2011 SuperDARN Workshop       

High-latitude convection maps derived from AMPERE field-aligned currents and comparisons with SuperDARN line-of-sight velocities

V.G. Merkin, B.J. Anderson, E.R. Talaat, R.J. Barnes
The Johns Hopkins University Applied Physics Laboratory, USA

abstract. We present preliminary results from a procedure reconstructing high-latitude ionospheric convection from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) field-aligned currents. The basis for the procedure is the solution of the ionospheric Ohm's law derived from current continuity. Three models of ionospheric conductance are used: an empirical model of Extreme Ultraviolet (EUV) ionization; the above with particle precipitation added; and the third where the conductance is modified by anomalous electron heating resulting from Farley-Buneman instability. The precipitation model used includes two contributions: the diffuse aurora is determined from a plasma sheet specification obtained from a global magnetospheric simulation; and the discrete aurora is obtained from the AMPERE currents through the Knight relation. The Farley-Buneman turbulence contribution results in conductances amplified by a factor roughly proportional to the local convection electric field. Once the ionospheric conductance tensor is determined, it is used, along with the AMPERE currents, to derive the ionospheric potential and corresponding electric fields and convection velocities. The latter are compared with SuperDARN line-of-sight velocities. Generally, very good agreement is observed between AMPERE-inferred and SuperDARN velocities, but the result, not-surprisingly, depends strongly on the conductance magnitude and gradients. We discuss similarities and discrepancies between AMPERE and SuperDARN velocities and demonstrate how strong a constraint the superposition of the two provides on the possible conductance distributions. This suggests that such techniques, combined with other ionospheric electrodynamics measurements, are feasible for reconstruction of realistic conductance distributions.

Sakaguchi KaoriNICT Japan