Research Interests
Space weather
Cometary plasma dynamics and Solar wind interaction
Earth's radiation belts
Geomagnetic storms and substorms
Solar wind-Magnetosphere-Ionosphere coupling
Auroral activity
Ionospheric irregularity
Ionosphere modeling
Positions
2023 December - present: Specially Appointed Professor (特任教授): University of Science of Technology of China (USTC), P. R. China
2023 January - 2023 November: CAS Distinguished Researcher: University of Science of Technology of China (USTC), P. R. China
2019 November - 2022 November: Ramanujan Fellow: Indian Institute of Technology Indore (IITI), India
2018 November - 2019 October: Ramanujan Fellow: National Atmospheric Research Laboratory (NARL), India
2016 March - 2018 October: Postdoctoral Fellow: Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Centre National de la Recherche Scientifique (CNRS), Orléans, France
2012 August - 2015 September: Postdoctoral Fellow: Divisão de Geofísica Espacial (DGE), Instituto Nacional de Pesquisas Espaciais (INPE), São Paulo, Brazil
Education
PhD (Space Physics): University of Calcutta 2012
MSc (Physics): University of Calcutta 2005
BSc (Physics): University of Calcutta 2003
Publications
81. Despirak, I., P. Setsko, A. Lubchich, R. Hajra, Y. Sakharov, G. Lakhina, V. Selivanov, B. T. Tsurutani (2024), Geomagnetically induced currents (GICs) during strong geomagnetic activity (storms, substorms, and magnetic pulsations) on 23–24 April 2023, Journal of Atmospheric and Solar-Terrestrial Physics, 261, 106293, https://doi.org/10.1016/j.jastp.2024.106293.
80. Tsurutani, B. T., A. Sen, R. Hajra, G. S. Lakhina, R. B. Horne, and T. Hada (2024), Review of the August 1972 and March 1989 (Allen) Space Weather Events: Can We Learn Anything New From Them?, Journal of Geophysical Research: Space Physics, 129, e2024JA032622, https://doi.org/10.1029/2024JA032622.
79. Zhou, X., X. Gao, Q. Lu, R. Hajra, Y. Ke, R. Chen, and J. Ma (2024), Prompt disappearance of magnetospheric chorus waves caused by high-speed magnetosheath jets, Journal of Geophysical Research: Space Physics, 129, e2024JA032576, https://doi.org/10.1029/2024JA032576.
78. Hajra, R., B. T. Tsurutani, Q. Lu, G. S. Lakhina, A. Du, E. Echer, A. M. S. Franco, M. J. A. Bolzan, and X. Gao (2024), Ultra-relativistic Electron Acceleration during High-Intensity Long-Duration Continuous Auroral Electrojet (AE) Activity (HILDCAA) Events, The Astrophysical Journal, 965: 146, https://doi.org/10.3847/1538-4357/ad2dfe.
77. Jones, G. H., C. Snodgrass, C. Tubiana, M. Küppers, H. Kawakita, L. M. Lara, J. Agarwal, N. André, N. Attree, U. Auster, S. Bagnulo, M. Bannister, A. Beth, N. Bowles, A. Coates, L. Colangeli, C. C. van Damme, V. Da Deppo, J. De Keyser, V. Della Corte, N. Edberg, M. R. El-Maarry, S. Faggi, M. Fulle, R. Funase, M. Galand, C. Goetz, O. Groussin, A. Guilbert-Lepoutre, P. Henri, S. Kasahara, A. Kereszturi, M. Kidger, M. Knight, R. Kokotanekova, I. Kolmasova, K. Kossacki, E. Kührt, Y. Kwon, F. La Forgia, A.-C. Levasseur-Regourd, M. Lippi, A. Longobardo, R. Marschall, M. Morawski, O. Muñoz, A. Näsilä, H. Nilsson, C. Opitom, M. Pajusalu, A. Pommerol, L. Prech, N. Rando, F. Ratti, H. Rothkaehl, A. Rotundi, M. Rubin, N. Sakatani, J. P. Sánchez, C. S. Wedlund, A. Stankov, N. Thomas, I. Toth, G. Villanueva, J.