Cosmic ray intensity increases detected by Aragats Space Environmental Center monitors during the 23rd solar activity cycle in correlation with geomagnetic storms

摘要

Interplanetary coronal mass ejections (ICMEs) dominate the intense geomagnetic storm (GMS) occurrences, and simultaneously, they are correlated with the variations of the spectra of particles, ranging from the isothermal solar wind ions to GeV energy protons and fully stripped nuclei. The aim of this paper is to get more insight in the correlations of the ICME parameters with geospace parameters, including the Dst index and the secondary cosmic ray flux. Our observations of GMS occurring during the 23rd solar activity cycle demonstrate that the count rate increase during GMS occurs coherently (or up to 1 h in advance) with Dst changes. We show that the ratio between the increases of neutron and charged fluxes is approximately constant in a large range of the GMS severity (-470 to 20 nT). The neutron flux always undergoes larger changes compared to the charged component. The difference in peak amplitude can be explained by the fact that lower-energy primary particles produce neutrons compared to the primaries that generate electrons and muons reaching the Earth's surface. We also illustrate that the main driver of GMS is the southward В_z component of the magnetic field of the ICME. Thus the information on the flux changes for different secondary particles helps to "test" the models of the interplanetary magnetic field and the magnetosphere for understanding of the level of disturbance and the specific mechanisms leading to cutoff rigidity reduction.