Energy spectra of ring current protons are crucial to understanding the ring current dynamics. Based on high-quality Van Allen Probes RBSPICE measurements, we investigate the global distribution of the reversed proton energy spectra using the 2013-2016 RBSPICE datasets. The reversed proton energy spectra are characterized by the distinct flux minima around 50 - 100 keV and flux maxima around 200 - 400 keV. Our results show that the reversed proton energy spectrum is prevalent inside the plasmasphere, with the occurrence rates > 90% at L ~ 2 - 4 during geomagnetically quiet periods. Its occurrence also manifests a significant decrease trend with increasing L-shell and enhanced geomagnetic activity. It is indicated that the substorm-associated processes are likely to lead to the disappearances of the reversed spectra. These results provide important clues for exploring the underlying physical mechanisms responsible for the formation and evolution of reversed proton energy spectra.

The planetary magnetic fields in the solar system deflect/reflect solar wind at bow shocks in front of their magnetospheres, protecting the planets from direct solar wind bombardment. Indirect evidences suggest that the sporadic magnetic anomalies on the Moon, i.e., the small-scale magnetic fields, do the same, protecting the lunar surface below and even modifying the chemical/optical properties there. It is, however, still unclear how these anomalies interact with solar wind because of lack of in-situ observations. Two key remotely-sensed symptoms, i.e., the lunar reflected ions and the associated ~1Hz waves, are organized in a particular coordinate system here to diagnose the solar wind interaction. We show that particles are reflected around the specular direction above the lunar surface, hinting an electric-field effect in the reflection, and that whistler wings form, suggesting a distinct solar wind interaction scenario to that of a giant planetary field.

During geomagnetic storms, magnetospheric wave activity drives the ion precipitation which can become an important source of energy flux into the ionosphere and strongly affect the dynamics of the Magnetosphere-Ionosphere (MI) coupling. In this study, we investigate the role of Electro Magnetic Ion Cyclotron (EMIC) waves in causing ion precipitation into the ionosphere using simulations from the RAM-SCBE model with and without EMIC waves included. The global distribution of H-band and He-band EMIC wave intensity in the model is based on three different EMIC wave models statistically derived from satellite measurements. Comparisons among the simulations and with observations suggest that the EMIC wave model based on recent Van Allen Probes observations is the best in reproducing the realistic ion precipitation into the ionosphere. Specifically, the maximum precipitating proton fluxes appear at L=4-5 in the afternoon-to-night sector which is in good agreement with statistical results, and the temporal evolution of integrated proton energy fluxes at auroral latitudes is consistent with earlier studies of the stormtime precipitating proton energy fluxes and vary in close relation to the Dst index. Besides, the simulations with this wave model can account for the enhanced precipitation of <20 keV proton energy fluxes at regions closer to earth (L<5) as measured by NOAA/POES satellites, and reproduce reasonably well the intensity of <30 keV proton energy fluxes measured by DMSP satellites. It is suggested that the inclusion of H-band EMIC waves improves the intensity of precipitation in the model leading to better agreement with the NOAA/POES data.

Using the data from Van Allen Probe A and B, we investigate rapid enhancements of relativistic electrons in the Earth’s outer radiation belt caused by the intense substorms (AEmax > ~ 900 nT) for 29 events from January 2013 to April 2015. These intense substorms may occur during the storm main phase or recovery phase. Based on the different substorm evolution characteristics, the intense substorms are divided into isolated substorm activities and continuous substorm activities. In this study, we set a criterion for rapid enhancements when the electron phase space densities (PSDs) for μ = 1096, 2290, and 3311 MeV/G increased by more than 2 times in 9 hours. In the time interval of 9 hours, the local acceleration of chorus waves is the dominant process for accelerating the seed populations (100s keV) up to MeV energies. Our statistical results show that enhanced chorus waves and seed electrons during the intense substorms are observed in the outer radiation belt. Continuous substorm activities can more rapidly (< 9 h) and efficiently accelerate relativistic electrons in the outer radiation belt than isolated substorm activity. During the intense substorms, MeV electron injections could contribute to rapid enhancements of relativistic electrons in the outer radiation belt. Our statistical study suggests that the intense substorms during geomagnetic storms have a significant effect on the rapid variations of relativistic electron dynamics.