru, J. Markkanen 
    (Presented at the 9th EISCAT International Workshop, Wernigerode/Harz, Germany, September 6−10 1999). 


24. Observations of Interplanetary Scintillation during the 1998 Whole Sun Month: a comparison between EISCAT, ORT and Nagoya data.
    Moran, P.J., Ananthakrishnan, S., Balasubramanian, V., Breen, A.R., Canals, A., R.A. Fallows, P. Janardhan., Tokumaru, M., and Williams, P.J.S. 
    (Presented at the XXV General Assembly of the European Geophysical Society, Nice, France, April 2000). 


25. Radio Detection of a Rapid Disturbance Launched by a Solar Flare.
    Janardhan P., White, S.M., and Kundu, M.R. 
    (Presented at the International Conference on Solar Eruptive Events, March 6−9, 2000, Catholic University of America, Washington, DC, USA). 


26. The Role of IPS Technique in Detection and Tracking of Interplanetary Transients and its Application to Short Term Forecasts of Space Weather 
    Balasubramanian, V., Ananthakrishnan, S., Janardhan, P . and Dryer, M. 
    (Presented at the Chapman Conference on Space Weather: Progress and Challenges in Research and Applications. March 20-24, 2000). 


27. Subsidence of Solar Wind Over a Large Part of the Inner Heliosphere Monitored by IPS During 3 - 16 May 1999. 
    Balasubramanian, V., Ananthakrishnan, S., Janardhan, P . and Srinivasan, S. 
    (Presented at the ISTP Science Workshop - Goddard Space Flight Centre, Maryland, USA, March 27-30, 2000 at the special session on "The Day the Solar Wind Went Away"). 


28. A Comparitive Study of Scintillation Data from EISCAT, ORT and Nagoya during the 1998 and 1999 Whole Sun Months. 
    P.J. Moran, S. Ananthakrishnan, S. Balasubramanium, A.R. Breen, A. Canals, R.A. Fallows, P. Janardhan, M. Tokumaru and P.J.S. Williams. 
    (Presented at the European Geophysical Society XXV General Assembly, Nice, April 25-29 200). 


29. An Extremely Rapid Solar Flare Associated Disturbance Observed at 333 MHz.
    Janardhan, P., White, S.M., and Kundu, M.R. 
    (Presented at the Solar Physics Division (SP Annual Meeting, Lake Tahoe, USA, June 19-22, 2000). 


30. Living With a Star - The Sun.
    Janardhan, P.
    (Invited Talk - Presented at the Workshop on Meteors, Astroids and Planets, PRL, Ahmedabad, India, February 26-March 2, 2001). 


31. Subsidence of Solar Wind Over a Large Part of the Inner Heliosphere Monitored by IPS During 3− 16 May 1999.
    Janardhan, P. 
    (Presented at the Conference on "Probing the Sun with High Resolution" Udaipur Solar Observatory, PRL, Udaipur, India, October 16−12, 2001). 


32. Understanding the Sun-Earth Connection.
    Janardhan, P.
    (Invited Talk - Presented at the XII National Space Science Symposium, Barkatulla University, Bhopal, India, February 25-28, 2002). 


33. Interplanetary Scintillation Observations of the Large-Scale Solar Wind Subsidence Event of May 1999. 
    Janardhan, P., Balasubramanian, V., and Ananthakrishnan, S.
    (Presented at the First STEREO Workshop "The 3-D Sun and Inner Heliosphere: The STEREO View" Paris, March 18−20, 2002). 


34. Fine Structure of the Solar Wind Turbulence Inferred from Simultaneous Radio Occultation Observations at Widely-Spaced Ground Stations. 
    Bird, M.K., Janardhan, P., Efimov, A.I., Samoznaev, L.N., Andreev, V.E., Chashei, I.V., Edenhofer, P., Plettemeier, D., and Wohlmuth, R. 
    (Presented at the Solar Wind 10 Conference, Pisa, Italy, 17−21 June 2002). 


35. Remote Sensing Interplanetary Disturbances. 
    Janardhan, P.
    (Invited Talk - Presented at the Workshop on "Radio and Optical probing of the Upper Atmosphere", PRL, Ahmedabad, India, February 6−8, 2003). 


36. IPS Observations with the Ooty Radio Telescope
    Janardhan, P.
    (Invited Talk - Presented at the Symposium Entitled "ORT: Past Present and Future", Radio Astronomy Centre, Ooty, April 17−19 2003). 


37. Magnetic Solar Cycle Related Heliospheric Density Anomalies 
    Ananthakrishnan, S., Janardhan, P and Balasubramanian, V.
    (Presented at the IAU General Assembly, Sydney, Australia, July 2003). 


38. Radio Observations of Rapid Acceleration in a Slow Filament Eruption/Fast CME Event.
    Kundu, M.R., White, S.M., Garaimov, V.I., Manoharan, P.K., Prasad Subramanian, Ananthakrishnan, S., and Janardhan, P.
    (Presented at the fall meeting of the AGU, 2003). 


39. Enigmatic Solar Wind Disappearance Events: Insights from IPS Observations
    Janardhan, P. .
    (Invited Talk -Presented at the Conference on "Sun Earth Connections: Multiscale Coupling of Sun-Earth Processes", Hawaii, USA, Feb. 9−13 2004). 


40. Resolving the Enigmatic Solar Wind Disappearance Event of 11 May 1999.
    Janardhan, P.
    (Invited Talk - Presented at the First Asia Oceanic Geophysical Society (AOGS Meeting, Singapore, July 5−9 2004).


