Cosmic ray anisotropic variations with solar activity during quiet days

The study of cosmic ray (CR) diurnal anisotropy using the Deep River neutron monitor data has been made with solar activity (sunspot numbers) during quiet days (QD) for the period 1964-1995. The amplitude of the diurnal anisotropy during QD was found to remain low in the time of the minimum solar activity. However it remained high during the declining phase of solar activity cycle. The anisotropy direction gradually shifts towards earlier hours till 1976 (solar activity minimum) and to later hours till 1991 (solar activity minimum), and then again towards earlier hours. The time of maximum shows a 2-year periodicity in the cosmic ray diurnal anisotropy. The anisotropy seems to be completely dominated by two components - one in the 1600 h and the other in the 1200 h direction. (Authors)