Accurately characterizing the importance of wave-particle interactions in radiation belt dynamics: The pitfalls of statistical wave representations.

Kyle R Murphy,I Jonathan Rae,David G Sibeck,Clare E J Watt,Ian R Mann

doi:10.1002/2016ja022618

Abstract

Wave‐particle interactions play a crucial role in energetic particle dynamics in the Earth's radiation belts. However, the relative importance of different wave modes in these dynamics is poorly understood. Typically, this is assessed during geomagnetic storms using statistically averaged empirical wave models as a function of geomagnetic activity in advanced radiation belt simulations. However, statistical averages poorly characterize extreme events such as geomagnetic storms in that storm‐time ultralow frequency wave power is typically larger than that derived over a solar cycle and Kp is a poor proxy for storm‐time wave power.

Highlights

The physical processes controlling the dynamics of the Earth’s radiation belts are a fundamental and poorly understood aspect of magnetospheric physics and space weather
Wave-particle interactions play a fundamental role in radiation belt dynamics driving both radiation belt loss and acceleration
The relative importance of the various wave modes such as ultralow frequency (ULF), very low frequency (VLF), and electromagnetic ion cyclotron (EMIC) waves for driving radiation belt particle dynamics remains an unsolved problem in magnetospheric physics

Summary

Introduction

The physical processes controlling the dynamics of the Earth’s radiation belts are a fundamental and poorly understood aspect of magnetospheric physics and space weather. During extreme conditions such as geomagnetic storms the radiation belts become exceedingly dynamic During these storms the flux of high-energy particles can vary by over 5 orders of magnitude during periods of either rapid electron loss or acceleration. The relative importance of ULF and VLF wave modes in radiation belt dynamics is inferred from the modeled response as compared to in situ observations. This approach is valid if and only if the empirical wave models are an accurate representation of storm-time wave amplitudes and distributions throughout the magnetosphere. We further discuss the impacts this has on the relative importance of magnetospheric waves in radiation belt electron loss and acceleration and suggest a refined approach to quantifying the role of wave-particle interactions in radiation belt dynamics and modeling

ULF Wave Power

Discussion and Summary