GEM: Suprathermal and Energetic Ion Heating by Electromagnetic Ion Cyclotron Waves and Magnetosonic Waves in the Inner Magnetosphere

Trustees Of Boston University, Boston

Investigators

Abstract

The focus of this project is to study the ion heating by plasma waves in the Earth's magnetosphere. The electromagnetic ion cyclotron (EMIC) and magnetosonic waves are plasma waves generated by ring current ions in the magnetosphere. These plasma waves could scatter and heat the ions, transferring energy from the ring current to other regions or populations. This project investigates the ion heating process by combining simulations with Van Allen Probes observations. The modeling efforts will reveal the source of ions from wave-particle interaction. Understanding the ion dynamics will help future space missions traveling through the magnetosphere and implementation of the ion-wave interaction effects in space weather prediction. This project will help quantify the ion flux variations in the inner magnetosphere, where many satellites are operating to provide human's essential needs of communication, navigation, and security. This project supports two early-career scientists, a female faculty and a graduate student at Boston University. The Center for Space Physics at Boston University provides an ideal environment for collaboration in space science research, student training and teaching, community engagement, and outreach activities. This project aims to determine the conditions and consequences of resonant ion heating by EMIC and magnetosonic waves through comprehensive satellite observations and numerical modeling. Firstly, a survey of ion heating events will be performed using the Van Allen Probes data. The ion heating events will be categorized by different wave properties and background plasma parameters, to reveal the critical conditions that cause evident ion heating features in the inner magnetosphere. Secondly, a series of quasilinear simulations of the ion heating and scattering effects will be performed during the EMIC and magnetosonic wave events. The simulation inputs are provided by the wave properties and background plasma parameters from the survey to demonstrate the efficiency and energies of ion heating. Thirdly, since the amplitudes of EMIC and magnetosonic waves could be large so that they can break the quasi-linear approximation, the interaction between ions and large amplitude waves will be evaluated using a test particle code. A series of test particle simulations will be performed through varying wave amplitudes to find the threshold beyond which nonlinear effects become important. The ion phase trapping and bunching effects by strong EMIC and magnetosonic waves will also be evaluated to quantify their contribution to ion acceleration at different energies. 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.