Abstract:
A comparative study of the diurnal variation of cosmic ray (CR) intensity has been performed on geomagnetically quiet days (QD) and all days (AD) using neutron monitor data for the year 1987. It is observed that even though there are significant differences on individual days, the QD have been found to be more informative as compared to AD. Further, on long term basis the phase of the diurnal anisotropy acquired its usual corotational direction in 1980. It is observed to remain constant for the later period up to 1990 adding further to the hypothesis of 22-year periodic variation of diurnal anisotropy. Thus, the diurnal anisotropy is observed to be consistent with the convection-diffusion model.
