Spherical harmonic analysis of worldwide cosmic ray variations during geomagnetic storms

The spherical harmonic analysis is performed on a number of cosmic ray storms on the basis of the records collected from 26 stations whose asymptotic directions are reasonably uniformly distributed in the geographic coordinates. Here, we report in detail the results for 2 events, September 21–25, 1966, and March 20–26, 1966; the results for 8 other events are given in tabular form. It is shown that the worldwide component (C0) varies closely with the simultaneous cosmic ray variation observed by the Pioneer 7 space probe and for the September 23, 1966, event. The analysis also provides the maximum anisotropic component flux (P) and its asymptotic direction; both vary considerably even during single events. On September 23, 1966, P temporarily reached a value as large as 4.3%.