Prof. Janardhan Padmanabhan, FNA Currivulum Vitaejerry/VITAE/Janardhan-Padmanabhan-CV-Homepage.pdf1. PhD Guide for Dr. Susanta Kumar Bisoi – 2008-2012 [PhD degree awarded in 2013

Prof. Janardhan Padmanabhan, FNA

- Currivulum Vitae –

Name

Date of Birth

Date of joining PRL

Marital Status

Present Designation

Address

Email

Mobile No

Educational Qualifications

Thesis Referee

Website

Janardhan Padmanabhan

15 February 1960

31 December 1993

Married

Senior Professor (H-Grade) and Dean, PRL

E-5 PRL Residences, Vikramnagar, Ahmedabad

[email protected]; [email protected]

(+91)9428246845

PhD in Physics – Gujarat Univ. - 1991

Prof. Antony Hewish, FRS, Nobel Laureate

https://www.prl.res.in/~jerry

http://www.flickr.com/photos/jerryprl

Employment details:

Position

Institution

Period

1. Senior Professor (H)

2. Senior Professor

3. Dean, PRL

4. Member Scientific

Advisory committee

5. Member 2.5m Telescope

Project Board

6. Chairman Academic

Committee

7. Member Post-Doctoral

Committee

8. Professor

Physical Research Laboratory

Physical Research Laboratory

Physical Research Laboratory

Physical Research Laboratory

Physical Research Laboratory

Physical Research Laboratory

Physical Research Laboratory

Physical Research Laboratory

01 Jul. 2019 - Present

01 Jan. 2016 – Jun. 2019

01 Dec. 2015 - Present

01 Dec 2015 – 31 Jan. 2017

2015 - 2016

01 Apr. 2013 – 31 Mar. 2015

01 Apr. 2012 – 31 Mar. 2014

01 Jan 2011 – 31 Dec 2015

9. Assoc. Professor

10. Reader

11. Scientist –SD

12. Post Doctoral Fellow

13. Post Doctoral Fellow

Physical Research Laboratory

Physical Research Laboratory

Physical Research Laboratory

National Centre for Radio

Astrophysics, NCRA, TIFR

Physical Research Laboratory

01 Jul. 2005 - 31 Dec 2010

01 Jan. 2001 – 30 Jun 2005

31 Dec. 1993 – 31 Dec. 2000

Dec. 1992 – Nov. 1993

Dec. 1991 – Nov. 1992

Experience/EmploymentAbroad:

1. Alexander Von Humboldt Research Fellow, Govt. of Germany (May 1996 − Dec.

1997)

RadioastronomischesInstitüt

Universität Bonn

Bonn, Germany.

2. Research Associate (August 1999 – October 2000)

Department of Astronomy

University of Maryland

College Park, USA

3. Visiting Professor (01 Sept. 2003 − 30 Nov. 2003)

Institute for Space-Earth Enviroment (ISEE)

Nagoya University, Japan.

4. Visiting Scientist (Feb. 2007 − Jan. 2008)

InstitutoNacional de Pesquisas (INPE)

Divisao de Astrofisica, Brazil.

5. Visiting Professor (Feb 2008)

Department of Applied Mathematics and Theoretical Physics,

Cambridge, UK

(2) Research Supervision (Guiding Ph.Ds/associated PDFs and other forms of interaction with

students/teachers from other organizations like summer trainees, PRL Associates etc.)

1. PhD Guide for Dr. Susanta Kumar Bisoi – 2008-2012 [PhD degree awarded in 2013

from MLSU, Udaipur].

2. PhD co-guide for Dr. V. Venkataraman – 2011-2015 [PhD degree awarded in 2015

from MLSU, Udaipur]

3. PhD guide for Dr. Priyanka Chaturvedi; co-guide Prof. Abhijit Chakraborty, PRL

(2010-2015) [PhD degree awarded in 2016 from MLSU, Udaipur].

4. PhD Guide for Mr. Rahul Kumar Kushwaha – Since 2015

(3) Current Professional Responsibilities

Senior Professor (H- Grade) and Dean, Physical Research Laboratory

(4) Details of research and Professional Accomplishments:

1. Member National Committee of COSPAR-URSI-SCOSTEP

2. Individual Member Union Radio-Scientifique Internationale (URSI)

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

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

5) Awards and Honours, Fellowships of Scientific Bodies

1. Elected in 2019 Fellow of the Indian National Science Academy, New Delhi

2. 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.

3. 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.

4. Awarded the Alexander Von Humboldt Research Fellowship in Astrophysics for the year

1996 by the Alexander Von Humboldt Foundation, Bonn, Germany.

5. 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

(6a) List of 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. 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.

34. 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.

35. 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.

36. 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:

37. 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.

38. 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.

39. Enigmatic solar wind disappearance events: Do we understand them?. Janardhan, P., (2006). Jou. Astrophys. Astron. 27, 1−7.

40. 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.

41. 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.

42. 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.

43. 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.

44. 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.

45. 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:

46. 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.

47. 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.

48. 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.

49. 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.

50. 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.

51. 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.

52. 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.

53. 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.

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

55. 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.

