Electron Energy Interplay in the Geomagnetic Trap Below the Auroral Acceleration Region

Abstract

This publication addresses the collisional superthermal electron dynamics below the auroral acceleration region (AAR). This region is the portion of an auroral field line with a field‐aligned electric field that leads to the formation of precipitating monoenergetic keV electron fluxes that produce the discrete auroral displays observable from the ground. It is assumed that these precipitating electron fluxes are monoenergetic and accelerated through a potential drop, V, such that these electrons are peaked at an energy E0 = eV, where e is the electron charge. Monoenergetic electrons precipitating into the upper atmosphere degrade to lower energies via many different collisional processes and produce the secondary electron population with energies of 10–100s eV which escapes back to magnetospheric altitudes and becomes geomagnetically trapped between the AAR and the upper ionosphere. The secondary electrons in this geomagnetic trap transfer energy via elastic Coulomb collisions to the thermal electrons. That energy is then returned to the topside ionosphere as heat flux carried by the electron thermal conduction which is essential to maintaining the topside electron temperature.

A 2D Kaleidoscope of Electron Heat Fluxes Driven by Auroral Electron Precipitation

“…A future work will utilize the actual time-variable energy fluxes and mean energies provided for these time windows by THEMIS ASI. We then calculate the electron heat flux using the relations presented in Section 3, based on the publications of Khazanov et al (2020Khazanov et al ( , 2021a. As in Gabrielse et al (2021), the data in Figures 2 and 3 use assumptions regarding the distribution function of precipitating electrons: Gaussian (Figure 2) and Maxwellian (Figure 3).…”

“…Both afore mentioned studies have been validated. The STET model has been validated with DMSP (Khazanov et al (2021a) and FAST (Khazanov et al, 2016) electron spectra measurements as well with optical observation by (Samara et al, 2017). The new technique developed by Gabrielse et al (2021) was independently validated using Poker Flat Incoherent Scatter Radar (PFISR) data.…”

Electron Heat Fluxes Generated by Intense Whistler Waves at the Upper Ionospheric Altitudes

“…STET code solves gyro‐average kinetic equation for the SE for the energies above 1 eV and its upper energy limit is not restricted because it includes the relativistic effects (Khazanov, 2010). This kinetic equation for the SE that we used in our study can be presented as (Khazanov, Glocer, & Chu, 2021) $$$\frac{1}{\mathit{v}}\frac{\partial {\Phi}}{\partial \mathit{t}}\,+\,\mu \frac{\partial {\Phi}}{\partial \mathit{s}}\,-\,\frac{1\,-\,{\mu }^{2}}{2}\left(\frac{1}{\mathit{B}}\frac{\partial \mathit{B}}{\partial \mathit{s}}\,-\,\frac{\mathit{F}}{\mathit{E}}\right)\frac{\partial {\Phi}}{\partial \mu }\,+\,\mathit{E}\mathit{F}\mu \frac{\partial }{\partial \mathit{E}}\left(\frac{{\Phi}}{\mathit{E}}\right)\,=\,\mathit{Q}\,+\,\langle \mathit{S}\rangle $$$ where Φ = 2Ef/m 2 is the SE flux, f is the electron distribution of SE and m their mass, B is geomagnetic field, v is SE velocity, t is time, s is the distance along the field line, E is the particle energy, and μ is the cosine of the pitch‐angle. F is the electric field force, Q is the SE source term from EUV flux, and 〈 S 〉, which includes collision integrals, represents interactions with thermal electrons and ions, scattering with neutral particles, and wave‐particle interactions.…”

Effects of Electron Precipitation on E‐Region Instabilities: Theoretical Analysis

“…The STET setting in the region of monoenergetic aurora is similar, but assumes the existence of an electrostatic acceleration region located at altitudes of (1.5–2) R E (Marklund et al., 2011), where R E is the Earth's radius. Specifically, STET code was set up to run from the northern or southern hemispheres from 90 km to 2 R E with the multiple reflection (backscatter) of the electrons whose electrostatic energies are smaller than the potential drop of the acceleration region (Khazanov et al., 2021).…”