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Curriculum Vitae
Name
JANARDHAN PADMANABHAN
Date of Birth
15 February 1960
Nationality
INDIAN
Spouse Name
Mrs. SHOBHA JANARDHAN
Address for
Correspondence
(in Block Letters)
PROF. JANARDHAN PADMANABHAN
DEAN, PHYSICAL RESEARCH LABORATORY
NAVRANGPURA
AHMEDABAD – 380 009
INDIA
Email : [email protected]
Phone : (+91)79 26314861 (Off.); (+91) 79 26860261 (Res.)
Mobile :(+91) 9428246845
Permanent Address:
PROF. JANARDHAN PADMANABHAN
E-5 PRL RESIDENCES,
VIKRAMNAGAR
AMBLI-BOPAL ROAD
AHMEDABAD – 380 058
INDIA
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Educational qualifications
Exam Passed
Board
Year of
Passing
Subject
Pre-Degree Exam
Bangalore Univ.
1979
Physics, Chemistry, Maths &
Biology
B.Sc. Degree
Bangalore Univ.
1982
Physics, Chemistry and
Mathematics
MSc. Degree
Univ. of Hyderabad
1984
Physics,
PhD
Physical Research
Laboratory/ Gujarat
Univ.
1991
PHYSICS
Thesis referee:
Prof. Antony Hewish,
Nobel Laureate, FRS,
Cavendish Laboratory
Univ. of Cambridge, UK.
Details of previous/present employment :
Name of Employer
Post held
Period
From To
Physical Research Laboratory
Senior Professor
01 January 2016
Present
Physical Research Laboratory
Dean, and member
Scientific Advisory
committee, PRL.
01 December 2015
Present
Physical Research Laboratory
Member 2.5m Telescope
Project Board
22 December 2015
Present
Physical Research Laboratory
Chairman Academic
Committee
01 April 2013
31 March 2015
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Physical Research Laboratory
Member Post-Doctoral
Committee
01 April 2012
30 March 2014
Physical Research Laboratory
Professor
01 January 2011
31 December
.2015
Physical Research Laboratory
Associate Professor
01 July 2005
31 December
2010
Physical
Research Laboratory
Reader
01 January
2001
30 June 2005
Physical Research Laboratory
Scientist -D
31 December 1993
31 December
2000
National Centre for Radio
Astrophysics (NCRA,TIFR),
India
Post Doctoral Fellow
December 1992
30 December
1993
Physical Research Laboratory
Post-Doctoral Fellow
December 1991
November
1992
Awards:
1. 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.
2. 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.
3. Awarded the Alexander Von Humboldt Research Fellowship in Astrophysics for
the year 1996 by the Alexander Von Humboldt Foundation, Bonn, Germany.
4. 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.
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PhD Thesis Supervision:
Guide:
1. 2008 -2012 Dr. Susanta Kumar Bisoi (PhD awarded in 2013 from MLSU,
Udaipur).
Co-Guide
2. 2011- 2015 Dr. V. Venkataraman (PhD awarded in 2015 from MLSU, Udaipur)
3. 2010- 2015 Dr. Priyanka Chaturvedi (PhD awarded in 2016 from MLSU,
Udaipur)
Supervision of Post-doctoral Fellows:
I have supervised and mentored 4 post-doctoral fellows. Currently I am supervising
three post-doctoral fellows.
Research Collaborations:
1. Solar wind, Solar imaging and Solar Heliospheric Studies using IPS – In
collaboration with TIFR, and NCRA, India.
2. A Study of rms Electron Density Fluctuations in Cometary Ion Tails – In
collaboration with the Australia Telescope National Facility, Australia.
3. Detection of Ammonia and Water in Comet Hale-Bopp – in collaboration with the
Radioastronomisches Institute, Bonn, Germany.
4. Coronal Velocity Measurements using the Ulysses Spacecraft - in collaboration
with the Radioastronomisches Institute, Bonn, Germany.
