Astronomy & Astrophysics Division
Physical Research Laboratory
Ahmedabad - 380 009
INDIA.


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Janardhan Padmanabhan


Janardhan Padmanabhan



Phone:   (+91) 79 2631 4505, 4610 (O);
              (+91) 79 2686 0261 (R);

e-mail :    jerry AT prl.res.in 


Summary of Research Interests:

Solar, Solar Wind and Solar Radio Studies :

My current research interests are centered around studies of the Solar Wind and Space Physics with emphasis on "Space Weather" studies using observations of Interplanetary Scintillation (IPS). In recent times, I have been actively persuing a detailed study of solar magnetic fields and solar wind micro-turbulence levels. Both of these have been steadily decreasing from around the early to mid nineties. Our studies strongly suggests that we are probably headed for another Maunder like solar minimum beyond solar cycle 25. I have also been involved in Solar Radio Astronomical studies via meter wavelength solar imaging observations carried out using a new technique of combining visibilities from the Giant Meterwave Radiotelescope (GMRT) facility at NCRA,TIFR, Pune and the Nancay Radio Heliograph in France.

International Collaborations:



<sun>   A Study of rms Electron Density Fluctuations in Cometary Ion Tails - In collaboration with the Australia Telescope National Facility, Australia.

<sun>   Detection of Ammonia and Water in Comet Hale-Bopp - In collaboration with the Radioastronomisches Institute, Bonn, Germany.

<sun>   Coronal Velocity Measurements using the Ulysses Spacecraft - In collaboration with the Radioastronomisches Institute, Bonn, Germany.

<sun>   A Study of the acceleration Regime of the Solar Wind using Ulysses - In collaboration with the Radioastronomisches Institute, Bonn, Germany.

<sun>   Detection of Extremely High Velocity Disturbances Launched by Solar Flares using the VLA - In collaboration with the University of Maryland, USA.

<sun>   A Study of Solar Wind Disappearance Events - In collaboration with the Solar Terrestrial Environmental Laboratory, Nagoya University, Japan.

<sun>   Understanding the Cause of Very Low Density Solar Wind Flows at 1 AU - In collaboration with the University of Cambridge, UK.

<sun>   Callibrating the Brazillian Decametric Array using GPS Signals - In collaboration with the Institute for Space Physics (Instituto Nacional de PesquisasEspaciais, INPE), Brazil.

<sun>   A Study of Solar Magnetic Fields over the Past three Solar Cycles - In collaboration with the Institute Space-Earth Environment (ISEE), Research, Nagoya University, Japan.

<sun>   High Dynamic Range and High Resolution Solar Imaging Studies using the Giant Meterwave Radio Telescope and The Nancay Radio Heliograph - In collaboration with the Observatoire de Paris, France.




Further details on my earlier research interests and on studies carried out successfully and bulletted below can be obtained fron the "Research Interests" link in the left hand column at the top of this page.

<sun>   IPS studies of the Solar Wind and Interplanetary Medium

<sun>   IPS studies of the Solar Wind at High Latitudes.

<sun>   VLA Imaging of Solar Flares and Compact Radio Sources.

<sun>   Solar Imaging Observations with the Giant Meterwave Radio Telescope (GMRT).

<sun>   IPS studies of Interstellar Scattering.

<sun>   IPS and Emission Line studies of Cometary Ion Tails and Coma.

<sun>   Very Long Baseline Interferometric (VLBI) Studies at 327 MHz.

<sun>   Studies of H-alpha Emission Line profiles of Be Stars.



Future Plans:


In recent times, I have been actively persuing a detailed study of solar magnetic fields and solar wind micro-turbulence levels. Both of these have been steadily decreasing from around the early to mid nineties. Our studies strongly suggests that we are probably headed for another Maunder like solar minimum beyond solar cycle 25. I have also been working on combining visibilities obtained from the GMRT and the Nancay Radio Heliograph in France which have yielded solar images with extraordinary dynamic range. This method therefore provides one the possibility of studying faint features that occur along with bright energetic phenomena on the solar disk like flares and CME's and is being actively followed up. I am the PI for a payload onboard the ADITYA-L1 mission to study the Sun. At PRL we are developing a payload, the Aditya Solar wind Particle EXperiment to study particle energetics and anisotropies in the energy range 100 eV to 5 MeV.

Selected Publications:


Some selected publications are listed below. Publications from years 2011 onwards can be accessed via the "Recent Publications" link in the left hand column at the top of this page and similarly, a complete list of publications in refereed journals including IAU circulars published can be accessed via the "All Publications" link at the top of the page.

  1. 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.

  2. 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.

  3. 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.

  4. Radio Detection of a Rapid Disturbance Launched by a Solar Flare.
    White, S.M., Janardhan, P . and Kundu, M.R. (2000). ApJL., 533, L167.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. The Structure of Solar Radio Noise Storms.
    C. Mercier, Prasad Subramanian, G. Chambe, Janardhan, P., (2015).  A&A. 576, A136

  13. 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.

  14. 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.

  15. 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.  [In Press]

  16. 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  [In Press]

  17. 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  [In Press]