The Electrodynamic, Thermal, and Energetic Character of Intense Sun- Aligned Arcs in the Polar Cap
PHILLIPS LAB HANSCOM AFB MA
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The electrodynamic, thermal and energetic character of stable Sun- aligned arcs in the polar cup can be meaningfully diagnosed by an incoherent scatter radar, provided a suitable observing scheme is selected. We report here such measurements of two intense Sun-aligned arcs. The two arcs were diagnosed on two different nights February 26 and March 1, 1987 using the Sondre Stomfjord radar as a stand-alone diagnostic. Repeatable patterns are found in mesoscale area maps of altitude profiles for observed electron and ion gas number densities, temperatures, and line-of-sight velocities, and projected mesoscale area maps of derived electric fields, Pedersen and Hall conductivities, horizontal and field-aligned currents, joule heating rate, and Poynting flux. We confirm, for the first time with continuous mesoscale area maps, that the arcs have the anticipated simple are electrodynamics. That is, the visual and enhanced ionization signatures of the arc are produced by incoming energetic electrons carrying the outgoing current from the electric field convergence in the arc.
- Atmospheric Physics