Characteristics of cosmic ray intensity on the onset of coronal mass ejections

Coronal Mass Ejections (CMEs) are large, energetic expulsions of mass and magnetic fields from the Sun; they can significantly affect large volumes of the heliosphere and appear to be a key cause of geomagnetic storms. The present study deals with the influence of Asymmetric 'Full' Halo CMEs, Partial Halo CMEs, Asymmetric and Complex 'Full' Halo CMEs and 'Full' Halo CMEs on cosmic ray intensity during 2005. The data of ground based neutron monitor of Inuvik and CME events observed with instruments onboard and Wind spacecraft have been used in the present analysis. The method of superposed epoch (Chree) analysis has been used to the arrival times of these CMEs. It is noteworthy that the occurrence of Asymmetric 'Full' Halo CMEs is greater than the other CMEs during the period of investigation. The cosmic ray intensity found to decrease 10 days before the onset of CMEs and reaches to its minimum 3 days after the event for Asymmetric 'Full' Halo CMEs, Partial Halo CMEs and Asymmetric and Complex 'Full' Halo CMEs. On the onset of asymmetric and complex full halo CMEs the intensity of cosmic ray fluctuates quite frequently as compared to other CMEs. Significant enhancement is seen in the cosmic ray intensity two days after the onset of 'Full' Halo CMEs, which is continue for two days then decreases rapidly. PACS: 96.40.Kk, 96.40. -z, 96.40.cd