Paper#: 102
Poster #:
Session Name: Workshop 1A: High Latitude Processing
Room: West Ballroom
Day: Monday
Time: 11:40-Noon
Abstract Title: Simulation of Discrete Auroral Arcs
PresentSurname: Evans, D.S.
All Authors: D.S. Evans, J. Lemaire, V. Pierrard, M. Roth , J. Dekeyser
Abstract : The origin of the Electromotive Force responsible for field aligned currents in auroral arcs can be the electrostatic potential difference existing at the interface between an earthward moving hot plasmasheet cloud, containing energetic electrons and ions, and the colder plasma in the plasma through. This thermoelectric potential difference results from electronic pressure gradients and velocity shears across the interface boundary/sheath between the hot and cold plasma regions. The presence of the boundary between the two plasma populations also modifies the distribution of any large scale externally applied potential difference so as to concentrate that potential difference at the boundary and increasing the available EMF. This transverse electric potential difference, produced at high altitude, is distributed both along geomagnetic field lines down into the auroral ionosphere and transverse to the magnetic field in the ionosphere; that portion distributed along the magnetic field lines may appear as multiple double layers (DL). The parallel electric potential distribution V(h) of this chain of DLs is modeled by solving Poisson's equation for exospheric models that describe self-consistently the density distributions of the mixed cold-ionospheric and hot-magnetospheric plasmas (Lemaire et al., 2002). A new collisionless (kinetic) model is used to calculate the source EMF, namely thermoelectric potential distribution V(L) across the surface of high altitude plasma cloud which is assumed to be a collisionless tangential discontinuity (Dekeyser et al., 2002). The width of auroral arcs as well as the altitudes of the DLs are modeled for a variety of boundary conditions using typical high and low altitude plasma densities, temperature, and velocity shears.