41. Meterwave Observations of the Solar Corona with the Giant Meterwave Radio Telescope (GMR and the Nancay Radio Heliograph (NRH).
    Prasad Subramanian, Claude Mercier, Alain Kerdraon, Monique Pick, S. Ananthakrishnan and Janardhan, P.
    (Presented at the XXVIII General Assembly of the International Union of Radio Science (URS, New Delhi, India, Oct. 23−29, 2005). 


42. Locating the solar source of the extremely low-density, low-velocity solar wind flows of 11 May 1999
    Janardhan, P., Fujiki,K., Kojima, M. and Tokumaru, M.
    (Invited Talk - Presented at the ''ILWS Workshop - The Solar Influence on the Heliosphere and Earth's Environment: Recent Progress and Prospects" Goa, India, Feb. 19−24, 2006). 
43. Low Density Solar Wind Anomalies. 
    Janardhan, P. 
    (Invited Talk - Presented at the International Colloquium "Scattering and Scintillation in Radio Astronomy", 19−23 June 2006, Pushchino, Moscow, Russia). 


44. Electron acceleration in solar noise storms 
    Prasad Subramanian, Peter A. Becker, Claude Mercier, Steve White, Alain Kerdraon, Monique Pick, S. Ananthakrishnan, P. Janardhan
    (Presented at the second UN/NASA workshop on the International Heliophysical Year and basic Space Science , IIAP, Bngalore Nov. 27−Dec. 1 2006). 


45. Solar observations during solar minima with Brazilian Decimetric Array. 
    J.F. Valle, R. Ramesh, P. Janardhan , J. R. Cecatto and H. S. Sawant.
    (Presented at the Eighth Latin American Conference on Space Geophysics (VIII -COLAG Mexico, July 17−21, 2007). 


46. Studies of Long Lasting Low Density Solar Wind Anomalies at 1 AU. 
    P. Janardhan, J. F. Valle and H. S. Sawant
    (Presented at the Eighth Latin American Conference on Space Geophysics (VIII -COLAG Mexico, July 17−21, 2007 ). 


47. The Solar Wind Disappearance Event of 11 May 1999: Source Region Evolution. 
    Mason, H.E., Janardhan, P., and Tripathi, D.
    ( Presented at the National Astronomy meeting of the Royal Astronomical Society, 31 March−04 April 2008, Queens University Belfast, UK). 


48. Source Region Evolution of the Solar Wind Disappearance Event of 11 May 1999 
    Janardhan, P., Tripathi, D. & Mason, H.E.
    ( Presented at the European Solar Physics Meeting (ESPM12), 8−12 September 2008, Freiburg, Germany). 


49. The Global Electromagnetic Moon Surveyor. 
    S. Ananthakrishnan, J. E. S. Bergman, L. Blomberg, F. Bruhn, T. D. Carozzi, L. K. S. Daldorff, A. I. Eriksson, S. Gurubaran, N. Ivchenko, P. Janardhan, P. Kale, V. Korepanov, J. Lazio, H. Lundstedt, A. Marusenkov, S. M. Mohammadi, H. Rothkaehl, B. Thidé, J.-E. Wahlund, K. Weiler, and L. Åhlén.
    ( Presented at the DGLR International Symposium “To Moon and beyond", 15−17 September, 2008, Bremen, Germany). 


50. When the Solar Wind Vanishes: Causes on the Sun, Effects at the Earth. 
    Janardhan, P. .
    (Invited Talk -Presented at the 27th ASI Meeting, February 18 − 20, 2009, Bangalore, India. ). 


51. The Deepest Solar Minimum in 100 Years: Earliest Inner Heliospheric Signatures 
    Janardhan, P. .
    (Invited Talk -Presented IUCAA, Pune, Sept. 4−7 2011 ). 


52. Declining solar activity in solar cycles 22 and 23 and their inner heliospheric signatures 
    Janardhan,P., (2012). 
    ( Presented at the 39th COSPAR meeting, July 14-22, 2012, Mysore, India ). 


53. Quasi-periodic variations in solar photospheric fields in the build-up to the deep minimum between solar cycles 23 and 24. 
    Janardhan,P., (2012). 
    ( Presented at the International Symposium on Solar Terrestrial Physics, November 6-9, 2012, IUCAA, Pune, India). 


54. Earliest Solar and Heliospheric Signatures of the Build-up to the Deepest Solar Minimum in 100 years 
    Janardhan,P., (2012). 
    ( Presented at Workshop on Coronal Magnetism - Connecting Models to Data and the Corona to the Earth", May 2012, Boulder, CO, USA.) 


55. Extremely low density solar wind events observed at 1 AU and their space weather consequences. 
    Janardhan, P. .
    (Invited Talk -Presented at the High Altitude Observatory, Boulder, Colorado, USA, 31 May 2012 ). 


56. Peculiar behavior of solar polar fields during solar cycles 21-23: Correlation with meridional flow speed 
    Susanta Kumar Bisoi, Janardhan,P., (2013).  Proc. IAU Symp. 294,   8, 81−82  (DOI) 10.1017/S1743921313002287.
    ( Presented at the IAU Symposium 294“Solar and Astrophysical Dynamos and Magnetic Activity", August, 2012, Beijing, China). 


57. Asymmetry in the periodicities of solar photospheric fields: A probe to the unusual solar minimum prior to cycle 24
    Susanta Kumar Bisoi, Janardhan,P., (2013).  Proc. IAU Symp. 294,   8, 85−86  (DOI) 10.1017/S1743921313002305.
    ( Presented at the IAU Symposium 294“Solar and Astrophysical Dynamos and Magnetic Activity", August, 2012, Beijing, China). 


