Pitch-Angle Diffusion of Energetic Protons upon Their Interaction with EMIC Waves: Comparison of Calculation Results with THEMIS and NOAA/POES Data
We analyze several cases of THEMIS spacecraft observations of EMIC waves in proton and He+ 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 conjugate 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 at low pitch-angles. 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 energy of precipitated protons. On the whole, the energies of precipitated energetic protons are in agreement with those which can be expected on the basis of the calculated pitch-angle diffusion coefficients.
KeywordsEMIC wave The energetic proton precipitation The pitch-angle diffusion
We thank the THEMIS Project Team (project manager V. Angelopoulos) for providing free access to project data (http://themis.ssl.berkeley.edu), and NOAA for providing POES satellite data (https://www.ngdc.noaa.gov/stp/satellite/poes/dataaccess.html). This work was supported by the Russian Science Foundation, project no. 15-12-20005.
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