5. A Study of the acceleration Regime of the Solar Wind using Ulysses - in
collaboration with the Radioastronomisches Institute, Bonn, Germany.
6. Detection of Extremely High Velocity Disturbances Launched by Solar Flares
using the VLA – in collaboration with the University of Maryland, USA.
7. A Study of Solar Wind Disappearance Events - in collaboration with the Solar
Terrestrial Environmental Laboratory, Nagoya University, Japan.
8. Understanding the Cause of Very Low Density Solar Wind Flows at 1 AU - in
collaboration with the University of Cambridge, UK.
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9. Callibrating the Brazillian Decametric Array using GPS Signals - in collaboration
with the Institute for Space Physics (Instituto Nacional de PesquisasEspaciais, INPE),
Brazil.
10. 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.
11. 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.
Research Experience outside India:
May 1996 − Dec. 1997
Alexander Von Humboldt Research Fellow,
Govt. of Germany
RadioastronomischesInstitüt
Universität Bonn
Bonn, Germany.
Aug. 1999 − Oct. 2000
Research Associate
Department of Astronomy
University of Maryland
College Park, USA.
01 Sept. 2003 − 30 Nov. 2003
Visiting Professor
Institute for Space-Earth Enviroment (ISEE)
Nagoya University, Japan.
Feb. 2007 − Jan. 2008
Visiting Scientist
InstitutoNacional de Pesquisas (INPE)
Divisao de Astrofisica
Brazil.
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Administrative experience:
1. Dean PRL and member Scientific Advisory Committee – 01 December 2015 to
Present.
2. Project Board Member for the new 2.5 m IR and Optical Telescope– 22 December
2015 to Present.
3. Chairman Academic Committee, PRL – April 2013 to March 2015.
4. Member Post-Doctoral Committee, PRL – April 2012 to March 2014.
5. Member National Committee of COSPAR-URSI-SCOSTEP 2013 to present
Recent Research Interests and Important Scientific
Contributions:
Solar and Heliospheric Related Studies
A Systematic, long term study of declining solar
photospheric magnetic fields: inner-heliospheric signatures
and possible implications
Papers resulting from this study – 2010 onwards.
1. 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.
2. The Prelude to the Deep Minimum between Solar Cycles 23 and 24:
Interplanetary Scintillation Signatures in the Inner Heliosphere by Janardhan,
P., Susanta Kumar Bisoi, Ananthakrishnan, S., Tokumaru, M., Fujiki, K.,
(2011). Geophys. Res. Lett., 38, L20108, doi:10.1029/2011GL049227.
3. Peculiar behaviour 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.
4. 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.
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5. 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.
6. 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.
7. 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
8. 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. Guest Editor: Janardhan,
P.)
Introduction
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 reveals periods like the
Maunder minimum (1645—1715) when the sunspot activity was extremely low or virtually
non-existent. Using 14
C 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.
Our recent studies of 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 (≥45ο) 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.
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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 Solar-Terrestrial Environment Laboratory
(STEL), 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, ЄN ≡ ∆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, we have re-examined solar photospheric magnetic fields between 1975—
2013, the HMF between 1975—2014, and the solar wind micro-turbulence levels between
1983—2013. We estimated the peak sunspot number of solar cycle 25, and address 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
examine how the recent changes in solar activity have influenced the near-Earth space
environment. We therefore also 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.
From our study, based on analysis of past 39 years of solar and interplanetary observations
covering solar cycles 21-24, we conclude that
1. Both solar photospheric fields and solar wind micro-turbulence levels have been
steadily declining from ~1995 and that the trend is likely to continue at least until the
minimum of cycle 24 in 2020.
2. The HMF, 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.
3. 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.
Another study however, based on the expected behaviour of the axial dipole moment after
polar reversal in Cycle 24, reported that Cycle 25 will be similar to Cycle 24. There are
studies that show that the peak sunspot number prior to the onset of the Maunder minimum
was around 50. Our study, the decline in both the high-latitude fields and the micro
turbulence levels in the inner-heliosphere since 1995, which among themselves shows a great
deal of similarity in their steadily declining trends, thus begs the question as to whether we
are headed towards a Maunder-like grand minimum beyond Cycle 25?
