Physics
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsm41a1830e&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #SM41A-1830
Physics
[2704] Magnetospheric Physics / Auroral Phenomena, [2721] Magnetospheric Physics / Field-Aligned Currents And Current Systems, [2736] Magnetospheric Physics / Magnetosphere/Ionosphere Interactions, [2744] Magnetospheric Physics / Magnetotail
Scientific paper
The relationship between bursty bulk flows (BBFs) in the magnetospheric tail and the activation of auroral forms is well established from satellite and ground-based observations. Starting from a self-consistent description of BBFs based on a Vlasov equilibrium we provide a quantitative evaluation of the associated auroral effects by using a quasi-stationary magnetosphere-ionosphere (MI) coupling model. The self-consistent BBF model is based on a kinetic description of a 1-D plasma slab moving in background plasma and electromagnetic field. The model considers two exact constants of motion and one adiabatic invariant (the magnetic moment). It solves the coupled Vlasov-Maxwell system of equations in one spatial dimension (perpendicular to the BBFs plasma bulk velocity and the main magnetic field) assuming the BBF is a 1D structure elongated in the direction of the background magnetic field. The BBF model provides the self-consistent profile of Φm, the electric potential, showing the formation of convergent electric fields at the dawnward flank of the Earth-ward oriented BBFs. It has been shown that magnetospheric convergent electric fields drive field-aligned (FA) potential drops, FA currents and electron precipitation and acceleration. A stationary MI coupling model developed for discontinuity-like magnetospheric generators with convergent electric fields developed earlier is adapted to describe the coupling between the BBFs and the auroral ionosphere. The kernel of the MI coupling model is the condition of current continuity at the topside ionosphere, from which we compute the electric potential in the ionosphere for a given Φm. The MI coupling model is based on a Knight-type current-voltage relationship and a height-integrated conductivity model that depends on the energy deposited in the ionosphere by precipitating electrons. We show that the convergent electric field formed at the flanks of the BBF drive a FA potential drop and downward electron acceleration. The model results provide an estimation of the flux of precipitating electrons, FA current density, and the width of the auroral arc and of the FA current sheet associated to BBF. The model also shows the asymmetric formation of upward/downward FA current sheets corresponding to opposite flanks of the BBFs. We discuss the effects on the electrodynamics of the auroral forms for different values of the BBF velocity and electron temperature and make preliminary comparisons with variation trends observed experimentally from ground.
de Keyser J. M.
Echim Marius M.
Roth M. A.
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