Relationship Between Alfvénic Aurora and Large-Scale Convection and Currents

Details Relationship Between Alfvénic Aurora and Large-Scale Convection and Currents Relationship Between Alfvénic Aurora and Large-Scale Convection and Currents

Dec 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003agufmsm21c..04l&link_type=abstract

American Geophysical Union, Fall Meeting 2003, abstract #SM21C-04

Other

2704 Auroral Phenomena (2407), 2736 Magnetosphere/Ionosphere Interactions, 2752 Mhd Waves And Instabilities, 7827 Kinetic And Mhd Theory

Scientific paper

While Alfvén-wave-induced electron precipitation and fluctuations are prevalent near the polar cap boundary and in the cusp, where the field-aligned currents tend to be irregular, isolated Alfvénic arcs also form within slowly varying, large-scale regions of convection and field-aligned current. Is the occurrence of these isolated Alfvénic arcs regulated by magnetotail processes or M-I coupling? Observations and theory show that the ionospheric conductivity becomes severely depleted in regions of downward field-aligned current while the associated Pedersen electric field is simultaneously enhanced. This situation creates conditions favorable to feedback instability, which develops on a time scale of a few minutes or less and releases energy into ionospheric Alfvén resonator oscillations that would otherwise flow into ionospheric Joule dissipation. Using numerical simulations based on a two-fluid MHD model of magnetospheric Alfvén wave dynamics and E-region ionospheric activity, we have investigated the development of such oscillations in large-scale (of order 100-km), field-aligned current channels. The energetics of these processes are described along with diagnostics that illustrate measurements of the effect by a low-altitude, polar-orbiting satellite. Modulation of electron precipitation by IAR oscillations is also discussed.

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