Fine‐Scale Electric Fields and Joule Heating From Observations of the Aurora

Optical measurements from three selected wavelengths have been combined with modeling of emissions from an auroral event to estimate the magnitude and direction of small‐scale electric fields on either side of an auroral arc. The temporal resolution of the estimates is 0.1 s, which is much higher resolution than measurements from Super Dual Auroral Radar Network (SuperDARN) in the same region, with which we compare our estimates. Additionally, we have used the Scanning Doppler Imager instrument to measure the neutral wind during the event in order to calculate the height integrated Joule heating. Joule heating obtained from the small scale electric fields gives larger values (17 ± 11 and 6 ± 9 mWm−2 on average on each side of the arc) than the Joule heating obtained from more conventionally used SuperDARN data (5 mWm−2). This result is significant, because Joule heating will cause changes in the thermosphere from thermal expansion and thermal conductivity, and may also affect the acceleration of the neutral wind. Our result indicates that high spatial and temporal resolution electric fields may play an important role in the dynamics of the magnetosphere‐ionosphere‐thermosphere system. Key Points Small scale electric fields are estimated on both sides of an auroral arc using optical techniques Joule heating is estimated, by combining optical data with neutral wind observations Local, high resolution Joule heating shows much higher values than the Joule heating obtained from more averaged radar measurements