Effects of the seasonal asymmetry in magnetospheric thermal density distribution and ionospheric conductance on the rate of energy deposition into auroral ionosphere

Details Effects of the seasonal asymmetry in magnetospheric thermal density distribution and ionospheric conductance on the rate of energy deposition into auroral ionosphere Effects of the seasonal asymmetry in magnetospheric thermal density distribution and ionospheric conductance on the rate of energy deposition into auroral ionosphere

Dec 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003agufmsm41b0574p&link_type=abstract

American Geophysical Union, Fall Meeting 2003, abstract #SM41B-0574

Physics

2704 Auroral Phenomena (2407), 2736 Magnetosphere/Ionosphere Interactions, 2752 Mhd Waves And Instabilities, 2753 Numerical Modeling

Scientific paper

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 Alfvén dynamics in the magnetosphere. Effects of plasma anomalous resistivity and Alfvén 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.

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