The characteristic pitch angle distributions of 1Â eV to 600Â keV protons near the equator based on Van Allen probes observations

Here we statistically analyze similar to 1 eV to 600 keV hydrogen (H+) PADs near the geomagnetic equator in the inner magnetosphere based on Van Allen Probes measurements, to comprehensively investigate how the H+ PADs vary with different energies, magnetic local times (MLTs), L shells, and geomagnetic conditions.

Our survey clearly indicates four distinct populations with different PADs: (1) a pancake distribution of the plasmaspheric H+ at low L shells except for dawn sector; (2) a bidirectional field-aligned distribution of the warm plasma cloak; (3) pancake or isotropic distributions of ring current H+; (4) radiation belt particles show pancake, butterfly, and isotropic distributions depending on their energy, MLT, and L shell.