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IJRSP Vol.37(6) [December 2008] >


Title: North-South asymmetry in solar wind & geomagnetic activity and its solar cycle evolution
Authors: Nair, V Sanalkumaran
Nayar, S R Prabhakaran
Keywords: Solar wind velocity
Geomagnetic activity index
Interplanetary magnetic field
Solar activity
Solar North-South asymmetry
Issue Date: Dec-2008
Publisher: CSIR
Abstract: The unequal distribution of various aspects of solar activity between the north and south hemisphere of the Sun is well known for over a century. Analysis of solar wind data observed during 1964 - 2004 showed that solar wind velocity (Vsw), interplanetary magnetic field (IMF) Bz component and geomagnetic activity index (Ap) exhibit a clear heliospheric north-south asymmetry. In general, amplitude of the north-south asymmetry is maximum during the minimum phase of solar cycle. For Vsw and IMF Bz component, amplitude of the asymmetry is greater during even cycles 20 and 22 compared to the odd cycles 21 and 23. The phase of the asymmetry of IMF Bz reverses every cycle with a northern dominance in even cycles and southern dominance in odd cycles. The asymmetry of Vsw has a northern dominance during cycles 20 and 23 and southern dominance during cycles 21 and 22. Thus, for Vsw, the amplitude of the asymmetry and IMF Bz, both the amplitude and phase exhibit a 22-year period. The asymmetry of Ap index appears similar to that of solar wind velocity. The asymmetry in solar wind velocity and geomagnetic activity may be due to the existence of a relic solar magnetic field in the solar convection zone.
Page(s): 391-395
ISSN: 0367-8393
Source:IJRSP Vol.37(6) [December 2008]

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