-B. Vincent, M. Volwerk, P. Wurz, A. Wielders, K. Yoshioka, K. Aleksiejuk, F. Alvarez, C. Amoros, S. Aslam, B. Atamaniuk, J. Baran, T. Barciński, T. Beck, T. Behnke, M. Berglund, I. Bertini, M. Bieda, P. Binczyk, M.-D. Busch, A. Cacovean, M. T. Capria, C. Carr, J. M. C. Marín, M. Ceriotti, P. Chioetto, A. Chuchra-Konrad, L. Cocola, F. Colin, C. Crews, V. Cripps, E. Cupido, A. Dassatti, B. J. R. Davidsson, T. De Roche, J. Deca, S. Del Togno, F. Dhooghe, K. D. Hanna, A. Eriksson, A. Fedorov, E. Fernández-Valenzuela, S. Ferretti, J. Floriot, F. Frassetto, J. Fredriksson, P. Garnier, D. Gaweł, V. Génot, T. Gerber, K.-H. Glassmeier, M. Granvik, B. Grison, H. Gunell, T. Hachemi, C. Hagen, R. Hajra, Y. Harada, J. Hasiba, N. Haslebacher, M. L. H. De La Revilla, D. Hestroffer, T. Hewagama, C. Holt, S. Hviid, I. Iakubivskyi, L. Inno, P. Irwin, S. Ivanovski, J. Jansky, I. Jernej, H. Jeszenszky, J. Jimenéz, L. Jorda, M. Kama, S. Kameda, M. S. P. Kelley, K. Klepacki, T. Kohout, H. Kojima, T. Kowalski, M. Kuwabara, M. Ladno, G. Laky, H. Lammer, R. Lan, B. Lavraud, M. Lazzarin, O. Le Duff, Q.-M. Lee, C. Lesniak, Z. Lewis, Z.-Y. Lin, T. Lister, S. Lowry, W. Magnes, J. Markkanen, I. M. Navajas, Z. Martins, A. Matsuoka, B. Matyjasiak, C. Mazelle, E. M. Epifani, M. Meier, H. Michaelis, M. Micheli, A. Migliorini, A.-L. Millet, F. Moreno, S. Mottola, B. Moutounaick, K. Muinonen, D. R. Müller, G. Murakami, N. Murata, K. Myszka, S. Nakajima, Z. Nemeth, A. Nikolajev, S. Nordera, D. Ohlsson, A. Olesk, H. Ottacher, N. Ozaki, C. Oziol, M. Patel, A. S. Paul, A. Penttilä, C. Pernechele, J. Peterson, E. Petraglio, A. M. Piccirillo, F. Plaschke, S. Polak, F. Postberg, H. Proosa, S. Protopapa, W. Puccio, S. Ranvier, S. Raymond, I. Richter, M. Rieder, R. Rigamonti, I. R. Rodriguez, O. Santolik, T. Sasaki, R. Schrödter, K. Shirley, A. Slavinskis, B. Sodor, J. Soucek, P. Stephenson, L. Stöckli, P. Szewczyk, G. Troznai, L. Uhlir, N. Usami, A. Valavanoglou, J. Vaverka, W. Wang, X.-D. Wang, G. Wattieaux, M. Wieser, S. Wolf, H. Yano, I. Yoshikawa, V. Zakharov, T. Zawistowski, P. Zuppella, G. Rinaldi, and H. Ji (2024), The Comet Interceptor Mission, Space Science Reviews, 220: 9, https://doi.org/10.1007/s11214-023-01035-0.
76. Guo, J., S. Lu, Q. Lu, J. A. Slavin, W. Sun, J. Ren, X. Wang, Y. Lin, R. Hajra, and R. Wang (2023), Three-Dimensional Global Hybrid Simulations of Mercury's Disappearing Dayside Magnetosphere, Journal of Geophysical Research: Planets, 128, e2023JE008032, https://doi.org/10.1029/2023JE008032.
75. Hajra, R., B. T. Tsurutani, Q. Lu, L. Shan, A. Du, R. Wang, S. Lu, and X. Gao (2023), Extreme Rarefaction of Solar Wind: A Study on Origin and Characteristics using Ulysses Observations, The Astrophysical Journal, 955: 120, https://doi.org/10.3847/1538-4357/acf45c.
74. Tsurutani, B. T., G. P. Zank, V. J. Sterken, K. Shibata, T. Nagai, A. J. Mannucci, D. M. Malaspina, G. S. Lakhina, S. G. Kanekal, K. Hosokawa, R. B. Horne, R. Hajra, K. H. Glassmeier, C. T. Gaunt, P. F. Chen, and S. I. Akasofu (2023), Space Plasma Physics: A Review, IEEE Transactions on Plasma Science, 51, 1595-1655, https://doi.org/10.1109/TPS.2022.3208906.
