Ulysses observations of short-period (≤ 30 days) modulation of the galactic cosmic rays

Abstract

A frequency analysis of the short-period modulation of the GCR as seen by instruments aboard Ulysses shows interesting temporal variations. In particular, during an approximate five-month period from December 1993 to May 1994, the modulation was not the usual 26 days but more than 29 days. The CIR-associated MeV ions did not exhibit this period shift.