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
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activity will be significantly decreased leading us to another prolonged sunspot minimum
lasting several decades. Our study on the other hand, using an entirely different approach,
also suggests a long period of reduced solar activity.
Modelling 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 14
C 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 our analysis suggests a similar weak cycle 25.
All these indicate that a grand minimum akin to a Maunder like minimum may be in
progress.
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. However, our observations of a
significant correlation between the night time F2-region electron density and sunspot number
show no such declining trend for the former. This indicates that even in the impending solar
quiet phase when there will be little/no sunspots, the reduced F-region electron density will,
being in phase with solar activity (solar EUV radiation), give rise to a reduced ionospheric
reflection cut-off frequency. In general, a reduced sunspot count will have no adverse effect
on ionospheric processes including large scale atmospheric current systems.
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. Currently the lowest observing
frequencies in India are 40 MHz for solar studies and 150 MHz extra-galactic studies. Our
results 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.
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Probing the Inner Scale of the Turbulent Spectrum in the Solar
Wind.
Papers resulting from this study –
1. 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.
2. Amplitude of solar wind density turbulence from 10–45 R
K. Sasikumar Raja, Madhusudan Ingale, R. Ramesh, Prasad Subramanian, P. K.,
Manoharan and P. Janardhan. (2016). Jou. Geophys. Res. [In Press].
Introduction:
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.
Results:
If the length scales probed by the IPS technique are larger than the inner scale, we can
conclude that the density fluctuations discussed in this paper lie in the inertial range of the
turbulent spectrum. We showed that this is the case all the way from the Sun to the Earth only
if the inner scale is the electron gyroradius, or if it is due to proton cyclotron resonance, and
the density is given by the fourfold Newkirk model.
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Combining Visibilities from two Separate Radio Telescopes to
Achieve Extremely High Resolution, High Dynamic Range Solar
Images:
Papers resulting from this study –
1. The Structure of Solar Radio Noise Storms by C. Mercier, Prasad Subramanian, G.
Chambe, Janardhan, P., (2015). A&A. 576, A136.
2. 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.
Introduction:
Solar activity in the past 50 years has been generally high with as many as half of the 10 most
intense solar cycles on record having occurred in this period. However, as stated earlier, we
are currently experiencing an extremely prolonged and deep solar minimum, with the sun
being at its quietest in almost a century. This is therefore a unique time and opportunity to
pursue studies of the quiet sun.
Radio emission from the sun can be of both thermal and non-thermal origin. Thermal
emission is not localized and can reveal structures having a wide spectrum of scales, which
evolves on time scales of hours or days, and the synthesis technique is optimal for imaging
these structures. Non-thermal emission is mainly confined to compact bursts, often brighter
than the quiet sun by orders of magnitude, the short duration of which requires snapshot
imaging. In both cases, the ability to choose the observing frequency would allow one to
probe the corona at different heights (increasing with decreasing frequency) above the base of
the corona. The range 1000-100 MHz corresponds roughly to the range between the base of
the corona up to a few tens of solar radii, depending on the local density in the coronal
structures at those heights.
On the other hand, the propagation of radio waves in the corona is affected by the scattering
due to inhomogeneities in the coronal electron density which produces a lower limit for the
apparent size of compact coronal radio sources. However, it has been shown that the
apparently low brightness temperature of the solar corona at metric and decametric
wavelengths could be due to a low filling factor in the sources of radiation. Either way, high
resolution observations additionally provide us with an important diagnostic to probe the
turbulence level in the corona.
Advantages of Joint Observations.
