Effects of Magnetic clouds, IP shocks, and CMEs on cosmic ray intensity vari- ations.

Abstract

The Magnetic clouds (CMEs) is a particular type of interplanetary ejection which showed a smooth rotation of the magnet- ic field. Other features of these events are high magnetic field strength and low temperatures. Ninety five MCs were observed during the period of 1996 to 2006. The influence of these MC events on cosmic ray intensity variation has been examined. In this work the role of interplanetary shocks and coronal mass Ejections (CMEs) are also investigated. The results of our analysis indicate that mag- netic clouds in combination with interplanetary shock produce cosmic ray decrease. Further the MCs and IP shock associated with CMEs produce large forbush type decrease in cosmic ray intensity. It is also noticed that the decrease starts earlier from the onset time of magnetic clouds. Out of 95 MC events, 47 MCs are lying in this category. Only four MC events are found to be associated with only shocks, which also show a decrease but lower than the first category. The observations demonstrate that without IP shocks and CME associated MCs could not trigger a cosmic ray decrease. In this work, we observe also higher geomagnetic activity during