Forbush Decreases and Their Relation with Geomagnetic Storms, Interplanetary Magnetic Fields and Solar Wind Plasma Pressure

We have studied Forbush decreases (Fds) in cosmic ray intensity observed during the period of solar cycle 23 and 24 with geomagnetic storms (GMs), interplanetary magnetic fields (IMF) and solar wind plasma pressure (SWPP).We have observed that all the Forbush decreases (Fds) are associated with geomagnetic storms (GMs).It is also seen that magnitude of Forbush decreases (Fds) is positively correlated with magnitude of geomagnetic storms (GMs).Large positive correlation with correlation coefficient 0.60 has been found between magnitude of Forbush decreases (Fds) and magnitude of associated geomagnetic storms (GMs).Further all the Forbush decreases (Fds) are associated with disturbances in interplanetary magnetic fields (IMF) and solar wind plasma pressure (SWPP).Positive correlation with correlation coefficient 0.38 has been found between magnitude of Forbush decreases (Fds) and peak value of associated disturbances in interplanetary magnetic fields (IMF) and 0.40 between magnitude of Forbush decreases (Fds) and magnitude of associated disturbances in interplanetary magnetic fields (IMF).Further all the Forbush decreases (Fds) are associated with disturbances in solar wind plasma pressure (SWPP).Positive correlation with correlation coefficient 0.46 has been found between magnitude of Forbush decreases (Fds) and peak value of associated disturbances in solar wind plasma pressure (SWPP) and 0.44 between magnitude of Forbush decreases (Fds) and magnitude of disturbances in solar wind plasma pressure (SWPP).