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The GMRT and the NRH have complementary capabilities. The NRH is a dedicated solar
instrument operating at 10 frequencies between 150 and 450 MHz. It is a 'T' shaped array of
48 antennas, with baselines from 50 to 3200 m. The resulting uv coverage is dense near the
origin, allowing fields of view large enough for imaging the whole radio sun. The resolution
however is at best ~1 minute of arc, depending on frequency. On the other hand the GMRT
has longer baselines (up to 26 km), giving very high resolution, but the relative lack of
shorter baselines prevents one from imaging a wide source such as the sun without aliasing,
especially above 200 MHz. Systematic joint GMRT-NRH quiet sun observations that
combine the capabilities of a wide field of view and of high spatial resolution are therefore
expected to yield very high dynamic range (> 1000) maps which could give interesting new
insights and results. It may be noted that synthesis maps produced earlier using the VLA
have dynamic ranges of a few hundred at best. High dynamic range images of the quiet sun
will be crucial in unveiling faint non-thermal sources that could potentially contribute to
coronal heating.
We used all available joint GMRT/NRH observations of noise storms from 2002 to 2006.
Joint observations are possible over ∼08:30–12:00 UT. The storm on Aug. 27, 2007, already
presented by us earlier in a 2006 publication, was used again since we improved the data
processing. The NRH uses an integration time τ = 0.125 s, shorter than typical burst
durations, whereas the GMRT uses a longer τ of 2.1 or 17 s. The NRH data were integrated
over the time intervals used by the GMRT. The final time cadence was thus that of the
GMRT. The time profiles of bursts are therefore smoothed and their maximum intensity
might be underestimated.
Results:
We have shown that combining visibilities from the NRH and GMRT works well and is
useful, providing snapshot images with a high dynamical range, a wide field of view, and a
high spatial resolution. These characteristics were essential in the present study since noise
storms show internal structure and since several storms often coexist. Even with the few
cases studied here, we get new insights on the structure of noise storms. It was already known
that the electron density in noise storm sources exceeds that in the ambient corona. We
specified over density factors of 5–25 relatively to the widely accepted Saito’s model, and
even more relatively to quiet corona models derived from purely radio observations. From
multi-frequency NRH observations, we derived the scale height of the electron density in
noise storm sources and showed that it is smaller than in the ambient corona. This implies
that the coronal regions emitting at different frequencies do not lie along the same magnetic
flux tube. This questions the classical columnar model and also the current theories for
emission mechanism, which imply magnetic trapping of supra-thermal electrons of a few
KeV. Noise storms appear to have an internal fine structure with one or several bright and
compact cores embedded in a more extended halo. The positions of the cores fluctuate 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. It follows that the overall apparent shape and size
of storms may change rapidly, giving the impression of being quasi-random. The sense of
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circular polarization is the same over the whole storm. The polarization rate is stable for each
core, but may differ between the 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. It is presently difficult to conclude
whether these apparent sizes are real or broadened by scattering, considering that the
predictions of current theories are limited by the poor present knowledge of the turbulence
level and of its space and time variations. In addition, there are too few reliable observations
with high spatial resolution. More observations of storms at various solar longitudes could be
helpful. However, conclusive observations of storms at several simultaneous frequencies with
high spatial resolution (<10 arcsec) and time resolution (<1s), in order to observe the same
storm at different levels and to clearly separate bursts and continuum, does not appear
feasible with currently operating instruments.
Non-Solar Related Radio Studies:
A Systematic Search for High Redshift Radio Galaxies at
150 MHz.
Papers resulting from this study –
1. 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.
Introduction
It has been nearly 15 years since the discovery of the highest redshift radio galaxy at a
redshift of 5.19, though close to 50 radio galaxies are known beyond redshift of 3. Most of
them were discovered using the empirical correlation that the high-redshift radio galaxies
(HzRG) tend to exhibit steep radio spectra. A large number of HzRG’s are yet to be
discovered which are 10 to 100 times less luminous than the known HzRG’s. The 150 MHz
band of GMRT(Giant Metrewave Radio Telescope, India, http://www.ncra.tifr.res.in) with its
large field of view(3 degrees), high angular resolution (~20 arc sec)and better sensitivity (~1
mJy from a full synthesis observation) is well suited fill this large gap, by searching for steep
spectrum sources using deep radio observations. It has now been well established that HzRG
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exhibit steep radio spectra, and hence ultra-steep spectrum radio sources provide good
candidates for high-redshift radio galaxies. Nearly all of the high redshift radio galaxies have
been found using this relation. We have started a programme with the Giant Meterwave
Radio Telescope (GMRT) to exploit this correlation at flux density levels of about 10 to 100
times deeper than the known HzRG.
