The Formation of Electron Heat Flux in the Region of Diffuse Aurora

Abstract

Whistler and electrostatic electron cyclotron harmonics waves are responsible for scattering and precipitating the energetic plasma sheet electrons that drive the diffuse aurora. These primary electrons with energies in the kiloelectron volt range, simultaneously precipitating in magnetically conjugate regions, produce the secondary electron population and can be reflected by the atmosphere back through the magnetosphere and precipitate into the conjugate region with additional follow‐up atmospheric backscatter. Primary, degraded, and secondary electrons can be trapped back into the magnetosphere as they travel back and forth between the two magnetically conjugate ionospheres and continuously delivering their energy to the cold plasma sheet electrons and form the electron thermal fluxes that deposit this energy at the upper ionospheric altitudes. We consider the formation of these heat fluxes focusing on the magnetosphere‐ionosphere energy interplay of the entire superthermal electron spectra from 1 eV up to 10 keV and discuss the efficiency of the different spectral energy intervals that contribute to the electron plasma heating at the magnetospheric altitudes. Our parametric studies at L = 6.8, with lower and upper band chorus whistler wave amplitudes of 10 pT and electron cyclotron harmonic wave amplitudes of 1 mVm−1, indicate the dominant role of the whistler mode in the formation of the electron heat flux coming from the magnetosphere to the ionosphere.

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

“…We find that the geomagnetic trap region, below the AAR, presented in Figure 1 by yellow color, is the main one responsible for the generation of the electron heat flux above s i . This is in agreement with our prior analysis on closed field lines when the heating source of the magnetospheric cold electrons was ionospheric photoelectrons (Section 5.5 in Khazanov (2010), or precipitating electrons in the region of diffuse aurora (Khazanov et al, 2020). This conclusion is also valid on the open magnetic field lines, in the presence of the electrostatic potential jumps in the polar cap region , and emphasizes the important role of the Coulomb collisional diffusion (the second term in 3) in the formation of electron heat fluxes at the magnetospheric altitudes on the global scale.…”

“…The quantitative analysis of above described scenario is based on the STET model developed by Khazanov (2010) and used in the recent studies for the different space plasma applications (Glocer et al, 2017;Khazanov et al, 2018. Following Khazanov et al (2020), the kinetic equation for SE below the AAR region can be presented as KHAZANOV ET AL.…”

Magnetosphere‐Ionosphere Coupling of Precipitated Electrons in Diffuse Aurora Driven by Time Domain Structures

“…Figure 1j shows the simulation scenario that we used in this letter. Compared to our previous similar qualitative plots (Khazanov et al., 2017, 2020), here electron precipitation in the magnetosphere is driven by TDSs on the nightside of the magnetosphere.…”

The Precipitated Electrons in the Region of Diffuse Aurora Driven by Ionosphere‐Thermosphere Collisional Processes

“…The details of STET code implementation in the region of diffuse aurora driven by WPI processes can be found in the papers by Khazanov at al. (2015, 2017, 2020) and will not be repeated here. The only difference here, based on the purpose of this paper, is the E min parameter (fixed in prior studies but variable here), and the usage of only whistler waves as the driving mechanism of electron precipitation in diffuse aurora at L = 6.5 (Meredith et al., 2009; Ni, Thorne, Horne, et al., 2011; Ni, Thorne, Meredith, et al., 2011; Thorne et al., 2010) with parameters of upper band chorus (UBC) and lower band chorus (LBC) waves as presented by Khazanov at al.…”