DIFFUSION OF RADIATION BELT PROTONS BY WHISTLER WAVES

Whistler waves propagating near the quasi-electrostatic limit can inte ract with energetic protons (similar to 80 - 500 keV) that are transpo rted into the radiation belts. The waves may be launched from either t he ground or generated in the magnetosphere as a result of the resonan t interactions with trapped electrons. The wave frequencies are signif icant fractions of the equatorial electron gyrofrequency, and they pro pagate obliquely to the geomagnetic field. A finite spectrum of waves compensates for the inhomogeneity of the geomagnetic field allowing th e protons to stay in gyroresonance with the waves over long distances along magnetic field lines. The Fokker-Planck equation is integrated a long the flux tube considering the contributions of multiple-resonance crossings. The quasi-linear diffusion coefficients in energy, cross e nergy/ pitch angle, and pitch angle are obtained for second-order reso nant interactions. They are shown to be proportional to the electric f ields amplitudes. Numerical calculations for the second-order interact ions show that diffusion dominates near the edge of the loss cone. For small pitch angles the largest diffusion coefficient is in energy, al though the cross energy/ pitch angle term is also important. This may explain the induced proton precipitation observed in active space expe riments.