Solar, Solar Wind and Solar Radio Studies :
My research covers a wide range of interests from radio studies of the sun and the solarwind,
with emphasis on "Space Weather" studies using observations of Interplanetary Scintillation (IPS)
and meter wavelength solar imaging observations. Aditionally, I have an interest in studies
of solar photospheric magnetic fields, radio observations of comets, experimental studies of
astrochemical ices, shock processing of molecules, and exo-planets. Over the past decade I have
been involved in scentific payload development for solar studies and led the development, as
Principal Investigator (PI), of the Aditya
Solarwind
Particle
Experiment
(ASPEX) payload onboard India's first
observatory-class Mission ADITYA-L1 to study the sun from the L1 Lagrangian Point of
the sun-earth system. ADITYA-L1 was launched on on 02 September 2023.
In recent times, I have been 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.
Awards:
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Chandrayaan-2 CLASS and XSM payload teams
were awarded the ASI Zubin-Kembhavi Award
in 2024 for Observational and Instrumentation work in Astronomy. The award,instituted by
the Astronomical Society of India (ASI), and given annually, carries a cash prize of one lakh
rupees and a plaque.
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Was elected as a Fellow of the
Indian National Science Academy (INSA) in 2019.
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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.
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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.
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Awarded the Alexander Von Humboldt Research Fellowship
in Astrophysics for the year 1996 by the Alexander Von Humboldt Foundation, Bonn, Germany.
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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.
International Collaborations:
A Study of rms Electron Density Fluctuations in Cometary Ion Tails - In collaboration with the Australia
Telescope National Facility, Australia.
Detection of Ammonia and Water in Comet Hale-Bopp - In collaboration with the Radioastronomisches
Institute, Bonn, Germany.
Coronal Velocity Measurements using the Ulysses Spacecraft - In collaboration with the
Radioastronomisches Institute, Bonn, Germany.
A Study of the acceleration Regime of the Solar Wind using Ulysses - In collaboration with the
Radioastronomisches Institute, Bonn, Germany.
Detection of Extremely High Velocity Disturbances Launched by Solar Flares using the VLA - In
collaboration with the University of Maryland, USA.
A Study of Solar Wind Disappearance Events - In collaboration with the Solar Terrestrial
Environmental Laboratory, Nagoya University, Japan.
Understanding the Cause of Very Low Density Solar Wind Flows at 1 AU - In
collaboration with the University of Cambridge, UK.
Callibrating the Brazillian Decametric Array using GPS Signals - In collaboration with the
Institute for Space Physics (Instituto Nacional de PesquisasEspaciais, INPE), Brazil.
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.
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.
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Popular Articles and News Reports:
- An article on our work was featured in Times
of India entitled “ Sunspots point to Looming Little Ice Age.
Times of India - April 2016
- 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
- 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.
- 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
- An article on our work was featured in Times
of India entitled “ The Suns Magnetic field is weakening"
Times of India - October 2019
- 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.
- 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.
- 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.
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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.
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 was launched in 02 September 2023. The payoad was designed,
developed and built at PRL with an aim to study particle energetics and anisotropies in the
energy range 100 eV to 5 MeV.
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Selected Publications:
Some selected publications are listed below.
Publications from years 2015 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- The Structure of Solar Radio Noise Storms.
C. Mercier, Prasad Subramanian, G. Chambe,
Janardhan, P., (2015).
A&A. 576, A136
- 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.
- 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,
doi: 10.1002/2017GL073038.
- Solar Cycle 24: An Unusual Polar Field Reversal
Janardhan, P., Fujiki, K., Ingale, M.,
Susanta Kumar Bisoi and Diptiranjan Rout (2018).
A&A 618, A148.
- 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
- Another Mini Solar Maximum in the Offing: A Prediction
for the Amplitude of Solar Cycle 25
Susanta Kumar Bisoi., Janardhan, P.
and Ananthakrishnan, S. (2020).
JGR,
125,
DOI:2019JA027508.
- 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
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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.
- 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.
- 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. (2022).
MNRAS, 517, 4845 – 4855,
DOI:10.1093/mnras/stac2637
- N-Graphene Synthesized in Astrochemical Ices
Shivaraman, B, 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 ,
and, Mason N J (2023).
European Physical Journal-D
77, 24, DOI:10.1140/epjd/s10053-023-00590-z
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Ultraviolet spectrum reveals the presence of ozone on Juipeter's moon Callisto
R Ramachandran, J K Meka, K K Rahul, W Khan, J-I Lo, B-M Cheng, D V Mifsud, B N Rajasekhar,
A Das, H Hill, Janardhan, P
., Anil Bhardwaj, N J Mason, B Sivaraman (2024).
Icarus
DOI: 10.1016/j.icarus.2023.115896
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