The impact of field-aligned potentials on Jupiter's auroral emission.

摘要

We present a time-independent model of Jupiter's rotationally driven aurora based on torque balance between the ionosphere and magnetosphere which includes the effects of a field-aligned potential and a variable ionospheric Pedersen conductance. The field-aligned potential arises from field-aligned current limitation at high-latitudes and changes the mapping of the electric fields between the ionosphere and the magnetosphere. We apply a Vlasov solution to determine the location and extent of the field-aligned potential drop along the flux tube. The Pedersen conductance is modified by precipitating auroral electrons. We find a function for the Pedersen conductance that varies with electron precipitation energy and incident energy flux. The primary effect of the field-aligned potential is to enhance the currents transferring angular momentum from the ionosphere to the magnetosphere. Our model reproduces many of the characteristics of Jupiter's main auroral emission derived from observations including the energy flux into the ionosphere (2 - 30 mW/m 2), the width of the aurora at the ionosphere (1000 km), the mapped equatorial location of the aurora (20 - 30 RJ), and field-aligned potentials consistent with observed electron energies (30 - 200 kV).We explore parameter space to show how the auroral current system varies with the radial mass transport rate of the magnetospheric plasma, background ionospheric Pedersen conductance, efficiency of the enhancement in Pedersen conductance, high-latitude electron density, high-latitude electron temperature, location of the acceleration region, and distension of the equatorial magnetic field. Lastly, we explore future extensions of the model within the jovian system and applications to other systems.