资源环境科技发展态势分析平台

Electromagnetic fluctuations associated with various plasma instabilities have been previously identified near dipolarization fronts in Earth's magnetotail. However, the potential effect of these fluctuations on particle distributions and energy conversion is poorly understood. The most important instabilities responsible for electron acceleration and scattering are the whistler instability and the electron firehose instability. Utilizing 10 years of Time History of Events and Macroscale Interactions during Substorms satellite observations, we explore the occurrence probability and intensity of these instabilities near dipolarization fronts, as function of electron anisotropy and plasma beta. Electron temperature anisotropies are well constrained by the marginal stability conditions of the whistler and oblique electron firehose instabilities. In fact, the observed enhancement of magnetic field fluctuations near the instability thresholds provides good evidence for the operation of these instabilities on electrons near fronts. Since the build-up of electron anisotropy is limited by wave-particle interactions, we conclude that such interactions are important enough to affect electron dynamics and energetics.

Plain Language Summar Dipolarization fronts, transient phenomena frequently observed in the magnetotail, are closely related to substorms. Various types of instabilities are known to be present in the vicinity of dipolarization fronts. The effects of these instabilities on particle dynamics, however, are poorly understood. Our work, utilizing 10 years of Time History of Events and Macroscale Interactions during Substorms satellite observations, demonstrates that electron temperature anisotropies are well constrained by the marginal stability conditions of the whistler and oblique electron firehose instabilities. The occurrence probability of these instabilities and enhancement of magnetic and electric field fluctuations near the instability thresholds provide good evidence for the operation of these two wave types in the vicinity of dipolarization fronts. Our results reveal the importance of wave-particle interactions in the magnetotail near dipolarization fronts and potential effects of those interactions on global energy conversion.