Convective Growth of Auroral Arcs Through the Feedback Instability in a Dipole Geometry

Abstract

Auroral dynamics in the magnetosphere-ionosphere (M-I) coupling system with the dipole magnetic field is investigated by means of a novel simulation code developed with flux coordinates where a set of the reduced magnetohydrodynamic (MHD) and the two-fluid equations for the M-I coupling system is numerically solved. The linear simulations of the feedback instability reveal that a wave packet of auroral arcs propagating in the north-south direction is amplified through the feedback instability, and that the convective growth of auroral structures with enhancement of the ionospheric density and the field aligned current ceases because of the latitudinal dependence of the field line length. These properties are elucidated in terms of the local dispersion relation of the feedback instability for fixed real frequencies.