Distribution of MHD wave activity in the foreshock region and properties of backstreaming protons

Magnetic field and plasma data obtained by ISEE 2 experiments in the earth's foreshock region have been used, in conjunction with a shock model, to correlate with geometrical parameters the intensity of MHD turbulence and some moments of the distributions of back‐streaming protons. The geometrical parameters are the distance of the observation point from the proton foreshock boundary and the distance from the shock surface. The results obtained allow a preliminary discussion of two basic problem of the physics of the foreshock. These are (1) the relative role of shock structure and/or wave particle interaction in determining the form of the backstreaming ion distributions and (2) the physical mechanisms determining the observed saturation of the MHD turbulence.