Statistical Study of Electron Density Enhancements in the Ionospheric F Region Associated With Pulsating Auroras

Abstract

When a substorm occurs, various plasma waves are excited in the inner magnetosphere by temperature anisotropies and loss cone distribution of the plasma injected from the magnetospheric tail. Immediately after auroral breakups, auroras start to blink quasi-periodically on a time scale of a few seconds to tens of seconds (Yamamoto, 1988). These auroras, called pulsating auroras (PsAs), are believed to be driven by precipitating electrons of energies from a few kiloelectron volts (keV) to tens of keV that are scattered into a loss cone through cyclotron resonance with lower band chorus (LBC) waves near the magnetic equator (e.g., Kasahara et al., 2019Kasahara et al., , 2018Nishimura et al., 2010).Electron precipitation of energies from tens of eV to a few keV associated with PsAs was observed by sounding rockets and low-altitude satellites accompanied by energetic electron precipitation (e.g.,

Theoretical Study of Interhemispheric Electron Bouncing Within Pulsating Aurora

“…This is consistent with statistical observations reported by Fukizawa et al. (2021) where they found electron density enhancements in the F‐region associated with most pulsating auroral events and that nearly 90% of those observed were high enough in altitude that they would correspond to electrons that are less than 100 eV in energy. This is further evidence that secondary electrons of ionospheric origin are bouncing between the hemispheres in regions of pulsating aurora.…”

“…The calculated energy spectra that are shown below correspond to the electron fluxes entering the upper ionospheric altitude of 800 km and include the electrons of ionospheric origin, secondary electrons, that are created via impact ionization in both magnetically conjugate regions. This is consistent with statistical observations reported by Fukizawa et al (2021) where they found electron density enhancements in the F-region associated with most pulsating auroral events and that nearly 90% of those observed were high enough in altitude that they would correspond to electrons that are less than 100 eV in energy. This is further evidence that secondary electrons of ionospheric origin are bouncing between the hemispheres in regions of pulsating aurora.…”