ИСТИНА

We analyze several cases of THEMIS spacecraft observations of EMIC waves in proton, He+, and O+ frequency bands in various local time sectors and L shells. We selected the events during which the energetic proton precipitation was observed by low-orbiting POES spacecraft in the conjugated region. By using the data on the spectral intensity of EMIC waves, the geomagnetic field, and the plasma density we calculated the pitch-angle diffusion coefficients of energetic protons for various energies and pitchangles. The calculations were performed under the assumption that the ambient plasma consisted of three ion species, i.e., protons, He+, and O+ ions. The results of calculations were compared with the measured pitch-angle distributions of energetic protons in the magnetosphere and with the energy of precipitated protons. On the whole, these parameters of energetic protons are in agreement with those which can be expected on the basis of the calculated pitch-angle diffusion coefficients.