73. Hajra, R., B. T. Tsurutani, G. S. Lakhina, Q. Lu, A. Du, and L. Shan (2023), Interplanetary Shocks between 0.3 and 1.0 au: Helios 1 and 2 Observations, The Astrophysical Journal, 951: 75, https://doi.org/10.3847/1538-4357/acd370.
72. Hajra, R., E. Echer, A. M. S. Franco, and M. J. A. Bolzan (2023), Earth’s magnetotail variability during supersubstorms (SSSs): A study on solar wind–magnetosphere–ionosphere coupling, Advances in Space Research, 72, 1208-1223, https://doi.org/10.1016/j.asr.2023.04.013.
71. Tsurutani, B. T., G. S. Lakhina, and R. Hajra (2023), Comments on “New Insights From the 2003 Halloween Storm Into the Colaba 1600 nT Magnetic Depression During the 1859 Carrington Storm” by S. Ohtani (2022), Journal of Geophysical Research: Space Physics, 128, e2022JA031034, https://doi.org/10.1029/2022JA031034.
70. Echer, E., A. Lucas, R. Hajra, A. M. S. Franco, M. J. A. Bolzan, and L. E. S. Nascimento (2023), Geomagnetic Activity Following Interplanetary Shocks in Solar Cycles 23 and 24, Brazilian Journal of Physics, 53: 79, https://doi.org/10.1007/s13538-023-01294-w.
69. Hajra, R. (2023), Near-Earth High-Speed and Slow Solar Winds: A Statistical Study on Their Characteristics and Geomagnetic Impacts, Solar Physics, 298: 53, https://doi.org/10.1007/s11207-023-02141-6.
68. Tsurutani, B. T., and R. Hajra (2023), Energetics of Shock Triggered Supersubstorms (SML < -2500 nT), The Astrophysical Journal, 946: 17, https://doi.org/10.3847/1538-4357/acb143.
67. Echer, E., A. M. S. Franco, F. P. Magalhães, M. J. A. Bolzan, and R. Hajra (2023), Study of Neptune dayside magnetosheath fluctuations during Voyager-2 flyby, Advances in Space Research, 71, 3468-3478, https://doi.org/10.1016/j.asr.2022.12.022.
66. Sunny, J. V., A. G. Nair, M. Babu, and R. Hajra (2023), A Comparative Study on Geoeffective and Non-geoeffective Corotating Interaction Regions, Advances in Space Research, 71, 268-274, https://doi.org/10.1016/j.asr.2022.09.051.
65. Echer, E., A. M. S. Franco, E. C. Junior, R. Hajra, and M. J. A. Bolzan (2022), Solar-Wind High-Speed Stream (HSS) Alfvén Wave Fluctuations at High Heliospheric Latitudes: Ulysses Observations During Two Solar-Cycle Minima, Solar Physics, 297: 143, https://doi.org/10.1007/s11207-022-02070-w.
64. Tsurutani, B. T., and R. Hajra (2022), Extremely Slow (Vsw < 300 km s−1) Solar Winds (ESSWs) at 1 au: Causes of Extreme Geomagnetic Quiet at Earth, The Astrophysical Journal, 936: 155, https://doi.org/10.3847/1538-4357/ac7444.
63. Chen, R., B. T. Tsurutani, X. Gao, Q. Lu, H. Chen, G. S. Lakhina, and R. Hajra (2022), The Structure and Microstructure of Rising-tone Chorus with Frequencies Crossing at f ∼ 0.5 fce, Journal of Geophysical Research: Space Physics, 127, e2022JA030438, https://doi.org/10.1029/2022JA030438.
62. Hajra, R., J. V. Sunny, M. Babu, and A. G. Nair (2022), Interplanetary Sheaths and Corotating Interaction Regions: A Comparative Statistical Study on Their Characteristics and Geoeffectiveness, Solar Physics, 297: 97, https://doi.org/10.1007/s11207-022-02020-6.
61. Bolzan, M. J. A., E. Echer, A. M. S. Franco, and R. Hajra (2022), Identification of the planetary magnetosphere boundaries with the wavelet multi-resolution analysis, Journal of Atmospheric and Solar-Terrestrial Physics, 230, 105842, https://doi.org/10.1016/j.jastp.2022.105842.
