Collaborative Research: GEM--Radiation Belt Losses Using Combined Global Hybrid and Test Particle Simulations

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). The radiation belts around the Earth consist mainly of relativistic particles that are trapped from the solar wind and cosmic rays. This region of space is extremely dynamic.

In the inner magnetosphere, the part of the radiation belts closer to Earth, ultra-low frequency (ULF) waves play important roles in the acceleration and loss of particles. This project will investigate these processes with 3-D hybrid simulations combined with test-particle electron calculations, guided by multipoint space observations. Results will have broad application to understanding magnetospheres of the Earth and other planets. The work supports a Ph.D. student and two undergraduate students.

The project will establish the role of ULF waves, including electromagnetic ion cyclotron (EMIC) waves and kinetic Alfven waves (KAWs), in the radiation belt electron loss as well as electron radial diffusion. The science questions that will be answered include: (1) What internal or external processes control the generation and global structure, including ion wave-particle interactions, of EMIC waves and KAWs in the inner magnetosphere?

How are EMIC/Alfven waves excited by localized injections from the tail or external compressions? (2) What are the transport coefficients of energetic electrons in these EMIC waves and KAWs, and what are the associated electron scattering and precipitation into the loss cone? (3) What are the effects of ULF waves and external compressional pulses on electron radial transport? The team will conduct relativistic test-particle electron calculations in 3-D global hybrid simulations.

The hybrid models, describing fully kinetic ion physics, include an inner magnetospheric hybrid model in dipole geometry and the Auburn global hybrid code in 3-D (ANGIE3D) based on the self-consistent solar wind-magnetosphere interaction. The simulations will be validated with observations of the near-equatorial measurements from NOAA and NASA operated satellites and low-altitude measurements from satellites, CubeSats, and balloon experiments.

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.