[PEM19-P11] Observational study on mass and charge dependence of plasma energization in the inner magnetosphere and near-Earth magnetotail
Keywords:Ring current, Magnetic storms, Substorms and dipolarization, Ion composition, Arase
Energy spectra of singly-charged ions (H+, He+, O+) show mass dependence, with He+ and O+ having harder spectra than H+. The spectral slope of doubly-charged ions (He++, O++) is steeper for H++ than O++. For ions with the same mass, singly-charged ions show harder spectra than doubly-charged ones. The results indicate that energization processes in the near-Earth magnetotail are more dependent on mass than charge. This suggests that the ion energy gain in the magnetotail is not determined by a complete displacement across the global electric field potential only. An important factor is likely the limited spatial scale of the electric field associated with narrow flow channels during magnetic field reconfiguration (dipolarization), which has been reported comparable to gyro-radii of heavy ions.