60. Hajra, R., and J. V. Sunny (2022), Corotating Interaction Regions during Solar Cycle 24: A Study on Characteristics and Geoeffectiveness, Solar Physics, 297: 30, https://doi.org/10.1007/s11207-022-01962-1.
59. Hajra, R., and B. T. Tsurutani (2022), Near-Earth Sub-Alfvénic Solar Winds: Interplanetary Origins and Geomagnetic Impacts, The Astrophysical Journal, 926: 135, https://doi.org/10.3847/1538-4357/ac4471.
58. Goetz, C., H. Gunell, M. Volwerk, A. Beth, A. Eriksson, M. Galand, P. Henri, H. Nilsson, C. S. Wedlund, M. Alho, L. Andersson, N. Andre, J. De Keyser, J. Deca, Y. Ge, K.-H. Glassmeier, R. Hajra, T. Karlsson, S. Kasahara, I. Kolmasova, K. LLera, H. Madanian, I. Mann, C. Mazelle, E. Odelstad, F. Plaschke, M. Rubin, B. Sanchez-Cano, C. Snodgrass, and E. Vigren (2022), Cometary plasma science: Open science questions for future space missions, Experimental Astronomy, 54, 1129-1167, https://doi.org/10.1007/s10686-021-09783-z.
57. Hajra, R. (2022), Intense Geomagnetically Induced Currents (GICs): Association with Solar and Geomagnetic Activities, Solar Physics, 297: 14, https://doi.org/10.1007/s11207-021-01945-8.
56. Hajra, R. (2022), Intense, long-duration geomagnetically induced currents (GICs) caused by intense substorm clusters, Space Weather, 20, e2021SW002937, https://doi.org/10.1029/2021SW002937.
55. Franco, A. M. S., R. Hajra, E. Echer, and M. J. A. Bolzan (2021), Seasonal features of geomagnetic activity: a study on the solar activity dependence, Annales Geophysicae, 39, 929-943, https://doi.org/10.5194/angeo-39-929-2021.
54. Hajra, R. (2021), Variation of the interplanetary shocks in the inner heliosphere, The Astrophysical Journal, 917: 91, https://doi.org/10.3847/1538-4357/ac0897.
53. Tsurutani, B. T., and R. Hajra (2021), The Interplanetary and Magnetospheric causes of Geomagnetically Induced Currents (GICs) > 10 A in the Mäntsälä Finland Pipeline: 1999 through 2019 – Erratum, Journal of Space Weather and Space Climate, 11, 32, https://doi.org/10.1051/swsc/2021015.
52. Hajra, R., A. M. de Souza Franco, E. Echer, and M. J. A. Bolzan (2021), Long‐Term Variations of the Geomagnetic Activity: A Comparison Between the Strong and Weak Solar Activity Cycles and Implications for the Space Climate, Journal of Geophysical Research: Space Physics, 126, e2020JA028695, https://doi.org/10.1029/2020JA028695.
51. Tsurutani, B. T., and R. Hajra (2021), The Interplanetary and Magnetospheric causes of Geomagnetically Induced Currents (GICs) > 10 A in the Mäntsälä Finland Pipeline: 1999 through 2019, Journal of Space Weather and Space Climate, 11, 23, https://doi.org/10.1051/swsc/2021001.
50. Hajra, R. (2021), September 2017 Space-Weather Events: A Study on Magnetic Reconnection and Geoeffectiveness, Solar Physics, 296: 50, https://doi.org/10.1007/s11207-021-01803-7.
49. Hajra, R. (2021), Seasonal dependence of the Earth’s radiation belt – new insights, Annales Geophysicae, 39, 181-187, https://doi.org/10.5194/angeo-39-181-2021.
48. Hajra, R. (2021), Weakest Solar Cycle of the Space Age: A Study on Solar Wind-Magnetosphere Energy Coupling and Geomagnetic Activity, Solar Physics, 296: 33, https://doi.org/10.1007/s11207-021-01774-9.
47. Tsurutani, B. T., R. Chen, X. Gao, Q. Lu, J. S. Pickett, G. S. Lakhina, A. Sen, R. Hajra, S. A. Park, and B. J. Falkowski (2020), Lower-Band “Monochromatic” Chorus Riser Subelement/Wave Packet Observations, Journal of Geophysical Research: Space Physics, 125, e2020JA028090, https://doi.org/10.1029/2020JA028090.
