No abstract

A detailed study has been conducted on the long-term changes in the diurnal variation of cosmic rays in terms of high and low amplitude wave trains event (HAEs/LAEs) during the period 1996-2008 (solar cycle 23), using the neutron monitor data from Kiel neutron monitoring station. As such, 17 HAE and 48 LAE cases have been detected and analyzed. These HAEs appear quite dominantly during the declining phase as well as near the maximum of the solar activity cycle 23. In contrast, the low amplitude events (LAEs) are inversely correlated with solar activity cycle. In fact, LAEs appear quite dominantly during the minimum phase of the solar activity. When we compare our results for diurnal phase with that observed on an annual average basis, we notice no significant diurnal phase shift for HAEs as well as for LAEs. Moreover, we find that the high-speed solar wind streams (HSSWS) do not play any significant role in causing these variations. These results are discussed on the basis of that observed in earlier cycles.Key words. Cosmic rays-diurnal variation-high amplitude anisotropic events-low amplitude anisotropic events-solar cycle-solar wind speed.

Abstract:The solar modulation of Galactic Cosmic Rays (GCR) is revealed in the record of neutron monitors in terms of daily variation. Day-to-day and long term basis daily variations have been investigated for the recent period from 1965 to 2015 along with geomagnetic disruption index Ap on twelve-monthly average basis. Here Ap index has been used as a placeholder for the solar bring on interplanetary disturbances. It is create that, in general on an annual average basis, both the diurnal amplitude as well as the diurnal phase is considerably lower in the years of low Ap values, through the period 1965 to 2015. Such as a result was also informed for the earlier periods. However, anomalous and determined results for the diurnal variations have been received when the daily values of Ap are diffused in five groups with the first group demonstrating low Ap condition (i.e. quite periods) and the last group naturally representing the disturbed conditions.