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Title: Heliographic distribution of bright solar flares and association of Forbush-decreases with flares and coronal mass ejections
Authors: Mishra, A P
Mishra, B N
Gupta, Meera
Mishra, V K
Issue Date: Aug-2008
Publisher: CSIR
Abstract: Major solar flare events have been selected to study the heliographic distribution of solar flares during solar cycle 23. The occurrence of Forbush decreases (FDs), bright solar flares; solar flare index, coronal mass ejections (CMEs), average solar magnetic field and solar wind velocity have been studied for the period 1996-2006. It is found that the solar flare index in northern and southern hemisphere represents the cumulative activity of solar flare in both hemispheres. Though, the bright solar flares are equally distributed in the entire solar region, majority of the bright solar flares responsible for FDs (≥ 4% magnitude) are located in the north-east region of the solar disk. Out of 41 FDs, 88% are found to be associated with halo (central position angle ≈ 360) and partial halo (central position angles ≥ 120) CMEs (coronal mass ejections) and 55% with bright solar flares of importance ≥ 1B. The abrupt increase in average solar magnetic field and solar wind velocity has also been found to be a necessary condition for producing FDs. The occurrence of non-recurrent type FDs are more frequent than recurrent type FDs. In latitudinal distribution, northern hemisphere is more dominant than the southern hemisphere in producing FDs. It is also found that eastern hemisphere is more effective as compared to western hemisphere to produce FDs in longitudinal distribution during the aforesaid period.
Page(s): 237-243
ISSN: 0376-4710
Appears in Collections:IJRSP Vol.37(4) [August 2008]

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