58. Interplanetary scintillation signatures in the inner heliosphere of the deepest solar minimum in the past 100 years
    Susanta Kumar Bisoi, Janardhan,P., (2013).  Proc. IAU Symp. 294,   8, 83−84  (DOI) 10.1017/S1743921313002299.
    ( Presented at the IAU Symposium 294“Solar and Astrophysical Dynamos and Magnetic Activity", August, 2012, Beijing, China). 


59. Observations of a geomagnetic SI⁺−SI^- pair and associated solar wind fluctuations
    Susanta Kumar Bisoi, Janardhan,P., (2013).  Proc. IAU Symp. 294,    8, 543−544 (DOI)  10.1017/S1743921313003141.
    ( Presented at the IAU Symposium 294“Solar and Astrophysical Dynamos and Magnetic Activity", August, 2012, Beijing, China). 


60. The deepest solar minima in 100 years : Heliospheric micro-turbulence levels from 327 MHz IPS observations and periodicities in solar photospheric fields 
    Janardhan,P.,Susanta Kumar Bisoi, Chakrabarti, D.and Ananthakrishnan, S. (2013). 
    ( Presented at the Asia-Pacific regional URSI conference, Taipei, Taiwan, September 3−7, 2013 ). 


61. Steady decline in solar polar magnetic fields and heliospheric microturbulence levels: Are we headed towards a Maunder minimum?
    Susanta Kumar Bisoi  Janardhan, P.  and S. Ananthakrishnan, (2014).
    (Presented at the 40th General Assembly, Beijing, China, August 16−23, 2014 ) 

62. Declining Solar Polar Fields and Heliospheric Micro-turbulence: Are we Heading Towards Another Maunder Minimum?
    Janardhan, P.
    (Invited talk – Presented at the conference on  Plasma Processes in Solar and Space Plasmas at Diverse Spatio-Temporal Scales: Upcoming Challenges in Science and Instrumentation, 26-28 Mar. 2014)

63. Are we on the verge of a Maunder –Like Grand Solar Minimum
    Janardhan, P.
    (Invited talk  - Presented at the CSPM 2015 – “Ground Based Solar Observations in the Space Instrumentation Era” - Coimbra, Portugal, 5-9, October 2015.”

64. A 20 year decline in solar magnetic fields – heliospheric response and possible consequences?
    Janardhan, P.
    (Invited Talk – Presented at the conference on “New Paradigms for the Heliosphere'', Physikzentrum Bad Honnef, Germany, 29 June - 03 July 2015.

65. Are we on the verge of a Maunder –Like Grand Solar Minimum
    Janardhan, P.
    (Invited Colloquium   - - MPIFR –   Bonn, Germany, 26 June 2015)

66. Declining Solar Polar Fields and their Signatures in the Solar Wind: Implications to near Earth Space
    Janardhan, P.
    (Invited talk -  1st URSI Atlantic Radio Science Conference (URSI AT-RASC), Gran Canaria, May 18 - 22, 2015)

67. Declining  Solar Photospheric Magnetic fields and Solar wind Micro-turbulence
    Janardhan, P.
    (Invited talk - Presented at the Dynamic Sun: II. Solar Magnetism from Interior to the Corona, Cambodia, Feb 12-16, 2018).

68. Solar Activity - Past, Present and Near Future
    Janardhan P
    ( Invited Talk -Presented at the ISRO Structured Training Program (STP) in Space Sciences – PRL, March 5--9, 2018).

69. The Sun-Earth Connection
    Janardhan P
    ( Plenary Talk - Presented at the National Symposium on "Advancements in Geospatial Technology for Societal Benifits", Space Application Centre, Ahmedabad, 5--7 December 2018).

70. Beyond the Mini Solar Maximum of Cycle 24: The Amplitude of Solar Cycle 25 and the Evolution of the Terrestrial Magnetosphere
    Janardhan P
    ( Invited Talk -Presented at the National Space Science Symposium, Savitri Bhai Phule University, Pune, 29-31, January 2019).

71. Solar Polar Fields During Cycle 24: An Unusual Polar Field Reversal.
    Janardhan P  and Susanta Kumar Bisoi
    ( Presented at the URSI Asia Pacific Radio Science Conference 2019, (APRASC 2019) New Delhi, 9-15, March 2019).

72. High Resolution Imaging of Coronal Type III Bursts: First MUSER Solar Radio Observations.
     Susanta Kumar Bisoi, and Janardhan P
    ( Presented at the URSI Asia Pacific Radio Science Conference 2019, (APRASC 2019) New Delhi, 9-15, March 2019).

73. A Decimetric Emission Source 500^'' away from a Flaring Site.
     Susanta Kumar Bisoi, and Janardhan P
    ( Presented at the URSI Asia Pacific Radio Science Conference 2019, (APRASC 2019) New Delhi, 9-15, March 2019).

74. Declining solar polar fields, the terrestrial magnetosphere and the forthcoming solar cycle
    Janardhan P
    ( Invited talk - Presented at the workshop on International Space Weather Initiative (ISWI) in collaboration with the United Nations Office of Outer Space Affairs during May 20-24, 2019).

(11) Organisation of Conferences:

1. 2nd URSI Regional Conference on Radio Science 2015 (URSI-RCRS 2015) New Delhi, India, from 16 to 19 November 2015.