Using GMRT observations at 150 MHz, we have obtained deep, high resolution radio
observations at 150 MHz with for several ’deep’ fields which are well studied at higher radio
frequencies and in optical, with an aim to detect candidate high redshift radio galaxies. From
correlating these radio sources with respect to the high-frequency catalogues such as FIRST
and NVSS at 1.4 GHz, and optical catalogues such as SDSS and DEEP2, we have found a list
of steep spectrum (spectral index, alpha > 1) radio sources which remain undetected in SDSS
and DEEP2 optical images. These are good candidates for high redshift radio galaxies and
will be followed up with large optical telescopes.
Results
Thee of the fields from DEEP2 survey (Newman et al. 2012), centred at 1652+3455,
2330+0000and 0230+0000 were observed at 150 MHz with the Giant Metrewave Radio
Telescope (GMRT)using a bandwidth of 16 MHz. The data from the first field was unusable
due to heavy RFI. The analysis of the remaining two fields were done using both, the
standard AIPS procedures and using an automated pipeline. The images produced by the pipe
line yielded relatively better rms and hence used in this work. The rms for the field
2330+0000 is 1.2mJy/beam with a resolution of 20× 17 arcsec while for the field 0230+0000
it is 1.2 mJy/beam, with a resolution of 21 × 17 arcsec. The combined catalogue of both the
DEEP2 fields have ~1100 sources down to flux density of 10 mJy. The median flux density
of the sample is 55 mJy.
We cross matched the 150 MHz sources with the VLA FIRST survey (Becker et al. 1995).
About 65% sources have counterparts in NVSS and FIRST. Spectral index was computed
using the flux densities at 150 MHz and using the 1400 MHz flux density from NVSS. The
median spectral index is 0.79. To have a sample of steep spectrum sources, we have adopted
the spectral index cut off of 1. We find about 150 radio sources with spectral index steeper
than 1. In order to cross match with SDSS, we have first cross matched the 150 MHz source
with the VLA FIRST Survey. Wherever counterparts were found, the VLA FIRST position
was used to search for counterparts in SDSS. Among sources with SDSS counterparts, 16.9%
have spectral index steeper than 1. Among sources without SDSS counterparts, 26.0% have
spectral index steeper than 1, the increased fraction of steep spectrum sources without optical
counterparts is as expected in the redshift-spectral index correction. K-band imaging is aimed
for sources unidentified in SDSS, to obtain redshift estimate using the K-z relation.
Spectroscopic determination of redshift for sources with redshift estimate > 3 is required
thereafter.
We also came across an unresolved source at 150 MHz, which shows clear FRII morphology
in FIRST. The counterpart for this source is not detected in SDSS. Using the FRI and FRII
break luminosity and observed radio flux density, its redshift is estimated to be > 2.
15 | P a g e
Discovery of a Rare Radio Galaxy and New Insights into
AGN Activity as Revealed by its Jets
Papers resulting from this study –
1. J1216+0709 : A Radio Galaxy with Three Episodes of AGN Jet Activity
Veeresh Singh, Ishwara-Chandra, C.H., PreetiKharb, Shweta Srivastava Janardhan,
P., (2016). ApJ , 826, 132-137.,doi:10.3847/0004-637X/826/2/132.
Introduction:
Most radio galaxies exhibit a single pair of radio lobes marking the endpoints of their jets.
