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Title: Features of long term evolution of solar wind and IMF and their signature on geomagnetic activity
Authors: Nair, V Sanalkumaran
Nayar, S R Prabhakaran
Keywords: Geomagnetic activity
Coronal holes
Solar maximum
Solar minimum
Solar wind velocity
Interplanetary magnetic field
Issue Date: Jun-2009
Publisher: CSIR
Abstract: The geomagnetic activity is mainly controlled by variations in the solar wind and interplanetary magnetic field (IMF) features. The solar wind data available during 1965-2004 has been utilized to study large scale features in interplanetary medium and their signature on geomagnetic activity. The solar wind plasma, IMF and geomagnetic activity are found to evolve with the phase of solar cycle. The evolution and role of solar wind streams and IMF field strength (B) in shaping long term features of planetary magnetic activity index (Ap) index have been studied. The high speed streams are caused mainly by the increase in coronal hole activity around the declining phase of solar cycle and by the presence of large number of coronal transients around solar maximum. Association between coronal holes and geomagnetic activity is clear from the simultaneous presence of high negative correlation between solar wind velocity (Vsw) and density (n) and the enhancement in geomagnetic activity during declining phase of solar cycle. During this period, Vsw and Ap index also exhibit good correlation. Around solar maximum periods, good correlation is found between B and Ap index. These results suggest that Vsw has a major role in deciding the geomagnetic activity around declining phase and IMF magnitude has a major role in deciding geomagnetic activity around solar maximum.
Description: 134-137
ISSN: 0975-105X (Online); 0367-8393 (Print)
Appears in Collections:IJRSP Vol.38(3) [June 2009]

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