Impact of Precipitating Electrons and Magnetosphere‐Ionosphere Coupling Processes on Ionospheric Conductance

Abstract

Modeling of electrodynamic coupling between the magnetosphere and ionosphere depends on accurate specification of ionospheric conductances produced by auroral electron precipitation. Magnetospheric models determine the plasma properties on magnetic field lines connected to the auroral ionosphere, but the precipitation of energetic particles into the ionosphere is the result of a two-step process. The first step is the initiation of electron precipitation into both magnetic conjugate points from Earth's plasma sheet via wave-particle interactions. The second step consists of the multiple atmospheric reflections of electrons at the two magnetic conjugate points, which produces secondary superthermal electron fluxes. The steady state solution for the precipitating particle fluxes into the ionosphere differs significantly from that calculated based on the originating magnetospheric population predicted by magnetohydrodynamic and ring current kinetic models. Thus, standard techniques for calculating conductances from the mean energy and energy flux of precipitating electrons in model simulations must be modified to account for these additional processes. Here we offer simple parametric relations for calculating Pedersen and Hall height-integrated conductances that include the contributions from superthermal electrons produced by magnetosphere-ionosphere-atmosphere coupling in the auroral regions.Plain Language Summary The magnetosphere and ionosphere are strongly coupled by precipitating electrons during storm times. Therefore, first-principle simulations of precipitating electron fluxes are required to understand storm time variations of ionospheric conductances and related electric fields. As discussed by Khazanov et al. (2015, https://doi.), the first step in such simulations is to initiate electron precipitation into both magnetic conjugate points from the Earth's plasma sheet via wave-particle interaction processes. The second step is to determine the effects of multiple atmospheric reflections on electron fluxes at the boundary between the ionosphere and magnetosphere at the two magnetic conjugate points. Here we offer simple parametric relations for calculating electric Pedersen and Hall height-integrated conductances that include the contributions from superthermal electrons produced by magnetosphere-ionosphere-atmosphere coupling in the auroral regions.

The Magnetosphere‐Ionosphere Electron Precipitation Dynamics and Their Geospace Consequences During the 17 March 2013 Storm

“…The plot of the |E × B| drift speed shows that there are less strong flow channels from~20 to 1 MLT with the STET modifications, but that the SAPS are stronger and extend to lower latitude with the STET modification. As demonstrated in our previous studies (Khazanov et al, 2015(Khazanov et al, -2018, and sections 2 and 3 of this paper, plasma sheet electrons that are scattered into the loss cone by WPI processes and precipitated to the ionosphere lose their energy due to nonelastic collisions with the neutral atmosphere and produce SEs. This also requires further quantitative investigation beyond the scope of this paper.…”

“…As was shown by Khazanov et al (2015Khazanov et al ( -2018, these processes greatly influence the total precipitating flux at the upper ionospheric boundary (around about 800 km). The precipitating and SEs can also reflect back into the magnetosphere and then undergo multiple reflections at the magnetic conjugate points.…”

“…Because the Robinson et al formulae are widely used in the community, Khazanov et al (2018) used STET to provide a simple modification to the Robinson et al formulae for precipitating electron energy flux spectra that do not take into account the multiple reflection process (e.g., from magnetospheric models). However, it is preferable to modify the simulated precipitating electron energy spectra directly, as this would produce a more realistic description of the precipitating electron distribution and account for precipitated electron energy deposition to the neutral atmosphere and ionospheric plasma components.…”

“…However, it is preferable to modify the simulated precipitating electron energy spectra directly, as this would produce a more realistic description of the precipitating electron distribution and account for precipitated electron energy deposition to the neutral atmosphere and ionospheric plasma components. The methodology of modifying the energy fluxes in (2) is quite similar to that discussed by Khazanov et al (2018) for the modification of Pedersen and Hall conductances by accounting for the SE MI coupling processes. The methodology of modifying the energy fluxes in (2) is quite similar to that discussed by Khazanov et al (2018) for the modification of Pedersen and Hall conductances by accounting for the SE MI coupling processes.…”

“…Collisionless processes dominate in the inner magnetosphere, whereas collisional interactions are important in the ionosphere, and Khazanov et al (2018) have emphasized that first-principle simulations of precipitating electron fluxes in both regimes are required to understand spatial and temporal variations of ionospheric conductance and related electric fields. The second step is to account for multiple atmospheric reflections of electrons between the ionosphere and magnetosphere at the two magnetically conjugate points, as treated in the SuperThermal Electron Transport (STET) model (Khazanov et al, 2015(Khazanov et al, , 2017a(Khazanov et al, , 2017b(Khazanov et al, , 2018Khazanov, Himwich, et al, 2016). The second step is to account for multiple atmospheric reflections of electrons between the ionosphere and magnetosphere at the two magnetically conjugate points, as treated in the SuperThermal Electron Transport (STET) model (Khazanov et al, 2015(Khazanov et al, , 2017a(Khazanov et al, , 2017b(Khazanov et al, , 2018Khazanov, Himwich, et al, 2016).…”