Generation and Loss of New Inner Belts Associated with Solar Energetic Particle Events: A Perspective from Multiple-Satellite Observations

It is puzzling to observe that some Solar Energetic Particle (SEP) events can generate new proton belts in the inner-belt region but not others. One hypothesis is that the new proton belt is the consequence the double-action from a SEP followed by an interplanetary shock: The former loads a seed population of protons at low L-shells and electric field impulses caused by the latter quickly transport those protons even closer to the Earth and adiabatically accelerate them to very high energies. Regarding the loss, it is often observed that the new proton belt suddenly disappear during a moderate geomagnetic storm, and the popular explanation is due to strengthened scattering from the build-up of the ring current. Here we plan to test the above two theories from multiple-point observations from LEO and HEO satellites, which provide particle measurements, in addition to the OMNI upstream solar wind data and geosynchronous observations. Comparing to HEO, LEO measurements from the NOAA POES fleet and SAMPEX provide particle distributions with a high time-resolution and wide energy coverage. Particle and field data from Polar and THEMIS are also to be used in this study. In accordance with the belt-generation hypothesis, we expect for the generation of a new electron inner-belt along with the new proton belt but with a different energy spectrum due to different sources and acceleration processes. As for the loss process, we will look into in-situ magnetic field measurements to compare with global magnetic field models so as to confirm effects of stretching field lines. By adding electron measurements to the analysis, we expect to help differentiate adiabatic effects from others. Through both case and statistical studies, this work will provide a more thorough test on existing hypothesis and possibly new insights on the generation and loss of SEP-caused proton belts by combing various types of observations from multiple space missions.