46. Hajra, R., B. T. Tsurutani, and G. S. Lakhina (2020), The Complex Space Weather Events of 2017 September, The Astrophysical Journal, 899: 3, https://doi.org/10.3847/1538-4357/aba2c5.
45. Nemeth, Z., A. Timar, K. Szego, P. Henri, R. Hajra, and G. Wattieaux (2020), Plasma distribution around comet 67P in the last month of the Rosetta Mission, Icarus, 350, 113924, https://doi.org/10.1016/j.icarus.2020.113924.
44. Hajra, R., P. Henri, X. Vallières, M. Galand, M. Rubin, B. T. Tsurutani, N. Gilet, L. Bucciantini, and Z. Nemeth (2020), Ionospheric total electron content of comet 67P/Churyumov-Gerasimenko, Astronomy & Astrophysics, 635, A51, https://doi.org/10.1051/0004-6361/201937022.
43. Tsurutani, B. T., G. S. Lakhina, and R. Hajra (2020), The physics of space weather/solar-terrestrial physics (STP): what we know now and what the current and future challenges are, Nonlinear Processes in Geophysics, 27, 75-119, https://doi.org/10.5194/npg-27-75-2020.
42. Tsurutani, B. T., S. A. Park, B. J. Falkowski, J. Bortnik, G. S. Lakhina, A. Sen, J. S. Pickett, R. Hajra, M. Parrot, and P. Henri (2019), Low Frequency (f < 200 Hz) Polar Plasmaspheric Hiss: Coherent and Intense, Journal of Geophysical Research: Space Physics, 124, 10063-10084, https://doi.org/10.1029/2019JA027102.
41. Tsurutani, B. T., R. Hajra, E. Echer, and G. S. Lakhina (2019), Comment on “First Observation of Mesosphere Response to the Solar Wind High‐Speed Streams” by W. Yi et al., Journal of Geophysical Research: Space Physics, 124, 8165-8168, https://doi.org/10.1029/2018JA026447.
40. Breuillard, H., P. Henri, L. Bucciantini, M. Volwerk, T. Karlsson, A. Eriksson, F. Johansson, E. Odelstad, I. Richter, C. Goetz, X. Vallières, and R. Hajra (2019), The properties of the singing comet waves in the 67P/Churyumov-Gerasimenko plasma environment as observed by the Rosetta mission, Astronomy & Astrophysics, 630, A39, https://doi.org/10.1051/0004-6361/201834876.
39. Edberg, N. J. T., F. L. Johansson, A. I. Eriksson, D. J. Andrews, R. Hajra, P. Henri, C. Simon Wedlund, M. Alho, and E. Thiemann (2019), Solar flares observed by Rosetta at comet 67P/Churyumov-Gerasimenko, Astronomy & Astrophysics, 630, A49, https://doi.org/10.1051/0004-6361/201834834.
38. Tsurutani, B. T., S. A. Park, B. J. Falkowski, G. S. Lakhina, J. S. Pickett, J. Bortnik, G. Hospodarsky, O. Santolik, M. Parrot, P. Henri, and R. Hajra (2018), Plasmaspheric hiss: coherent and intense, Journal of Geophysical Research: Space Physics, 123, 10009-10029, https://doi.org/10.1029/2018JA025975.
37. Hajra, R., P. Henri, M. Myllys, K. L. Héritier, M. Galand, C. Simon Wedlund, H. Breuillard, E. Behar, N. J. T. Edberg, C. Goetz, H. Nilsson, A. I. Eriksson, R. Goldstein, B. T. Tsurutani, J. Moré, X. Vallières, and G. Wattieaux (2018), Cometary plasma response to interplanetary corotating interaction regions during 2016 June – September: a quantitative study by the Rosetta Plasma Consortium, Monthly Notices of the Royal Astronomical Society, 480, 4544-4556, https://doi.org/10.1093/mnras/sty2166.
36. Heritier, K. L., M. Galand, P. Henri, F. L. Johansson, A. Beth, A. I. Eriksson, X. Vallières, K. Altwegg, J. L. Burch, C. Carr, E. Ducrot, R. Hajra, and M. Rubin (2018), Plasma source and loss at comet 67P during the Rosetta mission, Astronomy & Astrophysics, 618, A77, https://doi.org/10.1051/0004-6361/201832881.
35. Hajra, R., and B. T. Tsurutani (2018), Interplanetary shocks inducing magnetospheric supersubstorms (SML < -2500 nT): unusual auroral morphologies and energy flow, The Astrophysical Journal, 858: 123, https://doi.org/10.3847/1538-4357/aabaed.
