Joule heating at high latitudes

High latitude Joule heating has been calculated from simultaneous observations of the electric field magnitude and the Pedersen conductivity calculated from individual measurements of the ion drift velocity and particle precipitation observed over the lifetime of the AE-C satellite. The data were sorted by latitude, local time, hemisphere, season, and Kp index and separate averages of the electric field magnitude, Pedersen conductivity and Joule heating were prepared. Conductivities produced by an averaged seasonal solar illumination were included with those calculated from the particle precipitation. We found that high-latitude Joule heating occurs in a roughly oval pattern and consists of three distinct heating regions: the dayside cleft, the region of sunward convection at dawn and dusk, and the midnight sector. On the average, heating in the cleft and dawn-dusk regions contributes the largest heat input. There is no apparent difference between hemispheres for similar seasons. Hemisphere averaged Joule heating at equinox amounts to approximately 25 GW for Kp = 1 conditions, 85 GW for Kp = 4, and varies linearly as a function of Kp. The Joule heat input is 50% greater during the summer than during winter primarily due to the increased conductivity caused by solar production.

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