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

Abstract

During periods of intense geomagnetic activity, strong DC electric fields, 𝐴𝐴 ⃖⃖ ⃗ 𝐸𝐸0 , perpendicular to the geomagnetic field, 𝐴𝐴 ⃖⃖ ⃗ 𝐵𝐵 , penetrate from the Earth's magnetosphere into the high-latitude ionosphere where they dissipate energy, form electrojets, and drive plasma instabilities in the E-region ionosphere, at altitudes roughly between 90 and 130 km. In the global picture of magnetosphere-ionosphere coupling, this is the region where most of the field-aligned magnetospheric currents close. E-region instabilities generate plasma density irregularities, typically within the wavelength range from tens of centimeters to tens of meters, coupled with wavelike electrostatic field fluctuations. The density irregularities have been routinely detected as strong coherent radar echoes (e.g.,

The Distribution of Small‐Scale Irregularities in the E‐Region, and Its Tendency to Match the Spectrum of Field‐Aligned Current Structures in the F‐Region

“…An explanation in the context of recent work by Dimant et al. (2021) involves high‐energy electrons. Increases in high‐energy electron precipitation should normally be accompanied by conductivity enhancements brought about by the turbulence created by charge deposition at impact altitudes near 120 km.…”

“…But the electric field pattern would still match the source pattern, that is, the shape of the precipitation field in directions perpendicular to the magnetic field. An explanation in the context of recent work by Dimant et al (2021) involves high-energy electrons. Increases in high-energy electron precipitation should normally be accompanied by conductivity enhancements brought about by the turbulence created by charge deposition at impact altitudes near 120 km.…”

Investigation of Ionospheric Small‐Scale Plasma Structures Associated With Particle Precipitation

“…Dimant et al. (2021) note that energetic electrons reaching the E‐region ionosphere can modify the instability threshold of the Farley‐Buneman type of instabilities. Without precipitation, strong electric fields, which are mapped down from the magnetosphere, can drive E‐region instabilities, which further lead to plasma turbulence and increased conductance.…”

The future of auroral E-region plasma turbulence research

“…The E-region coherent scatter is instead observed at the boundaries of these very enhanced plasma density regions. The reduction in E-region coherent scatter has been attributed to either a suprathermal electron population that suppresses plasma instability growth (Dimant et al, 2021), or a suppression of the electric field strength from enhanced conductivity due to higher plasma densities in the region (e.g., Maynard et al, 1973). The location of the plasma turbulence with respect to other ionospheric phenomena can provide information on the ionospheric characteristics in the region to aid in investigating the turbulence.…”