Cosmic ray variations and magnetic field fluctuations in the outer heliosphere

Abstract

We have formally confirmed that galactic cosmic ray intensity variations measured by Voyager 2 during recovery from solar maximum are caused by traveling compressions and rarefactions in the mean interplanetary magnetic field. We used Voyager's magnetic field data as input to a time‐independent, spherically symmetric, cosmic ray transport equation in the force field approximation. The solutions closely followed the count rate of cosmic rays greater than 75 MeV/nucleon over 4 years, during the recovery phase of the 11‐year solar‐driven cosmic ray cycle. This strongly supports prior theoretical assertions that turbulent interaction regions traveling with the solar wind are the major cause of the solar cycle variation of galactic cosmic rays in the ecliptic region.