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Ann. Geophys., 24, 3569-3583, 2006
www.ann-geophys.net/24/3569/2006/
© European Geosciences Union 2006
Low-latitude geomagnetic signatures during major solar energetic particle events of solar cycle-23
R. Rawat, S. Alex, and G. S. Lakhina
Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai-410218, India
Abstract. The frequency of occurrence of disruptive transient processes in
the Sun is enhanced during the high solar activity periods. Solar
cycle-23 evidenced major geomagnetic storm events and intense
solar energetic particle (SEP) events. The SEP events are the
energetic outbursts as a result of acceleration of heliospheric
particles by solar flares and coronal mass ejections (CMEs). The
present work focuses on the geomagnetic variations at equatorial
and low-latitude stations during the four major SEP events of 14
July 2000, 8 November 2000, 24 September 2001 and 4 November 2001.
These events have been reported to be of discernible magnitude
following intense X-ray flares and halo coronal mass ejections.
Low-latitude geomagnetic records evidenced an intense main phase
development subsequent to the shock impact on the Earth's
magnetosphere. Satellite observations show proton-flux
enhancements associated with solar flares for all events.
Correlation analysis is also carried out to bring out the
correspondence between the polar cap magnetic field perturbations,
AE index and the variations of low-latitude magnetic field. The results presented in
the current study elucidate the varying storm development
processes, and the geomagnetic field response to the plasma and
interplanetary magnetic field conditions for the energetic events.
An important inference drawn from the current study is the close
correspondence between the persistence of a high level of proton
flux after the shock in some events and the ensuing intense
magnetic storm. Another interesting result is the role of
the pre-shock southward IMF Bz duration in
generating a strong main phase.
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