But the unusual three pairs of radio lobes of a recently observed radio galaxy may reveal
information about this galaxy’s past. Radio galaxies, a subclass of active galactic nuclei
(AGN), typically exhibit what’s known as a ―core-jet-lobe‖ structure. A super-massive black
hole accreting matter at the galaxy’s core flings material out at the poles, forming two
symmetric jets of highly energetic particles. These jets can travel vast distances before
spreading out into giant, radio-emitting lobes.
Thousands of these double-lobed radio galaxies have been observed, but a few dozen are
unique cases that exhibit two pairs of lobes. These different pairs likely formed during two
different phases of AGN activity: the jets were activated long enough to inflate the first lobes,
then turned off, and then turned back on again and inflated the second lobes. Now, the third-
ever case of a triple set of lobes has been discovered: the radio galaxy J1216+0709, located
roughly 2 billion light-years away.
Results:
J1216+0709 is an early-type elliptical galaxy hosting a supermassive black hole of several
billion solar masses at its core. The galaxy’s unusual radio structure was discovered using
India’s Giant Metrewave Radio Telescope (GMRT). The radio lobes detected in J1216+0709
consist of an inner pair ~310 thousand light-years across, a nearly coaxial middle pair ~770
thousand light-years across, and an outer pair ~2.7 million light-years across. Several
important observations about the galaxy’s morphology are:
1. The outer pair of lobes is much fainter than the inner pairs, and it doesn’t contain any
hot spots. This makes sense if the outer lobes are the oldest, as expected, and are no
longer being actively fed.
2. The inner pairs of lobes are both brighter and longer on their eastern sides than on
their western sides, suggesting that the jets are intrinsically asymmetric.
3. The outer pair of lobes is bent with respect to the inner jets. This could mean that the
material is interacting with the surrounding environment, which may have a large-
scale density gradient. Alternatively, it could mean that the galaxy moved in between
the two cycles of AGN activity.
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We find that the host galaxy is part of a small group of three galaxies. Though there’s no
visible disturbance in the host galaxy’s morphology, minor interactions with two nearby
dwarf galaxies could be triggering the sporadic AGN activity. In the future, more sensitive
optical data may be able to confirm this model.
Approved Space Mission Proposal:
1. The Aditya Solarwind Particle Experiment (ASPEX) to be
flown onboard the ADITYA-L1 Mission of ISRO in 2019:
Principal Investigator (PI) : Janardhan, P.
PRL has proposed an experiment onboard the Aditya mission consisting of two particle
analysers 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 analyser 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 of PRL on-board the ADITYA-L1 satellite 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
He++/H+ ratio 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.
Therefore, it is necessary that the measurements are planned suitably so that all the science
objectives are fulfilled. The major science objectives of the ASPEX payload is as follows.
Can we get insights into the generation mechanism(s) of supra-thermal and other
energetic ions in the interplanetary space?
How are these ions associated with the solar processes?
Can the particles associated with interplanetary shock (associated with CME, CIR
etc.) processes be identified and the shock related processes be addressed?
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Does anisotropy in the energy distribution of particles exist in the direction of the
Parker spiral vis-à-vis other directions?
How does the He++
/H+ number density ratio change corresponding to various solar
events (Flares, CME’s, CIR’s) and what is the range of values of this ratio.
What is physical mechanism responsible for the increase of the He++
/H+ number
density ratio?
Last but not the least, what is the importance of the above-mentioned processes for
the impact on the near-earth space weather?
Addressing the above mentioned issues require systematic observations of particle fluxes at
selected ranges as well as He++
/H+ number density ratio from the L1 point. Keeping this in
mind, the Aditya Solar wind Particle Experiment (ASPEX) payload consisting of SWIS and
STEPS instruments, is proposed. SWIS will have the capability to measure solar wind
particles in the energy range of 100 eV to 20 keV in the plane of the ecliptic and normal to
the plane of the ecliptic. One of the SWIS units will receive and differentiate (H+ and He
++
ions) particles (species differentiation mode) from the ecliptic plane whereas another SWIS
unit will measure the total flux irrespective of species (species integration mode) from across
the ecliptic plane. STEPS, on the other hand, will measure the particle flux in the 20 keV - 5
MeV energy range in the sunward, antisunward, Parker and ecliptic north and south
directions. Three (Sunward, Parker, Antisunward) STEPS units will be designed to operate in
the species differentiation mode whereas the remaining three (intermediate between sunward
and Parker, ecliptic north and South) STEPS unit will operate in species-integrated mode.