2. APRASC- 2019: URSI Asia-Pacific Radio Science Conference (AP-RASC 2019 ) New Delhi, India from 09 – 15 March, 2019.

(12) National and International scientific collaborations:

       Have active Collaborations with Cambridge, UK, ISEE Japan, NAO Beijing, NCRA, TIFR, India

(13)Important Scientific Contributions:

• I am the PI of the Aditya Solar Wind Particle Experiment (ASPEX), payload selected for the ISRO ADITYA-L1 mission to be tentatively launched in 2020.  The payload will study particle fluxes and anisotropies in the energy range 100 eV to 20 MeV.


• My work provided the first effective observational tool to predict geo-effective co-rotating interaction region (CIR) out flows based on the fact that solar wind flow angle determines the geo-effectiveness of CIR. This now provides a lead time of up to 30 minutes take appropriate preventive action to protect space based assets from being damaged due events having a solar and solar wind origin.


• By careful analysis of magnetic field data, I demonstrated a steady decline in solar magnetic fields and inner-heliospheric micro-turbulence for past two decades, with attendant climatic effects, suggesting that the Sun is probably approaching another prolonged Solar Minimum like the Maunder minimum when the Sun was devoid of sunspots during the period 1645-1715. 


• My work has also established a 2.5 year asymmetry in the time of reversal of solar polar fields in cycle 24 with the solar Northern hemisphere having reversed its polarity 2.5 after the field reversal in the Southern hemisphere.


• The above study also established prolonged low night time F-region electron densities in solar cycle 23.  This opens up a new and hitherto inaccessible radio window for ground-based radio observations well below the ionospheric cut-off frequency of 30 MHz.


• My work provided the first unambiguous direct correlation between enhancement of solar wind density outside the earth’s magnetosphere and magnetic measurements at the ground.


• My work has shown that the stand-off point of the earth’s magnetosphere, on the sunward side, has expanded outwards by 1 full earth radii since 1995, due to the extremely low solar wind dynamic pressure in the past two decades.


• My work identified the solar sources and causes of disappearance events of solar wind, and provided the first mechanism between the Sun and space weather events at 1 AU, caused exclusively by non-explosive solar events.


• Our work on density turbulence in the solar wind obtained a comprehensive palette of results concerning the heliocentric dependence of the density turbulence spectral amplitude and the density modulation index in the solar wind.


• I have developed a novel method based on interplanetary scintillation (IPS) observations coupled with simple model based predictions to track interplanetary disturbances from the sun to the earth and have also used IPS observations at 103 MHz to determine contribution of interstellar scattering (ISS) to radio source size broadening at 103 MHz and to confirm enhanced scattering in the plane of the Galaxy.


• I have used the 100m telescope at Effelsberg, Germany to unambiguously detect radio emission in Comet Hale-Bopp from ammonia, a suspected parent molecule in comets.  Hale-Bopp was near its perihelion passage at the time of observation.  Signals from the five lowest metastable inversion transitions of ammonia were obtained to derive a rotational temperature of 104±30 K, assumed to be representative of the kinetic temperature in the comet’s inner coma (R < 5000 km). The ammonia production rate at perihelion calculated from these observations are 6.6±1.3 × 10²⁸ s⁻¹ (almost two tons of ammonia per second). Compared with independently determined water production rates near perihelion, the implied ammonia abundance ratio to water is in the range 1.0–1.8%.  A near detection of water was also made


• I have successfully shown that cometary ion tails, under specific conditions of observing geometry, can produce interplanetary scintillation at the ground, thereby providing one a means of studying the densities and velocities in cometary ion tails well downstream of the cometary nucleus.


• Using Ulysses Radio Sounding data of the solar corona enabled me to examine the densities and velocities in the solar corona in the acceleration region of the solar wind in the distance range 4-40 solar radii.  This is a region not accessible by any other means.


• Radio visibilities from the Giant Meterwave Radio Telescope (GMRT), India and the Nancay Radio Heliograph (NRH), France have been successfully combined to produce solar images with unprecedented resolutions at 327 MHz (~30 arcsec).  This allowed us to study, for the first time, the structure of solar radio noise storms which are very compact sources of radio emission on the sun.


• I have reported the direct observation of motion associated with a solar flare at a speed of 26,000 km s^-1. The motion K is seen from a radio source at 0.33 GHz, which suddenly starts moving during the flare. The disturbance itself does not seem to radiate, but it excites coronal features that continue to radiate after it passes. The inferred velocity is larger than any previously inferred velocity of a disturbance in the solar atmosphere apart from freely streaming beams of accelerated electrons. The observed motion of the source at a fixed frequency, low polarization, and  moderate bandwidth are more consistent with the typical properties of moving type IV radio bursts than with classical coronal shock–associated type II bursts, but any disturbance at such a high velocity must be highly supersonic O and should drive a shock. We speculate that the disturbance is associated with the realignment of magnetic fields connecting different portions of an active regions. 


• My work has shown how radio emission often seen far away from a flaring site can now be explained by the ducting effect.

(14) Some important contributions have been highlighted and briefly described below:

1. The Geo-effectiveness of Solar Wind Flows Caused By Co-rotating Interaction Regions

Important Findings:

• A systematic study of Co-rotating Interaction Regions has shown that their geo-effectiveness is governed by their azimuthal or non-radial flow angle.  Only those CIR associated solar wind flows that deviate with respect to the radial direction by less than 6^o in the azimuthal plane are seen to be geo-effective and show a causal relationship between Bz and the equatorial electrojet (EEJ). 
• This provides a quick way to predict Geo-effective solar wind outflows from L1 and is the first observational method of predicting geo-effectiveness with a lead time of 30 minutes to an hour.

