Nonlinear wave-particle interaction in the magnetospheric region leading to polar and equatorial proton precipitation

Summary form only given. The interaction between a bouncing proton and a kinetic Alfven wave in the magnetosphere was studied. using the full set of the equations of motion. The critical field amplitude for the onset of chaos is determined by the observations that the turning points suddenly vary randomly and cross field diffusion suddenly becomes non-zero average at that field amplitude. As the field amplitude is increased further, one can calculate the turning points of the bouncing proton to show that the second adiabatic invariant is violated so that the proton can diffuse through the loss cone into the polar region. The radial displacement of the proton motion has also been calculating, showing that it, in fact, drifts radially downward. This explains the experimental observation of precipitation in the equatorial region.