[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-07] Observations of Electron Microburst Precipitation With an Inverse Time of Flight Energy Dispersion

*Mykhaylo Shumko¹、Yoshizumi Miyoshi²、Lauren W Blum³、Alexa Jean Halford⁴、Arlo Johnson⁵、John Sample⁶、David Klumpar⁶、Harlan Spence⁵ (1.University of Maryland in College Park、2.Nagoya University、3.University of Colorado in Boulder、4.NASA's Goddard Space Flight Center、5.University of New Hampshire、6.Montana State University in Bozeman)

キーワード：Microbursts, FIREBIRD-II, CubeSat, Chorus waves, Wave-particle interactions

Wave-particle interactions are a ubiquitous phenomenon in plasmas. In Earth's inner magnetosphere, interactions between whistler mode chorus waves and electrons is believed to be one of the dominant mechanisms for both the heating of the outer Van Allen radiation belt electrons, and rapidly precipitating electrons into Earth's atmosphere. One form of this precipitation is called electron microbursts: a sub-second and intense bursts of electrons most often observed by high altitude balloons and low Earth orbiting satellites. Despite years of focused investigations, fundamental details regarding the microburst-chorus scattering mechanism, including the scattering latitude and resonance harmonic, is to this day largely unconstrained. One way to probe these properties is by examining the energy-dependent time of flight dispersion of microburst electrons. If electrons of all energies were scattered at the same magnetic latitude, then the time of flight dispersion would be normal: the low energy electrons would lag behind the higher energy electrons. On the other hand, if the cyclotron resonance is the dominant mode, then the higher energy electrons would resonate at higher magnetic latitudes, leading to a race condition: the higher energy electrons, while moving faster, have further to travel before their impact with the atmosphere. Under certain circumstances this results in inverse time of flight dispersion with lower energy electrons arriving first. Considering this theoretical framework, we present clear evidence of inversely dispersed microbursts observed by the FIREBIRD-II CubeSat mission on 27 August 2015 at 12:40 UT. Our results demonstrate that this dispersion can be observed, and by using it we constrained the chorus wave properties responsible for microburst scattering.