edu.ucar.opensky::articles:21136 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T02:23:52.950896 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7br8vr2 The characteristic pitch angle distributions of 1 eV to 600 keV protons near the equator based on Van Allen probes observations 2017-09-21T00:00:00Z publication https://n2t.org/ark:/85065/d7br8vr2 https://doi.org/10.1002/2017JA024421 Yue, Chao author Bortnik, J. author Thorne, R. M. author Ma, Q. author An, X. author Chappell, C. R. author Gerrard, A. J. author Lanzerotti, L. J. author Shi, Q. author Reeves, G. D. author Spence, H. E. author Mitchell, D. G. author Gkioulidou, M. author Kletzing, C. A. author UCAR/NCAR - Library publisher Understanding the source and loss processes of various plasma populations is greatly aided by having accurate knowledge of their pitch angle distributions (PADs). 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. Meanwhile, the pancake distribution of ring current H+ moves to lower energies as L shell increases, which is primarily caused by adiabatic transport. Furthermore, energetic H+ (> 10 keV) PADs become more isotropic following the substorm injections, indicating wave-particle interactions. The radiation belt H+ butterfly distributions are identified in a narrow energy range of 100 < E < 400 keV at large L (L > 5), which are less significant during quiet times and extend from dusk to dawn sector through midnight during substorms. The different PADs near the equator provide clues of the underlying physical processes that produce the dynamics of these different populations. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright 2017 American Geophysical Union. None eng geoscientificInformation