Heliospheric Modulation of GCR at Mid and High Latitudes

Abstract

The variations of Galactic Cosmic Ray (GCR) as compared with the behaviour of various solar activity indices, heliospheric parameters and the geomagnetic index Ap during 1999-2015, which covers part of cycles 23 and cycle 24 have been studied.  Two sets of data were considered, consisting respectively of all days of the month and the five quietest days. Neutron Monitor Stations of Moscow and Rome (mid latitude stations) and Inuvik and Oulu (High latitude stations) were employed. Cosmic Ray (CR) wave characteristics were obtained by the harmonics method.  The mean, diurnal amplitude of the first, second, and third harmonics were calculated and profiled. Furthermore, correlation analysis was carried out to determine the association between parameters. Results showed that the total magnetic field BT and the sunspot number (SSN) showed the strongest association with CR in both quiet conditions and all day conditions considered. The higher harmonics showed a slightly stronger association with CR than lower harmonics. A time-lag of about 12-15 months was observed for SSN suggesting a potential for predicting CR flux, while the total magnetic field had a zero lag for all the heliospheric parameters considered.