GEM: Multipoint Observations and Global Modeling of Energetic Particle Deep Penetration into the Low L Region of Earth's Inner Magnetosphere

Understanding the relativistic particle environment surrounding Earth is vital to predict and mitigate space weather effects. These effects include damage to satellites in low-Earth orbit. This project addresses an important question of how particles are accelerated in the inner magnetosphere through a combination of observational studies and state-of-the-art modeling. Two early career researchers are supported.

The main goal of this project is to investigate and quantify the role of electric fields in the deep penetration of energetic electrons and protons using data from the Van Allen Probes and THEMIS as well as modeling with the RCM-E and a 3-D particle tracer. Specific science questions to be addressed are: 1) Based on the multipoint observations, what are the quantitative differences between energetic electron and proton deep penetration into the low L region in penetration depth, frequency, timing, and MLT distribution? 2) Based on the multipoint observations, what is the spatiotemporal evolution of electric fields in the inner magnetosphere during energetic particle deep penetration events? 3) To what extent can the RCM-E represent the observed electric fields in the inner magnetosphere during deep penetration events? 4) To what extent can the electric fields given by RCM-E explain the differences in deep penetration of inner magnetospheric energetic particles of different species and/or energies?

To answer these science questions, energetic particle deep penetration events down to L<4 will be identified using data from the Van Allen Probes, and the penetration depth, timing, and MLT dependence will be examined. The electric field measurements from EFW on Van Allen Probes and EFI on THEMIS will be examined, and the spatiotemporal evolution of electric fields will be investigated. The RCM-E will be used to model self-consistent, time-varying electric fields in the inner magnetosphere to be compared to the observations.

The modeled electric fields will then be embedded into a particle tracer to examine whether the observed energetic particle deep penetration, especially the differences between electron and proton penetration, can be explained by the transport of inner magnetospheric populations by the modeled electric field of RCM-E.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.