Tri-diurnal anisotropy of cosmic ray daily variation for the solar cycle 23

Abstract

An extensive study of tri-diurnal anisotropy of cosmic ray daily variations for the period 1996 – 2006 has been carried out using cosmic ray neutron monitor data of Kiel and Beijing. The daily and yearly averages of tri-diurnal wave amplitude and phase have been obtained to observe long term behaviour of third harmonic of cosmic ray daily variation. The relation between amplitudes and phases (annual and daily averages) of tri-diurnal data for these two different cut off rigidities has been shown. No long-term variational trend is seen in tri-diurnal anisotropy. On day-to-day analysis, a well defined peak in tri-diurnal amplitude between 0.06% and 0.010% is observed.