Impact on the Field:

This is for the first time ever that we have an observational parameter to specify if a given solar wind outflow observed at L1 and associated with co-rotating interaction regions will have an impact on the terrestrial magnetosphere or in other words be geo-effective.  This work was also reported in Nature India under the title “A new angle on the effects of solar wind” - doi:10.1038/nindia.2017.116.

CIR’s and Geo-effectiveness

The magnetic field in the heliosphere continuously evolves in response to the solar photospheric field at its base. Together with the rotation of the Sun, this evolution drives space weather through the continually changing conditions of the solar wind and the magnetic field embedded within it.  The aim of space weather studies has therefore been to try and predict the geo-effectiveness of solar wind streams interacting with the terrestrial magnetosphere and ionospheric system.  In other words, space weather studies try to establish a causal relationship between solar wind events or disturbances taking place outside the terrestrial magnetosphere with events occurring within the terrestrial magnetosphere or the earth’s ionosphere. 

Solar rotation coupled with the fact that solar wind streams can have different flow velocities will yield interaction regions, in the inner-heliosphere, where the different flow streams will interact. Such interaction regions are commonly referred to as co-rotating interaction regions (CIR) and are identified by rapid fluctuations in the z-component of the interplanetary magnetic field (Bz).  We have identified a large number of such CIR’s at the L1 Lagrangian point of the sun-earth system and shown that their geo-effectiveness is governed by their azimuthal or non-radial flow angle.  Interestingly, only those CIR associated solar wind flows that deviate with respect to the radial direction by less than 6o in the azimuthal plane are seen to be geo-effective and show a causal relationship between Bz and the equatorial electrojet (EEJ). 

These results thus, provide one an easy and quick method of predicting the geo-effectiveness of solar wind outflows by merely examining their degree of deviation from the radial direction.

2. A long-term study of declining solar photospheric magnetic fields: inner-heliospheric signatures and possible implications

Important findings:

• This study indicates that a grand minimum akin to a Maunder like minimum may be in progress if the decline in solar fields continues beyond 2020.
• Solar photospheric fields and solar wind micro-turbulence levels have been steadily declining from ~1995 and the decline is continuing.  The declining trend is likely to continue at least until the minimum of cycle 24 in 2020. 
• The heliospheric Magnetic Field, based on the correlation between the high-latitude magnetic field and the HMF at the solar minima, is expected to decline to a value of ~4.0 (±0.6) nT by 2020.
• The peak 13 month smoothed sunspot number of Cycle 25 is likely to be ~69 ± 12, thereby making Cycle 25 a slightly weaker cycle than Cycle 24, and only a little stronger than the cycle preceding the Maunder Minimum and comparable to cycles in the 19th century.
• Solar cycle 24 showed pronounced asymmetry in the polar field reversals between the two solar hemispheres with the northern hemisphere reversing polarity 2.5 years after the southern hemisphere.

Impact on the field:

The study predicts the onset of a Maunder like grand minimum, with all the associated climate effects, if the decline in solar fields continues beyond 2020.   This is a very significant conclusion as the last Grand minimum occurred over 400 years ago and we will have the opportunity to study it in detail.

Declining solar photospheric fields

Sunspots or dark regions of strong magnetic fields on the sun are generated via magneto-hydrodynamic processes involving the cyclic generation of toroidal, sunspot fields from pre-existing poloidal fields and their eventual regeneration through a process, referred to as the solar dynamo. This leads to the well known and periodic 11-year solar cycle of waxing and waning sunspot numbers. However, studies of past sunspot activity reveal periods like the Maunder minimum (1645—1715) when the sunspot activity was extremely low or virtually non-existent.  Using ¹⁴C records from tree rings going back 11, 000 years in time, 27 such prolonged or grand solar minima have been identified, implying that conditions existed in these 17% - 18% of solar cycles to force the sun into grand minima.  The current solar cycle 24 was preceded by one of the deepest solar minima in the past 100 years, with sunspot numbers continuously remaining well below 25, and thereby causing cycle 24 to start ~1.3 years later than expected.  Also, solar cycle 24, with a peak smoothed sunspot number ~75 in November 2013, has been the weakest since cycle 14 in the early 1900's.

The work on solar photospheric magnetic fields, using synoptic magnetograms from the National Solar Observatory (NSO), Kitt Peak (NSO/KP), between 1975—2010, spanning the last three solar cycles, have shown a steady decline in solar photospheric magnetic fields at helio-latitudes (≥45^ο) until 2010, with the observed decline having begun in the mid-1990's.  Also, recent studies of the sunspot umbral field strengths have shown that it has been decreasing by ~50 G per year.  It is known that for field strengths below about 1500 G, there would be no contrast between the photosphere and sunspot regions, thereby making the later invisible.  Some authors have claimed that the umbral field strengths in cycle 25 would be around 1500 G, and thus there would be very little/no sunspots visible on the solar photosphere.  Studies of the heliospheric magnetic fields (HMF), using in-situ measurements at 1 AU, have also shown a significant decline in their strength.  In addition, using 327 MHz observations from the four station IPS observatory of the Institute of Space Earth Environmental Sciences (ISEE), Nagoya University, Japan, we have examined solar wind micro-turbulence levels in the inner-heliosphere and have found a similar steady decline, continuing for the past 18 years, and in sync with the declining photospheric fields.  A study, covering solar cycle 23, of the solar wind density modulation index, Є_N ≡ ∆N/N, where, ∆N is the rms electron density fluctuations in the solar wind and N is the density, has reported a decline of around 8% from which the authors attributed to the declining photospheric fields.

