Long-term variation of Joule heating rates at high latitudes using measurements from PFISR radar

Abstract:

Electromagnetic energy is mainly dissipated in the form of Joule heating in the auroral E-region, which is an important pathway through which energy is transferred in the magnetosphere-ionosphere-thermosphere (MIT) system. It has also been established in many incoherent scatter radar (ISR) investigations that dissipation of energy is modulated by structured neutral winds in the E-region. Previous studies of Joule heating derived from ISR measurements have quantified MLT variations and altitudinal distribution of Joule heating rates. However, previous statistical investigations from ISRs are composed of a relatively small set of data that are irregularly sampled over the past 30 years. A statistical study using a large, regularly sampled, dataset is necessary to understand the long-term variations of Joule heating under different geophysical conditions.

We present results from a nearly continuous set of observations made by the Poker Flat Incoherent Scatter Radar (PFISR), located near Fairbanks, AK, USA. We undertook a statistical study of Joule heating rates using a dataset from 2010-2017 in which we examined the seasonal and solar cycle dependence of Joule heating rates, including the effects of neutral winds. Specifically, we subdivided our results using the AE index into geomagnetically active and quiet intervals. We made a comparison of our results relative to previous ISR investigations. This study is the first to investigate Joule heating rates by taking advantage of the AMISR radar system at Poker Flat and will contribute to the understanding of the long-term variation of energy transfer in the high latitude Ionosphere-thermosphere system.