On the diurnal variation coefficients of the nucleonic component of cosmic rays

Abstract

The expected amplitudes, as well as the time shift due to geomagnetic bending, of the diurnal waves have been calculated for 27 cosmic ray neutron monitors for the recent shapes of the diurnal, semidiurnal and tridiurnal anisotropies. The calculations are performed for latitude dependence of the form, cos n λ and rigidity dependence of the formR β exp [(1−R)/R 0] where λ is the asymptotic latitude,R is the rigidity in GV, andn, β andR 0 are constants. For the diurnal anisotropy, the calculations are given forn=1, β=−0.4, 0.0, +0.4, +0.8,R 0=∞ and maximum cutoff rigidity =90 GV, while for semidiurnal and tridiurnal anisotropies the results are given forn=1, 2, β=1, 2 andR 0=50, 90 GV. Moreover, the calculation of the attenuation due to the latitude effect, the smoothing effect, and the mean latitude and mean cone broadening are given for the different concerned anisotropies. The presently calculated coefficients for diurnal variation are significantly smaller than those calculated previously due to the careful selection of the used parameters. A considerable increase in the time shift due to geomagnetic bending is only found in the wide cone stations. The relation between the mean latitude, the cone broadening, the time shift, and the expected amplitude for all diurnal components and the minimum cutoff rigidity of the different stations are discussed.