34. Engelhardt, I. A. D., A. I. Eriksson, G. Stenberg Wieser, C. Goetz, M. Rubin, P. Henri, H. Nilsson, E. Odelstad, R. Hajra, and X. Vallières (2018), Plasma density structures at comet 67P/Churyumov-Gerasimenko, Monthly Notices of the Royal Astronomical Society, 477, 1296-1307, https://doi.org/10.1093/mnras/sty765.
33. Hajra, R., P. Henri, X. Vallières, J. More, N. Gilet, G. Wattieaux, C. Goetz, I. Richter, B. T. Tsurutani, H. Gunell, H. Nilsson, A. I. Eriksson, Z. Nemeth, J. L. Burch, and M. Rubin ( 2018), Dynamic unmagnetized plasma in the diamagnetic cavity around comet 67P/Churyumov-Gerasimenko, Monthly Notices of the Royal Astronomical Society, 475, 4140-4147, https://doi.org/10.1093/mnras/sty094.
32. Tsurutani, B. T., G. S. Lakhina, E. Echer, R. Hajra, C. Nayak, A. J. Mannucci, and X. Meng (2018), Comment on “Modeling extreme “Carrington-type” space weather events using three-dimensional global MHD simulations” by C.M. Ngwira, A. Pulkkinen, M.M. Kuznetsova and A. Glocer, Journal of Geophysical Research: Space Physics, 123, 1388-1392, https://doi.org/10.1002/2017JA024779.
31. Souza, A. M., E. Echer, M. J. A. Bolzan, and R. Hajra (2018), Cross-correlation and cross-wavelet analyses of the solar wind IMF Bz and auroral electrojet index AE coupling during HILDCAAs, Annales Geophysicae, 36, 205-211, https://doi.org/10.5194/angeo-36-205-2018.
30. Guarnieri, F. L., B. T. Tsurutani, L. E. A. Vieira, R. Hajra, E. Echer, A. J. Mannucci, and W. D. Gonzalez (2018), A correlation study regarding the AE index and ACE solar wind data for Alfvénic intervals using wavelet decomposition and reconstruction, Nonlinear Processes in Geophysics, 25, 67-76, https://doi.org/10.5194/npg-25-67-2018.
29. Hajra, R., B. T. Tsurutani, C. G. M. Brum, and E. Echer (2017), High-speed solar wind stream effects on the topside ionosphere over Arecibo: A case study during solar minimum, Geophysical Research Letters, 44, 7607-7617, https://doi.org/10.1002/2017GL073805.
28. Hajra, R., P. Henri, X. Vallières, M. Galand, K. Héritier, A. I. Eriksson, E. Odelstad, N. J. T. Edberg, J. L. Burch, T. Broiles, R. Goldstein, K. H. Glassmeier, I. Richter, C. Goetz, B. T. Tsurutani, H. Nilsson, K. Altwegg, and M. Rubin (2017), Impact of a cometary outburst on its ionosphere – Rosetta Plasma Consortium observations of the outburst exhibited by comet 67P/Churyumov-Gerasimenko on 19 February 2016, Astronomy & Astrophysics, 607, A34, https://doi.org/10.1051/0004-6361/201730591.
27. Henri, P., X. Vallières, R. Hajra, C. Goetz, I. Richter, K.-H. Glassmeier, M. Galand, M. Rubin, A. I. Eriksson, Z. Nemeth, E. Vigren, A. Beth, J. L. Burch, C. Carr, H. Nilsson, B. T. Tsurutani, and G. Wattieaux (2017), Diamagnetic region(s): structure of the unmagnetised plasma around comet 67P/CG, Monthly Notices of the Royal Astronomical Society, 469, S372-S379, https://doi.org/10.1093/mnras/stx1540.
26. Mendes, O., M. O. Domingues, E. Echer, R. Hajra, and V. E. Menconi (2017), Characterization of high-intensity, long-duration continuous auroral activity (HILDCAA) events using recurrence quantification analysis, Nonlinear Processes in Geophysics, 24, 407-417, https://doi.org/10.5194/npg-24-407-2017.
25. Souza, A. M., E. Echer, M. J. A. Bolzan, and R. Hajra (2016), A study on the main periodicities in interplanetary magnetic field Bz component and geomagnetic AE index during HILDCAA events using wavelet analysis, Journal of Atmospheric and Solar-Terrestrial Physics, 149, 81-86, https://doi.org/10.1016/j.jastp.2016.09.006.
