Abstract
We study the geomagnetic disturbances and solar wind plasma/field properties during the passage of High Speed Solar Wind Streams (HSS) emanating from the sun. We consider the HSS detected during the period 1996–2011. For this study, we divided the geomagnetic disturbances that occurred during the passage of these HSS into four groups based on the level of geomagnetic activity. We analyze the solar plasma/field variations during the disturbances of different levels. We apply the method of the superposed epoch analysis to study the average behavior of geomagnetic disturbances and selected plasma/field parameters during the passage of HSS producing geomagnetic activity of different level. We also study the relation between the geomagnetic activity and solar plasma/field parameters during the passage of the HSS.