Observed distribution functions of H, He, C, O, and Fe in corotating energetic particle streams: Implications for interplanetary acceleration and propagation

Distribution functions for H, He, C, O, and Fe derived from our IMP 8 measurements of approx.0.15 to approx.8 MeV per nucleon particles in three corotating streams observed near Earth are shown to have a simple exponential dependence on the particle speed. The e-folding speed, upsilon0, is typically 0.01c, is found to be the same for the distribution functions of all elements examined, and varies little from one corotating event to the next. The relative abundance of energetic particles in these events resemble most closely the solar coronal composition and thus, presumably, that of the solar wind. These results may imply that the acceleration of these particles, which occurs in corotating interaction regions at several AU from the Sun, is by a statistical process