24. Tsurutani, B. T., R. Hajra, T. Tanimori, A. Takada, R. Bhanu, A. J. Mannucci, G. S. Lakhina, J. U. Kozyra, K. Shiokawa, L. C. Lee, E. Echer, R. V. Reddy, and W. D. Gonzalez (2016), Heliospheric plasma sheet (HPS) impingement onto the magnetosphere as a cause of relativistic electron dropouts (REDs) via coherent EMIC wave scattering with possible consequences for climate change mechanisms, Journal of Geophysical Research: Space Physics, 121, 10130-10156, https://doi.org/10.1002/2016JA022499.
23. Hajra, R., B. T. Tsurutani, E. Echer, W. D. Gonzalez, and J. W. Gjerloev (2016), Supersubstorms (SML < -2500 nT): magnetic storm and solar cycle dependences, Journal of Geophysical Research: Space Physics, 121, 7805-7816, https://doi.org/10.1002/2015JA021835.
22. Hajra, R., S. K. Chakraborty, B. T. Tsurutani, A. DasGupta, E. Echer, C. G. M. Brum, W. D. Gonzalez, and J. H. A. Sobral (2016), An empirical model of ionospheric total electron content (TEC) near the crest of the equatorial ionization anomaly (EIA), Journal of Space Weather and Space Climate, 6, A29, https://doi.org/10.1051/swsc/2016023.
21. Da Silva, L. A., P. Satyamurty, L. R. Alves, V. M. Souza, P. R. Jauer, M. V. D. Silveira, M. S. Echer, R. Hajra, C. Medeiros, J. P. Marchezi, M. Rockenbach, N. R. Rigozo, C. M. Denardini, O. Mendes Jr., A. Dal Lago, and L. E. A. Vieira (2016), Comparison of geophysical patterns in the southern hemisphere mid-latitude region, Advances in Space Research, 58, 2090-2103, https://doi.org/10.1016/j.asr.2016.04.003.
20. Verkhoglyadova, O. P., X. Meng, A. J. Mannucci, B. T. Tsurutani, L. A. Hunt, M. G. Mlynczak, R. Hajra, and B. A. Emery (2016), Estimation of energy budget of ionosphere-thermosphere system during two CIR-HSS events: observations and modeling, Journal of Space Weather and Space Climate, 6, A20, https://doi.org/10.1051/swsc/2016013.
19. Remya, B., B. T. Tsurutani, R. V. Reddy, G. S. Lakhina, and R. Hajra (2015), Electromagnetic cyclotron waves in the dayside subsolar outer magnetosphere generated by enhanced solar wind pressure: EMIC wave coherency, Journal of Geophysical Research: Space Physics, 120, 7536-7551, https://doi.org/10.1002/2015JA021327.
18. Hajra, R., B. T. Tsurutani, E. Echer, W. D. Gonzalez, C. G. M. Brum, and L. E. A. Vieira, and O. Santolik (2015), Relativistic electron acceleration during HILDCAA events: are precursor CIR magnetic storms important?, Earth, Planets and Space, 67, 109, https://doi.org/10.1186/s40623-015-0280-5.
17. Tsurutani, B. T., R. Hajra, E. Echer, and J. W. Gjerloev (2015), Extremely intense (SML ≤ -2500 nT) substorms: isolated events that are externally triggered?, Annales Geophysicae Communicates, 33, 519-524, https://doi.org/10.5194/angeo-33-519-2015.
16. Mannucci, A. J., O. P. Verkhoglyadova, B. T. Tsurutani, X. Meng, X. Pi, C. Wang, G. Rosen, E. Lynch, S. Sharma, A. Ridley, W. Manchester, B. Van Der Holst, E. Echer, and R. Hajra (2015), Medium-range thermosphere-ionosphere storm forecasts, Space Weather, 13, 125-129, https://doi.org/10.1002/2014SW001125.
15. Hajra, R., B. T. Tsurutani, E. Echer, W. D. Gonzalez, and O. Santolik (2015), Relativistic (E > 0.6, > 2.0 and > 4.0 MeV) electron acceleration at geosynchronous orbit during high-intensity long-duration continuous AE activity (HILDCAA) events, The Astrophysical Journal, 799: 39, https://doi.org/10.1088/0004-637X/799/1/39.