A significant amount of work has been carried out since 2013. Both the SWIS and STEPS
packages are being developed at PRL. The proof of concept of the SWIS- Top Hat Analyzer
has been demonstrated and the back end instrumentation is being developed by a team of
several scientists and engineers at PRL.
Refereed Research Publications (2010 to present):
Papers Related to Solar and Heliospheric Studies:
1. 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.
2. 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.
3. The Prelude to the Deep Minimum between Solar Cycles 23 and 24:
Interplanetary Scintillation Signatures in the Inner Heliosphere
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Janardhan, P., Susanta Kumar Bisoi, Ananthakrishnan, S., Tokumaru, M., Fujiki, K.,
(2011). Geophys. Res. Lett., 38, L20108, doi:10.1029/2011GL049227.
4. 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.
5. 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.
6. 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, S.
Ananthakrishnan, Tokumaru, M., and Fujiki,
K. (2014). AtrophysicalJournal 795, 69−76.
7. 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.
8. The Structure of Solar Radio Noise Storms. C. Mercier, Prasad Subramanian, G. Chambe, Janardhan,P., (2015). A&A. 576, A136
9. 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.
10. 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.
11. 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.
12. Amplitude of solar wind density turbulence from 10–45 R
Sasikumar Raja, Madhusudan Ingale, R. Ramesh, Prasad Subramanian, P. K.,
Manoharan and P. Janardhan. (2016). Jou. Geophys. Res. [In Press].
19 | P a g e
Papers Related to General Astronomy (Non-Solar and Heliospheric
Studies):
13. 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.
14. 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.
15. Determination of mass and orbital parameters of a low-mass star HD 213597B
Priyanka Chaturvedi1, Rohit Deshpande, Vaibhav Dixit, Arpita Roy Abhijit
Chakraborty, SuvrathMahadevan, B.G. Anandarao, Leslie Hebb and P.
Janardhan (2014). MNRAS 442, 3737−3744.
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 , 826, 132-137.,doi:10.3847/0004-637X/826/2/132.
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 , 826, doi:10.3847/0004-637X/826/1/27.
18. Multi-wavelength study of the star-formation in the S237 HII Region
Dewangan, L.K., Ojha, D.K., Zinchenko, Janardhan,P. and Luna, A. (2016). ApJ [In
Press].
19. 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 [In Press].
Refereed Publications in Peer Reviewed Conference Proceedings
[2010 – onwards]:
1. Peculiar behaviour 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.
2. Asymmetry in the periodicities of solar photospheric fields: A probe to the
unusual solar minimum prior to cycle 24
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Susanta Kumar Bisoi, Janardhan,P., (2013). Proc. IAU Symp.
294, 8, 85−86 DOI: 10.1017/S1743921313002305.
3. 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.
4. 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.
5. Decline in solar polar magnetic fields and heliospheric micro-turbulence levels:
Are we headed towards a Maunder minimum? Susanta Kumar Bisoi, Janardhan,P., and Ananthakrishnan, S. (2014). Proc. Of the
XXX1 General Assembly and Scientific Symposium (URSI GASS). pp 1- 4.
6. 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. Vadawalea, P. Janardhan, D. Chakrabartya, A. R. Srinivas, P. Shuklab,
P. Kumara, K. P. Subramaniana, B. Bapat, and P. R. Adhyarua (2016). Proc. Of SPIE
Vol. 9905, doi: 10.1117/12.2232259.
Membership to Professional Bodies:
1. Member National Committee of COSPAR-URSI-SCOSTEP
2. Member of the International Astronomical Union (IAU).
3. Member of the American Geophysical Union (AGU).
Full List of Peer Reviewed Research Publications:
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). ActaAstronautica, 21, No. 3, 189−196.