In light of the very unusual nature of the minimum of solar cycle 23 and the current weak solar cycle 24, the nominee re-examined solar photospheric magnetic fields between 1975—2013, the HMF between 1975—2014, and the solar wind micro-turbulence levels between 1983—2013. He estimated the peak sunspot number of solar cycle 25 and addressed the question of whether we are heading towards a grand minimum much like the Maunder minimum. The cyclic magnetic activity of the Sun, manifested via sunspot activity, modulates the heliospheric environment, and the near-Earth space. It was, therefore, felt that it was imperative that one examine how the recent changes in solar activity have influenced the near-Earth space environment.  He therefore examined the response of the Earth's ionosphere, for the period 1994—2014, to assess the possible impact of such a Maunder minimum on the Earth's ionospheric current system.

It may be noted that a recent study, reported that the solar activity in Cycle 23 and that in the current Cycle 24 is close to the activity on the eve of Dalton and Gleissberg-Gnevyshev minima, and claimed that a Grand Minimum may be in progress. Also, a recent analysis of yearly mean sunspot-number data covering the period 1700 to 2012 showed that it is a low-dimensional deterministic chaotic system. Their model for sunspot numbers was able to successfully reconstruct the Maunder Minimum period and they were hence able to use it to make future predictions of sunspot numbers. Their study predicts that the level of future solar activity will be significantly decreased leading us to another prolonged sunspot minimum lasting several decades. The study by the nominee, on the other hand, using an entirely different approach, also suggests a long period of reduced solar activity.

Modeling studies of the solar dynamo invoking meridional flow variations over a solar cycle have successfully reproduced the characteristics of the unusual minimum of sunspot cycle 23 and have also shown that very deep minima are generally associated with weak polar fields. Attempts to model grand minima, seen in ~11000 years of past sunspot records using ¹⁴C data from tree rings have found that gradual changes in meridional flow velocity lead to a gradual onset of grand minima while abrupt changes lead to an abrupt onset.  In addition, these authors have reported that one or two solar cycles before the onset of grand minima, the cycle period tends to become longer.  It is noteworthy that surface meridional flows over cycle 23 have shown gradual variations from 8.5 ms^-1 to 11.5 ms^-1 and 13.0 ms^-1 (Hathaway and Rightmire, 2010) and cycle 24 started ~1.3 years later than expected.  There is also evidence of longer cycles before the start of the Maunder and Sporer minimum. It may also be noted that the current cycle 24 is already weak and the analysis by the nominee suggests a similar weak cycle 25. All these indicate that a grand minimum akin to a Maunder like minimum may be in progress.

3. Implications of the declining solar photospheric magnetic fields on the ionosphere:

Important findings:

• The observations of a significant correlation between the night time F2-region electron density and sunspot number show that the night time ionospheric cut-off frequency has dropped well below 10 MHz in solar cycle 23. 

• It is for the first time such an assessment has become possible using ionospheric data as the existence of the ionosphere itself was not known during the previous grand solar minimum. It is known that F-region densities go through a solar like cycle and are low during low solar activity. 
• Our data indicate that these would be at their lowest during an impending minimum that would stay for an extended period of several years. 

Impact on the field:

The results obtained establish that such prolonged low levels of night time F-region electron densities will open up the low-frequency radio window and be a boon to radio astronomy for ground-based studies of the high red-shift radio universe well below 10 MHz. Currently, the lowest observing frequencies in India are 40 MHz for solar studies and 150 MHz for extra-galactic studies.

Since sunspots in conjunction with the polar field, modulates the solar wind, the heliospheric open flux and the cosmic ray flux at earth, an impending long, deep solar minimum is likely to have a terrestrial impact in terms of climate and climate change.  Once the interplanetary magnetic field goes through a low, it would modulate the flux of galactic cosmic rays (GCR) that arrive at the earth and there exists positive evidence for GCR's to act as cloud condensation nuclei thus enabling precipitation of rain bearing clouds. So the rain fall is likely to be impacted, though it would be very difficult to quantify this change.  Such observations suggest that a cosmic ray-cloud interaction may help explain how changes in solar output can produce changes in the Earth's climate. 

4. Determining the cause of Solar Wind Disappearance Events

Important findings:

• A very significant finding in this study is that apart from co-rotating interaction regions, disappearance events are the only other non-explosive solar events that can cause space weather effects at 1 AU.
• Disappearance events are solar surface phenomena that originate at short-lived active-region-coronal-hole (AR-CH) boundaries located at central meridian on the Sun. 
• These events are not linked to global solar events like solar polar field reversals, as speculated by many other researchers and are all associated with highly non-linear solar wind flows and extended Alfvén radii. 
• The model proposed by the nominee invokes interchange reconnection processes driven by large magnetic flux expansion factors (between 100 - 1000) at the solar source region and is the first and only one to satisfactorily explain all the observational peculiarities of disappearance events at 1 AU. 

Impact on the field:

Solar wind disappearance events are very rare large-scale density anomalies in the interplanetary medium when the average solar wind densities at 1 AU drop by over two orders of magnitude for periods exceeding 24 hours.  The nominee has, in a series of papers provided the first comprehensive understanding of these unique events. 

