Harmonics of exceptionaly low amplitude anisotropic wave train events in cosmic ray intensity

The unusually low amplitude anisotropic wave train events (LAEs) in cosmic ray intensity using the ground based Deep River neutron monitor data has been studied during the period 1991–94. It has been observed that the phase of the diurnal anisotropy for the majority of the LAE events remains in the co-rotational direction. However, for some of the LAE events the phase of the diurnal anisotropy shifts towards earlier hours as compared to the annual average values. On the other hand, the amplitude of the semi-diurnal anisotropy remains statistically the same, whereas phase shift-towards later hours; a similar trend has also been found in case of tri-diurnal anisotropy. The high-speed solar wind streams do not play a significant role in causing the LAE events. The occurrence of LAE is independent of the nature of the Bz component of IMF polarity. Published in Astrofizika, Vol. 50, No. 2, pp. 313–324 (May 2007).