Seminars

Lecturer: Bengt E. Eliasson (Bochum)
Date: 2011-12-20 10:30
Place: Aniara

Full-scale simulations of ionospheric turbulence

Bengt E. Eliasson
Institute for Theoretical Physics
Faculty of Astronomy and Physics
Ruhr-University Bochum
Germany

Abstract
Large amplitude electromagnetic
waves in the megahertz range can excite electrostatic turbulence
and low-frequency waves and structures in the kilohertz range in the ionosphere.
While the electromagnetic waves have wavelengths of the order
100 meters, the electrostatic waves and nonlinear structures have
wavelengths below one meter, which makes full-scale numerical
simulations challenging. A full-scale numerical scheme
must resolve these two length- and times-scales, as well as
the ionospheric profile which is on 100 km length-scale.
To overcome severe limitations on the timestep and computational
load, a nested grid method is devised, in which the electromagnetic
wave is represented on a coarser grid with a spacing of a few meters
and the electrostatic waves and the evolution equations for the particles
are resolved on a denser grid of a few centimenters locally in space.
In this manner, the computational load is decreased drastically and
a factor 100 longer timesteps can be taken, which makes it possible to perform
full-scale simulations that cover the different time- and space-scales
mentioned above. We discuss these simulations and how they are
used to study turbulence, stimulated electromagnetic radiation
and particle acceleration and heating by the ionospheric turbulence.


Created 2011-11-14 10:10:19 by Mats Holmström
Last changed 2011-12-19 09:01:11 by Mats Holmström