Abstract
We have analyzed Forbush decreases (Fds) observed at Oulu Super Neutron Monitor (NM) during the period of decline phase of solar cycle 24 with solar and interplanetary phenomena, coronal mass ejections (CMEs), solar flares (SFs), magnetic clouds (MCs) and disturbances in solar wind plasma velocity (SWPV). We have observed that majority of the Forbush decreases (Fds) are associated with halo, partial halo coronal mass ejections (CMEs) and magnetic clouds (MCs). Large positive correlation with correlation coefficient 0.82 has been found between magnitude of Forbush decreases (Fds) and speed of associated CMEs. Moreover, disruptions in solar wind plasma velocity (SWPV) and other types of X-ray solar flares (SFs) are linked to all of the Forbush declines. Large positive correlation with correlation coefficient 0.60 has been found between magnitude of Forbush decreases (Fds) and peak value of associated disturbances in SWPV and 0.58 between magnitude of Fds and magnitude of associated disturbances in SWPV. We have also observed that all the Forbush decreases (Fds) are associated with geomagnetic storms (GMs). The magnitude of Fds and the corresponding geomagnetic storms (GMs) have been found to positively correlate, with a correlation coefficient of 0.41. We have concluded that coronal mass ejections (CMEs) associated with hard X-ray solar flares (SFs) and magnetic clouds (MCs) are much more effective to generate Forbush decreases (Fds) in cosmic ray intensity.
KEYWORDS
Forbush decreases (Fds), Coronal Mass Ejections (CMEs), Solar Flares (SFs), Magnetic Clouds (MCs), Geomagnetic Storms (GMs), Solar Wind Plasma Velocity (SWPV).
Dhanraj1*, Anita Shukla2
1Research Scholar, Department of Physics, Govt. V.Y.T. P.G. Autonomous college, Durg-491001, Chhattisgarh, India
2Department of Physics, Govt. V.Y.T. P.G. Autonomous college, Durg-491001, Chhattisgarh, India