HR: 0830h
AN: SM41B-0574    [PDF]
TI: Effects of the seasonal asymmetry in magnetospheric thermal density distribution and ionospheric conductance on the rate of energy deposition into auroral ionosphere
AU: * Pokhotelov, D
EM: Dimitri.Pokhotelov@newcastle.edu.au
AF: School of Mathematical and Physical Sciences, University of Newcastle, University Drive, Callaghan, NSW 2308 Australia
AU: Lotko, W
EM: William.Lotko@dartmouth.edu
AF: Thayer School of Engineering, Dartmouth College, 8000 Cummings Hall, Hanover, HN 03755 United States
AU: Streltsov, A V
EM: Anatoly.Streltsov@dartmouth.edu
AF: Thayer School of Engineering, Dartmouth College, 8000 Cummings Hall, Hanover, HN 03755 United States
AU: Menk, F W
EM: Fred.Menk@newcastle.edu.au
AF: School of Mathematical and Physical Sciences, University of Newcastle, University Drive, Callaghan, NSW 2308 Australia
AU: Waters, C L
EM: Colin.Waters@newcastle.edu.au
AF: School of Mathematical and Physical Sciences, University of Newcastle, University Drive, Callaghan, NSW 2308 Australia
AB: A 2D numerical model of the coupled magnetosphere-ionosphere system has been used to analyze the effects of seasonal variations in thermal plasma density distribution along magnetic flux tube and ionospheric solar-induced Pedersen conductance on the development of ionospheric feedback instability and associated energetic electron precipitation. The numerical model includes a model of the horizontally inhomogeneous auroral ionosphere with conductivity dynamics coupled to a two-fluid MHD model describing dispersive shear Alfv\'{e}n dynamics in the magnetosphere. Effects of plasma anomalous resistivity and Alfv\'{e}n wave dispersion in the magnetospheric MHD model lead to the formation of parallel electric fields above the ionosphere as the feedback instability evolves. The energy deposition rate of energetic electrons is estimated from Fridman-Lemaire theoretical model based on adiabatic motion of loss-cone electrons originating in the equatorial magnetosphere. Due to the seasonal asymmetry in thermal electron density distribution along magnetic field lines and ionospheric Pedersen conductance the rate of kinetic electron energy deposition is significantly greater in the dark winter hemisphere where the thermal plasma density at the auroral acceleration region and solar-induced ionospheric conductance are substantially lower. It is also demonstrated that the asymmetry in thermal density distribution leads to seasonal variations in the altitude of acceleration region, while the asymmetry in ionospheric conductance results in hemispherical asymmetry of field-aligned Poynting flux. The higher energy deposition into the dark ionosphere may increase the occurrence of discrete aurora as been demonstrated by satellite measurements of energetic electron precipitation and UV auroral imaging.
DE: 2704 Auroral phenomena (2407)
DE: 2736 Magnetosphere/ionosphere interactions
DE: 2752 MHD waves and instabilities
DE: 2753 Numerical modeling
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting