Galactic Cosmic Ray Variability In The High And Mid Latitudes During Solar Cycles 22 And 23

ABSTRACT

Galactic cosmic rays are modulated in the hliosphere primarily due to the global merged interaction

regions with intense magnetic field which leads to a decrease in the galactic cosmic rays throughout the

heliosphere. Using long term averages of solar wind (SW) component parameters in addition to cosmic

ray count rates of two high latitude Neutron monitor stations (Apatity and Thule) and two mid latitude

stations (Newark and Tbilisi) with different rigidity cut-offs, we analyzed the effect of these SW

components on the counts rates under different interplanetary magnetic field (IMF) disturbance levels.

From first order partial correlation, we found that the total interplanetary magnetic field (Total B) was

the most dominant modulating parameter especially during quiet conditions and the solar wind dynamic

pressure (SWDP) was more effective during disturbed conditions. The influence of the more subtle

parameters like solar wind speed (SWS), Z component of IMF (Bz) and solar wind density were masked

by these dominant parameters vis IMF (Total B) and SWDP. Also, cosmic ray count rates on these

stations studied showed similar annual variation trend, with station of lowest cut-off rigidity having highest amplitude and vice versa, confirming cut-off rigidity as another important modulating factor.