High‐latitude Joule heating response to IMF inputs

Abstract

We evaluate the response of the high‐latitude Joule heating to orientation and magnitude of the interplanetary magnetic field (IMF). Approximately 9000 individual Joule heating patterns derived from data assimilation for the northern hemisphere were used to develop averaged and hemispherically integrated Joule power maps for the northern hemisphere north of 40° magnetic latitude. Hemispherically integrated Joule heating increases with IMF magnitude when the IMF is southward, but is relatively unchanged with increased IMF magnitude when the IMF is north. Only a small IMF By effect is evident in the Joule heating patterns. We quantify the IMF effects with linear fits of integrated Joule heating as a function of IMF magnitude for eight different IMF clock angle bins in the GSM Y‐Z plane. During extreme northward IMF conditions, Joule heating is restricted to the high latitude dayside. During extreme southward IMF conditions, Joule heating is located predominantly in the auroral region, with increased heating in the morning sector compared to the evening sector. This additional heating may lead to the increased incidence of gravity waves reported in the morning sector. Our estimate of the increase of hemispherically integrated Joule heating with IMF magnitude during southward IMF periods is 13GW/nT.