21 | P a g e
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.
22 | P a g e
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 .andAnanthakrishnan, 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.
19. 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 160th
IAU Colloquium− ASP Conf. Series., pp.
477−448. Eds. S. Johnston, M.A. Walker and M. Bailes.
20. 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.
21. 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.
22. 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.
23. Tracking Interplanetary Disturbances Using Interplanetary Scintillation. Janardhan, P., Balasubramanian, V. and Ananthakrishnan, S. (1997). Proc. 31st.
ESLAB Symp., ESA SP−415 , pp. 177−181.
24. 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.
25. 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.
26. 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.
27. Radio Observations of Transient Solar Wind Flows. Balasubramanian, V., Janardhan, P., Srivatsan, R. and Ananthakrishnan, S.
23 | P a g e
(1998). Proc. of the 3rd. SOLTIP Symposium, pp. 319.
Eds. Feng, X.S., Wei, F.S., and Dryer, M.
28. 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.
29. 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.
30. 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
31. 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.
32. 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.
33. 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). AnnalesGeophysica, 18, 1003.
34. H−alpha Observations of Be Stars. Banerjee, D.P.K., Rawat, S.D. and Janardhan, P. (2000). A&A Suppl., 147, 229.
35. 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.
36. 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.
37. 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.
38. 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.
24 | P a g e
39. 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.
40. 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.
41. 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.
42. 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.
43. 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.
44. 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.
45. Enigmatic solar wind disappearance events: Do we understand them? Janardhan, P., (2006). Jou. Astrophys. Astron. 27, 1−7.
46. 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
47. 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.
48. 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.
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49. 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.
50. 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.
51. 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.
52. 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.
53. 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.
54. 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.
55. 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.
56. Peculiar behaviuor 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.
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.
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.
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.
26 | P a g e
60. 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.
61. 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.
62. Determination of mass and orbital parameters of a low-mass star HD 213597B
Priyanka Chaturvedi1, Rohit Deshpande, Vaibhav Dixit, Arpita Roy Abhijit
Chakraborty, SuvrathMahadevan, B.G. Anandarao, Leslie Hebb and P.
Janardhan (2014). MNRAS 442,3737−3744, DOI: 10.1093/mnras/stul127.
63. 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.
64. 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.
65. The Structure of Solar Radio Noise Storms. C. Mercier, Prasad Subramanian, G. Chambe, Janardhan,
P., (2015). A&A. 576, A136
66. 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.
67. 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, No2, 147-156.
68. 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.
69. J1216+0709 : A Radio Galaxy with Three Episodes of AGN Jet Activity
Veeresh Singh, Ishwara-Chandra, C.H., PreetiKharb, Shweta Srivastava Janardhan,
P., (2016). ApJ , 826, 132-137.,doi:10.3847/0004-637X/826/2/132.
70. Star formation activity in the neighbourhood of WR 1503-160L star in the mid-
infrared bubble N46
27 | P a g e
Dewangan, L.K., Baug, T., Ojha, D.K.,Janardhan,P. Ninan, J. P., Luna, A. and
Zinchenko, I. (2016). ApJ , 826, doi:10.3847/0004-637X/826/1/27.
71. 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, A. R. Srinivas, P.
Shuklab, P. Kumara, K. P.Subramaniana, B. Bapat, and P. R. Adhyarua (2016). Proc.
of SPIE Vol. 9905, doi: 10.1117/12.2232259.
72. Amplitude of solar wind density turbulence from 10–45 R
K. Sasikumar Raja, Madhusudan Ingale, R. Ramesh, Prasad Subramanian, P. K.,
Manoharan and P. Janardhan. (2016). Jou. Geophys. Res. [In Press].
73. Multi-wavelength study of the star-formation in the S237 HII Region
Dewangan, L.K., Ojha, D.K., Zinchenko, Janardhan,P. and Luna, A. (2016). ApJ
[In Press].
74. 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 [In Press].
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