5. Unambiguous detection of Solar Wind Density enhancements in Ground Magnetic Measurements:

Important findings:

• A study of one of the longest recorded southward interplanetary magnetic field (IMF Bz) conditions (44 hours) in May 1998 led to the identification of multiple solar wind density enhancements observed at 1 AU. These density pulses, observed at the L1 Lagrangian point of the sun-earth system and lying well outside the earth’s magnetosphere showed a distinct one-to-one correspondence with ground magnetic responses during 0700–1700 UT on May 03, 1998. 

Impact on the field:

This is the first ever clear instance of a “Space-Weather” event where there is an unambiguous one-to-one correlation between density pulses in the solar wind, well outside the earth’s magnetosphere, and ground magnetic measurements. 

6. Tracking interplanetary disturbances from the sun to the earth.

Important findings:

• Extensive IPS observations, with the Ooty Radio Telescope (ORT) have been used to evolve a unique technique to track interplanetary (IP) disturbances through space from day-to-day.  The technique, known as the “picket-fence” method, first uses a theoretical model to predict the location in space of a flare generated shock and then uses the IPS sources as a rapidly movable picket fence in the sky to pinpoint and track the propagating shock front between 0.2 and 0.8 AU. 

Impact on the field:

This method was the first successful day-to-day tracking of IP disturbances with the ORT.  The uniqueness of the method lies in the fact that the locations in space of temporally distinct IP transients were predicted in advance by a simple theoretical model of propagation of IP shocks, based on real-time observations of temporally separated events on the Sun.  Signatures of these shocks were then detected unambiguously using IPS observations on a large grid of spatially distributed compact radio sources that were used as a rapidly movable picket-fence in the sky.

7. Probing the Inner Scale of the Turbulent Spectrum in the Solar Wind.

Important findings:

• Finding the dissipation scale or inner scale of the turbulent spectrum is one of the most important problems in understanding turbulence in the solar wind. 
• We have examined the turbulent spectrum in the distance range 0.2 to 0.8 AU using interplanetary scintillation (IPS) observations and shown that that the length scales probed by the IPS technique are larger than the inner scale only if the inner scale is the electron gyro radius.
• If it is due to proton cyclotron resonance, and the density is given by the fourfold Newkirk model.

Summary:

IPS observations at 327 MHz were used to infer density fluctuations of spatial scales of 50 to 1000 km, a range of scale sizes that the IPS technique is sensitive to.  We examined how these scales relate to the dissipation scale of the turbulent cascade, often referred to as the inner scale of turbulent fluctuations.  If the length scales probed by the IPS technique are in the inertial range, it is reasonable to presume that the magnetic field is frozen-in, and the density fluctuations can then be taken as a proxy for magnetic field fluctuations. 

In order to investigate this issue, we considered three popular inner scale prescriptions.  One prescription for the inner scale assumes that the turbulent wave spectrum is dissipated due to ion cyclotron resonance, and the inner scale is the ion inertial scale.  A second prescription identifies the inner scale with the proton gyro-radius.  The third prescription considered is, therefore, one where the inner scale is taken to be equal to the electron gyro-radius. We have used electron and proton temperatures of 105K in order to compute the proton and electron gyro radii respectively.  The magnetic field is taken to be a standard Parker spiral.  In order to compute the inner scale using we need a density model.  We have used two representative density models -- the Leblanc density model and the fourfold Newkirk density model. 

8. Decimetric emission 500² away from a flaring site: Wave Ducting Effect from GMRT solar radio observations

Important Findings:

• In the present work, we have used high temporal and spatial radio images, produced using GMRT 610 MHz observations obtained during a C1.4 class solar flare on 20 June 2015. We have reported a strong decimetric radio source, located far from the flaring active region. Also, we have reported weak decimetric radio sources identified during the 610 MHz flare maximum.  The weak radio sources are however, located near the flaring site. Further, they show a close temporal correlation with the strong radio source and as well with the metric type-III radio bursts identified in the SBRS/YNAO metric dynamic spectra. 
• Based on our investigation of a multi-wavelength analysis and PFSS extrapolations, we have suggested that the source electrons of decimetric radio sources and metric type-III bursts originated from a common electron acceleration site located near the flaring active region.
• It’s location far from the flaring site is presumably caused by the wave ducting of the emitted coherent radio waves, that escaped along the a connected high arching magnetic loop to the remote location.

Impact on the field:

Flare-associated streaming electrons, while propagating in a density depleted tube, can pitch-angle scatter by the enhanced turbulent Alfv´en waves. As a result, the electrons exhibit a velocity distribution, which is unstable to electron Cyclotron Maser(ECM) instability. It is likely that the flare-associated upward streaming electrons, in this case, after pitch-angle scattered by the turbulent Alfv´en waves, could have resulted in an ECM instability. The instability, in turn, would have generated o- or x-mode electromagnetic waves near the second harmonic of the gyro-frequency, that is, at 610 MHz.  Our work thus shows how radio emission observed in completely quiet regions of the photosphere with no apparent source can now be explained.

9. Synthesis Imaging of the Quiet Sun by Combining GMRT and Nancay Radioheliograph Observations

Summary:

To exploit the complementary uv coverage and capabilities of the Giant Meterwave Radio Telescope (GMRT) and the Nancay Radio Heliograph (NRH) we carried out coordinated observations of the sun. The aim was to combine the visibilities produced by the GMRT and the NRH and thereby produce synthesis images for the quiet sun and snapshot images for noise storms and bursts.  The resulting images will have a very high dynamic range and resolution. Observations of small sources can constrain parameters of the turbulent spectrum in the corona.  Using this method we studied compact radio noise storms at meter wavelengths and obtained unprecedented resolutions of ~31 arc sec at 327 MHz, thus enabling us to study the structure, for the first time, of compact radio noise storms.