14. Hajra, R., E. Echer, B. T. Tsurutani, and W. D. Gonzalez (2014), Superposed epoch analyses of HILDCAAs and their interplanetary drivers: solar cycle and seasonal dependences, Journal of Atmospheric and Solar-Terrestrial Physics, 121, 24-31, https://doi.org/10.1016/j.jastp.2014.09.012.
13. Hajra, R., B. T. Tsurutani, E. Echer, and W. D. Gonzalez (2014), Relativistic electron acceleration during High-Intensity Long-duration Continuous AE Activity (HILDCAA) events: solar cycle phase dependences, Geophysical Research Letters, 41, 1876-1881, https://doi.org/10.1002/2014GL059383.
12. Hajra, R., E. Echer, B. T. Tsurutani, and W. D. Gonzalez (2014), Solar wind-magnetosphere energy coupling efficiency and partitioning: HILDCAAs and preceding CIR-storms during solar cycle 23, Journal of Geophysical Research: Space Physics, 119, 2675-2690, https://doi.org/10.1002/2013JA019646.
11. Hajra, R., E. Echer, B. T. Tsurutani, and W. D. Gonzalez (2013), Solar cycle dependence of High-Intensity Long-Duration Continuous AE Activity (HILDCAA) events, relativistic electron predictors?, Journal of Geophysical Research: Space Physics, 118, 5626-5638, https://doi.org/10.1002/jgra.50530.
10. Hajra, R., S. K. Chakraborty, S. Mazumdar, and S. Alex (2012), Evolution of equatorial irregularities under varying electrodynamical conditions: a multi-technique case study from Indian longitude zone, Journal of Geophysical Research: Space Physics, 117, A08331, https://doi.org/10.1029/2012JA017808.
9. Chakraborty, S. K., R. Hajra, and A. DasGupta (2012), Ionospheric scintillation near the anomaly crest in relation to the variability of ambient ionization, Radio Science, 47, RS2006, https://doi.org/10.1029/2011RS004942.
8. Hajra, R., and S. K. Chakraborty (2011), Equatorial ionospheric responses in relation to the occurrence of main phase of intense geomagnetic storms in the local dusk sector, Journal of Atmospheric and Solar-Terrestrial Physics, 73, 760-770, https://doi.org/10.1016/j.jastp.2011.02.014.
7. Hajra, R., S. K. Chakraborty, and A. DasGupta (2010), Ionospheric effects near the magnetic equator and the anomaly crest of the Indian longitude zone during a large number of intense geomagnetic storms, Journal of Atmospheric and Solar-Terrestrial Physics, 72, 1299-1308, https://doi.org/10.1016/j.jastp.2010.09.015.
6. Chakraborty, S. K., and R. Hajra (2010), Variability of Total Electron Content near the crest of the equatorial anomaly during moderate geomagnetic storms, Journal of Atmospheric and Solar-Terrestrial Physics, 72, 900-911, https://doi.org/10.1016/j.jastp.2010.05.006.
5. Hajra, R., S. K. Chakraborty, and A. Paul (2009), Electrodynamical control of the ambient ionization near the equatorial anomaly crest in the Indian zone during counter-electrojet days, Radio Science, 44, RS3009, https://doi.org/10.1029/2008RS003904.
4. Chakraborty, S. K., and R. Hajra (2009), Electrojet control of ambient ionization near the crest of the equatorial anomaly in the Indian zone, Annales Geophysicae, 27, 93-105, https://doi.org/10.5194/angeo-27-93-2009.
3. Chakraborty, S. K., R. Hajra, and A. Paul (2008), Ionosphere near the anomaly crest in Indian zone during magnetic storm on 13-14 March 1989, Indian Journal of Radio & Space Physics, 37, 396-407, http://nopr.niscair.res.in/handle/123456789/2775.
2. Chakraborty, S. K., and R. Hajra (2008), Solar control of ambient ionization of the ionosphere near the crest of the equatorial anomaly in the Indian zone, Annales Geophysicae, 26, 47-57, https://doi.org/10.5194/angeo-26-47-2008.
1. Chakraborty, S. K., and R. Hajra (2007), Solar control of ambient ionization of the ionosphere near the crest of the equatorial anomaly in the Indian zone, Bulletin of the Astronomical Society of India, 35, 599-605, http://www.ncra.tifr.res.in:8081/~basi/07December/355992007.PDF.