Seminars

Lecturer: Herbert Gunell (BIRA-IASB)
Date: 2016-04-14 10:00
Place: Aniara

Adventures of double layers in the upward and downward current regions of the aurora

Herbert Gunell
Royal Belgian Institute for Space Aeronomy

Abstract:
The auroral current circuit is made up of four elements:
the upward and downward current regions, the ionosphere,
and the magnetically connected magnetospheric counterpart.
In both the upward and downward current regions, double
layers have been observed by satellite based instruments.
In the upward current region, where the electrons are
accelerated into the stronger magnetic field, a steady
state may form, where there is a stable double layer
position at altitudes of about one Earth radius.

In the downward current no stable equilibrium exists, and
instead double layers form at low altitude and move
upward. As the magnetic field decreases with increasing
altitude so does the density of the electrons that have
their source at the ionosphere. The particles that have
their source at the equatorial magnetosphere, on the other
hand, have a constant density. When the double layer moves
upward it eventually reaches an altitude where the density
of the ionospheric electrons is so low that the Langmuir
condition no longer can be maintained. When this happens a
new double layer forms at low altitude and the process
starts over.

In this seminar, these processes are discussed in terms of
an electrostatic Vlasov simulation model.


Created 2016-03-14 10:49:04 by Mats Holmström
Last changed 2016-03-14 11:58:22 by Mats Holmström