Impact on the field:

We produced composite 17 s snapshot images (from actual observations of the sun on Aug. 27, 2002) of structures between 60 and 200 arcsec in size with a resolution of 49 arcsec and rms dynamic ranges of 250–420. The quality of the composite image is far better than those of images from the individual instruments.

To the best of our knowledge, these are the highest dynamic range snapshot maps of the sun at meter wavelengths. Until now, high dynamic range radio maps of the sun were typically made by synthesis imaging over time periods of a few hours. High dynamic range images would be essential in studying phenomena like bright radio bursts occurring along with (fainter phenomena like) coronal mass ejections.

Exploiting the unprecedented resolutions obtained by combining visibilities from two telescopes in India and France, we showed that radio noise storms appear to have an internal fine structure with one or several bright and compact cores embedded in a more extended halo. We achieved resolutions of 31 arc sec at 327 MHz. The positions of cores fluctuates by less than their size over a few seconds. Their relative intensities may change over time of 2 s, implying that bursts originate from cores.

The minimum observed sizes of cores are of interest for discussing scatter broadening. At 327 MHz, we observed a compact storm with a remarkably stable size during the whole observation (1 h), with a minimum value of 31 arcsec, slightly smaller than those previously reported (40 arcsec). At 236 MHz, the smallest sizes we found (35 arcsec) correspond to the highest intensities of a particular core in a complex storm.

10. Radio Detection of a Rapid Disturbance launched by a Solar Flare.

Summary:

The study of moving disturbances in the solar atmosphere is an important topic for several reasons as uch disturbances may lead to shocks in the solar wind which have terrestrial consequences and because they may be studied in detail at relatively close range, they may reveal physical processes that are important but difficult to study in more distant astrophysical settings. A number of such disturbances are recognized. Some of the earliest detections were inferred from radio observations eg. beams of accelerated electrons freely streaming at 40,000  km s^-1 which produce type III radio bursts, coronal shocks at 500–2000 km s^-1 which produce type II radio bursts, and moving features at 200–1600 km s^-1 which produce moving type IV radio bursts.  In the chromosphere, “Moreton waves” are detected at velocities as high as 4000 km s^-1.

I have reported the direct observation of motion associated with a solar flare at a speed of 26,000 km s^-1. The motion  is seen from a radio source at 0.33 GHz, which suddenly starts moving during the flare. The disturbance itself does not seem to radiate, but it excites coronal features that continue to radiate after it passes. The inferred velocity is larger than any previously inferred velocity of a disturbance in the solar atmosphere apart from freely streaming beams of accelerated electrons.

Impact on the Field:

The observed motion of the source at a fixed frequency, low polarization, and moderate bandwidth are more consistent with the typical properties of moving type IV radio bursts than with classical coronal shock–associated type II bursts, but any disturbance at such a high velocity must be highly supersonic and should drive a shock. We speculate that the disturbance is associated with the realignment of magnetic fields connecting different portions of an active regions and is therefore important for space weather as it can drive shocks into the solar wind and impact the earths magnetosphere.

11. The Aditya Solarwind Particle Experiment (ASPEX) to be flown onboard the ADITYA-L1 Mission of ISRO in 2019:

Principal Investigator (PI): Janardhan, P.

Summary: 

• One of the most import features of the ASPEX experiment is that it will be able to identify the arrival time of ICMEs at L1 accurately by measuring the He⁺⁺/H⁺ number density ratios or helium abundance enhancements (HAE).  A He⁺⁺/H⁺ ratio greater than 0.08 is known to be the most reliable markers of CME arrival at 1 AU, ASPEX will thus be unique in its ability to predict Space Weather events caused by CME’s, a vital input for potentially harmful space weather events.

• The uniqueness of our experiment lies in the fact that Time resolved energy spectral measurements of both protons and alpha particles from the four directions will provide one the ability to address the anisotropy in the energy distribution of particles in the direction of the Parker spiral vis-a-vis other directions. This, in turn, will help to trace the origin of supra-thermal particles which could not be explained by only solar wind propagation.

ASPEX:

The ASPEX payload onboard the Aditya mission consists of two particle analyzers to take advantage of the unique location of the spacecraft at the L1 Lagrangian point of the Sun-Earth system to carry out systematic and continuous observations of particle fluxes over an energy range spanning 100 eV to 5 MeV. The payload consisting of two  components will cover the entire energy range – the Solar Wind Ion Spectrometer (SWIS) covering the low energy range (100 eV to 20 keV) using an electrostatic analyzer and the Suprathermal Energetic Particle Spectrometer (STEPS) covering the high energy range (20 keV to 5 MeV) using solid state detectors.

The primary focus of the ASPEX payload is to understand the solar and interplanetary processes (like shock effects, wave-particle interactions etc.) in the acceleration and energization of the solar wind particles. In order to achieve that it is necessary that ASPEX intends to measure low as well as high energy particles that are associated with slow and fast components of solar wind, suprathermal population, shocks associated with CME and CIR, and solar energetic particles (SEPs). Among these, it is expected that that the slow and fast components of the solar wind and some part of the suprathermal population can be measured in a predominantly radial direction. In addition, a part of the suprathermal population, CME and CIR-accelerated particles

and SEPs are expected to arrive at the detectors along the Parker spiral. The ratio He⁺⁺/H⁺ will be used as a compositional “flag” to differentiate (and identify) the arrivals of CME, CIR, SEP-related particles from those of the quiet solar wind origin.