The prolonged southward IMF-Bz event of 2–4 May 1998: Solar, interplanetary causes and geomagnetic consequences

Susanta Kumar Bisoi, D. Chakrabarty, P. Janardhan, R. G. Rastogi, A. Yoshikawa, K. Fujiki, M. Tokumaru, Y. Yan

Research output: Contribution to journalArticle

Abstract

A detailed investigation is carried out to understand the prolonged (∼44 h) weakly southward interplanetary magnetic field (IMF-Bz) condition during 2–4 May 1998. In situ observations, during the period, show the passage of an expanding magnetic cloud embedded in an interplanetary coronal mass ejection (ICME), followed up by a shock and an interplanetary discontinuity driven by another ICME. It is the arrival of the ICMEs and the upfront shocks that caused the prolonged southward IMF-Bz condition. The magnetic configuration of the source regions of the IMF associated with the ICME interval was also examined, which showed open magnetic field structures, emanating from a small active region on the north of the heliospheric current sheet (HCS). The structures remained constantly to the north of the HCS, both on 29 April and 1 May, suggesting no change in their polarity. The draping of these outward directed radial field lines around the propagating CMEs in the shocked plasma explains the observed polarity changes of the IMF-Bz at 1 AU. In addition, multiple enhancements were also detected in the geomagnetic field variations, which showed a distinct one-to-one correspondence with the density pulses observed at 1 AU, during 0700–1700 UT on 3 May. The spectral analyses of both the variations showed the same discrete frequencies of 0.48, 0.65, and 0.75 mHz, demonstrating that the solar wind density enhancements can cause detectable global geomagnetic disturbances. The observations, thus, provide a deeper insight into the possible causes and geomagnetic consequences of a prolonged weakly southward IMF-Bz condition.

Original languageEnglish
Pages (from-to)3882-3904
Number of pages23
JournalJournal of Geophysical Research A: Space Physics
Volume121
Issue number5
DOIs
Publication statusPublished - May 1 2016

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coronal mass ejection
IMF
current sheets
magnetic fields
Magnetic fields
Solar wind
causes
polarity
shock
magnetic clouds
augmentation
interplanetary magnetic fields
geomagnetism
Plasmas
solar wind
arrivals
discontinuity
magnetic field
disturbances
intervals

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  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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The prolonged southward IMF-Bz event of 2–4 May 1998 : Solar, interplanetary causes and geomagnetic consequences. / Bisoi, Susanta Kumar; Chakrabarty, D.; Janardhan, P.; Rastogi, R. G.; Yoshikawa, A.; Fujiki, K.; Tokumaru, M.; Yan, Y.

In: Journal of Geophysical Research A: Space Physics, Vol. 121, No. 5, 01.05.2016, p. 3882-3904.

Research output: Contribution to journalArticle

Bisoi, Susanta Kumar ; Chakrabarty, D. ; Janardhan, P. ; Rastogi, R. G. ; Yoshikawa, A. ; Fujiki, K. ; Tokumaru, M. ; Yan, Y. / The prolonged southward IMF-Bz event of 2–4 May 1998 : Solar, interplanetary causes and geomagnetic consequences. In: Journal of Geophysical Research A: Space Physics. 2016 ; Vol. 121, No. 5. pp. 3882-3904.
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