56. 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 – Present :

57. 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.

58. 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.

59. 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.

60. Amplitude of solar wind density turbulence from 10 Rs - 45 Rs 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.

61. 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.

62. 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.

63. 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.

64. 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.

65. 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 .

66. 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.

67. 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.

68. 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.

69. 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.

70. 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. [In Press].

71. 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.

72. 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,

https://doi.org/10.1007/s11207-019-1514-7.

73. 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.

74. 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, https://doi.org/10.1016/j.saa.2019.117393

75. 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, https://doi.org/10.1016/j.saa.2019.117797. Also appeared

on the cover page of ASTROPAH Newsletter as “Picture of the Month”

https://pubs.rsc.org/en/content/articlelanding/2020/CP/C9CP05440E#!divAbstract

Papers Published in Refereed Conference Proceedings:

76. 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.

77. Tracking Interplanetary Disturbances Using Interplanetary Scintillation. Janardhan, P., Balasubramanian, V. and Ananthakrishnan, S. (1997). Proc. 31st. ESLAB

Symp., ESA SP−415 , pp. 177−181.

78. 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

79. Radio Observations of Transient Solar Wind Flows. Balasubramanian, V., Janardhan, P., Srivatsan, R. and Ananthakrishnan, S. (1998). Proc.

of the 3rd. SOLTIP Symposium, pp. 319.

Eds. Feng, X.S., Wei, F.S., and Dryer, M.

80. 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.

81. 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

82. 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.

83. 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.

84. 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.

85. 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.

86. 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.

87. 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

D. Banerjee, J. Jiang, K. Kusano & S. Solanki, eds.

(6b) Books/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.

(7) Invited Talks at International and National Conferences (separately with paper number in

chronological order):

1. Estimation of Solar Wind Velocity From the Three-Station IPS Observatory - India.

Janardhan, P.

(Invited Talk - Published in the Proc. of the Indo-U.S. Workshop on IPS and Solar

Activity - Feb. 1988, pp. 83).

2. 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).

3. 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).

4. 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).

5. 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).

6. 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).

7. 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).

8. 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).

9. 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).

10. 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).

11. 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).

12. 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).

13. 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. ).

14. The Deepest Solar Minimum in 100 Years: Earliest Inner Heliospheric Signatures

Janardhan, P.

(Invited Talk -Presented at the Symposium on Physics of the Solar Transition Region and

Corona IUCAA, Pune, Sept. 4−7 2011 ).

15. 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 ).

16. 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)

17. 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.‖

18. 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.

19. Are we on the verge of a Maunder –Like Grand Solar Minimum

Janardhan, P.

(Invited Colloquium - - MPIFR – Bonn, 26 June 2015)

20. 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. Note: Presentation Made by Prof. S. Ananthakrishnan as I

could not attend the meeting)

21. 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).

22. 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)

(8) Organisation of Conferences/Summer Schools, etc.

I. 2nd URSI Regional Conference on Radio Science 2015 (URSI-RCRS 2015) New Delhi,

India, from 16 to 19 November 2015.

II. APRASC- 2019: URSI Asia-Pacific Radio Science Conference (AP-RASC 2019 ) New

Delhi, India from 09 – 15 March, 2019.

(9) Outreach Activities:

I. Give talks each year at local schools and colleges

(10) Contributions to and participation in the general management aspects of the Laboratory:

1. Have been a member of several PRL committees. Have been the chairman of the A&A

Division at PRL and Chairman of the PRL, Academic Committee.

(11) National and International scientific collaborations:

Have active Collaborations with Cambridge, UK; ISEE Japan; NAO Beijing;

NCRA, TIFR, India

(12) Any additional information:

1. PI of the ASPEX Payload onboard India’s first dedicated solar mission (ADITYA-L1) to

the L1 Lagrangian point of the Sun-Earth system.

2. Recent Work on Ducting Emission Reported as a Science Nugget in Community of

European Solar Radio Astronomers (CESRA)

http://www.astro.gla.ac.uk/users/eduard/cesra/?p=1960

3. An article on our work was featured in Times of India entitled ― Sunspots point to

Looming Little Ice Age.

https://www.prl.res.in/prl-eng/documents/prl_in_news/April06-2016.pdf

4. An Article Entitled - A New Angle on the Effects of Solar Wind on a novel method of

detecting geoeffective CIR was Published in Nature India - doi:10.1038/nindia.2017.116

Published online – Nature India, 7 September 2017

5. Our Recent work on Decimetric Emission far away from a flaring site was reported as a

CESRA Science Nugget.

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

2018

https://www.natureasia.com/en/nindia/article/10.1038/nindia.2018.153

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.

Some important contributions have been highlighted and briefly described

below:

I. 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 6o

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.

II. 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 nominee's 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 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.

The nominees 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 (≥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. 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, 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, 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.

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 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.

III. 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 by the nominee 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.

IV. 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.

V. 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.

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

Important findings:

The nominee has carried out extensive IPS observations, with the Ooty Radio Telescope

(ORT) 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.

VII. 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.

VIII. Decimetric emission 500 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.

IX. 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.

X. 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.

XI. 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 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.