Simultaneous Observations of Cosmic Ray Particles in a Corotating Interplanetary Structure at Different Solar Distances between 0.3 and 1 AU from HELIOS 1 and 2 and IMP 7 and 8

Abstract

From December 1975 to June 1976 we observed an evolving recurrent proton enhancement with IMP 7/8 and Helios 1/2 at different distances from the sun. The corotating character is established over 4 solar rotations. Due to the unique constellation in March 1976 simultaneous measurements were possible which allowed a study of the radial development undisturbed by temporal effects. The intensity variation of the ~4 - 13 MeV protons between 0.43 and 1 AU revealed a sudden increase to a large positive gradient (+329 %/AU) in the leading edge of the event. This value is consistent with a major source outside 1 AU. We suggest an interplanetary acceleration which becomes sufficiently effective within a fast solar wind stream.