First estimation of the suprathermal electron momentum in the upper ionosphere

 

Speaker: Hanane Marif

Abstract

The ionospheric electron population is divided into two groups. The ambient electrons are thermalized. Their energy is usually smaller than one electronvolt. Their densities and temperatures are the usual ones measured by incoherent scatter radars, or modelled by international codes such as IRI. 

There is however a second population called the suprathermal electrons. This one is either due to photoionization or to electron impact between the atmospheric neutral species and the precipitation in at high altitude.In the frame of space weather, it may be the source of plasma scintillation, plasma bulbs....

The suprathermal electron population cannot be measured and had never  been modelled. Its modelling requests the computation of the electrons stationary flux f by solving the Boltzmann transport equation. This flux is multiplied by various powers of the velocity and integrated to obtain the momentums. By integrating f over dv, one deduces the suprathermal electron density. An integration of  v.f dv allows to compute their mean velocity. Higher momentums give access to their temperature and finally to their heat flux.

We demonstrate for the first time the full and rigorous calculation of momentums up to 3, correcting errors that had been made in the literature (which prevented from computing them up to now). 

As two case studies, we focus on high latitude in the auroral oval and low magnetic latitude over Algier.

Date: 5 July 2018

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