nan Badruddin

Cosmic ray modulation: Effects of high speed solar wind streams

Based on their source of origin, high speed streams detected in the solar wind plasma have been classified into two classes, coronal hole and solar flare associated streams. Observed heliospheric plasma and field parameters of these streams such as speed, field strength and its variance have been utilized in a systematic manner in order to see their effects in cosmic ray modulation. It is found that flare associated streams are much more effective in modulation than streams from coronal holes. Inspite of the possibility that solar wind structures during two types of streams might be different, the field variance appears to be the most cricial parameter responsible for this difference in their effectiveness in modulation.

Coupling of the Solar Wind and the Magnetosphere

The field orientation in transient and co-rotating structures that are ejected from the Sun and evolve in interplanetary space is crucial in reconnection between the solar wind and the magnetosphere. However, fluctuations in the magnetic field and/or enhancements in plasma density may influence the coupling between the solar, interplanetary, and magnetospheric fields. Consequently, the geo-effectiveness of solar wind structures with enhanced field variance and density are likely to increase. We study the effects of both enhanced field fluctuations and enhanced plasma density on the magnetic reconnection/coupling efficiency. We consider solar plasma and field properties, particularly the field fluctuation and plasma density before, during, and after the interplanetary events with geospace consequences. Considering the geo-effectiveness of different magnitude as a measure of the coupling efficiency and reconnection rate, we study the influence of these enhancements on the solar wind–magnetosphere coupling efficiency, during southward field orientation within the interplanetary structures.