Comparative Study Of Symmetric And Asymmetric Forbush Decreases With Disturbances In Solar Wind Parameters

Abstract

In this manuscript we have to consider those symmetric cosmic ray decreases which have magnitude≥ 3% and those asymmetric cosmic ray intensity decreases which have magnitude ≥ 4.0% for the time span of 17 years from 1997-2013. For this time span we have identified 47 and 74 symmetric and asymmetric cosmic ray intensity decreases respectively. In this manuscript we have presented the correlation between symmetric and asymmetric cosmic ray intensity decreases (Fds) with some solar wind plasma parameters like plasma density and velocity. Out of 47 symmetric cosmic ray decreases, 41 (87.23 %) symmetric cosmic ray intensity decreases have been found to be associated with jump in solar wind plasma density (JSWD) events and 37 (78.72%) have been found to be associated with jump in solar wind plasma velocity (JSWV) events. Magnitude of symmetric cosmic ray intensity decreases are negatively correlated with magnitude of jump in solar wind plasma density and magnitude of jump in solar wind plasma velocity with co-relation co-efficient -0.15 and -0.16 respectively. Out of 74 asymmetric cosmic ray decreases, 70 (94.59%) asymmetric cosmic ray intensity decreases have been found to be associated with jump in solar wind plasma density (JSWD) events and 67 (90.54%) have been found to be associated with jump in solar wind plasma velocity (JSWV) events. Again the magnitude of asymmetric cosmic ray intensity decreases are positively correlated with magnitude of jump in solar wind plasma density and magnitude of jump in solar wind plasma velocity with co-relation co-efficient 0.25 and 0.23 respectively.