The Major Pathways of the Plasma Sheet Electrons Precipitated in the Regions of Diffuse Aurora

Abstract:

The precipitation of high-energy magnetospheric electrons (E ~ 600eV – 10 KeV) in the diffuse aurora contributes
significant energy flux into the Earth’s ionosphere. It has been found (Khazanov et al. [2014, 2015]) that in order
to fully understand the formation of this flux at the upper ionospheric boundary, ~ 700 – 800 km, it is important to
consider the coupled ionosphere-magnetosphere system. In the diffuse aurora, precipitating electrons initially injected
from the plasma sheet via wave-particle interaction processes degrade in the atmosphere toward lower energies and
produce secondary electrons via impact ionization of the neutral atmosphere. These initially precipitating electrons
of magnetospheric origin can be additionally reflected back into the magnetosphere by the two magnetically
conjugated atmospheres, leading to a series of multiple reflections that can greatly influence the initially precipitating
flux at the upper ionospheric boundary (700-800 km) and the resultant population of secondary electrons and electrons
cascading toward lower energies. In this talk we present the solution of the Boltzman-Landau kinetic equation that
 uniformly describes the entire electron distribution function in the diffuse aurora, including the affiliated production
of secondary electrons (E < 600eV) and their energy interplay in the magnetosphere and two conjugated ionospheres.
This solution takes into account, for the first time, formation electron distribution function in the region of diffuse
aurora starting with the primary injection of plasma sheet electrons via both electron cyclotron harmonic waves and
whistler mode chorus waves to the loss cone, and their follow up multiple atmospheric reflections in the two magnetically
conjugated ionospheres. It is demonstrated that magnetosphere-ionosphere coupling is the key element in the formation
of electron distribution function in the region of diffuse aurora.