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

Abstract

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.

Variability in the Electrodynamics of the Small Scale Auroral Arc

“…(2020) and later expanded upon by Krcelic et al. (2023). Full details can be found in previous papers, but a brief description is provided here.…”

“…In the present study we conclude that there is a relation between the two, which should be investigated further. An empirical formula linking these two parameters would be useful, since estimates of the variability of small scale electric fields are the key for precise estimates of intense local Joule heating (Kavanagh et al., 2022; Krcelic et al., 2023).…”

“…In order to model the O + emissions we use the method initially developed by Tuttle et al (2020) and later expanded upon by Krcelic et al (2023). Full details can be found in previous papers, but a brief description is provided here.…”

Dissipation Rates of Mesospheric Stratified Turbulence From Multistatic Meteor‐Radar Observations

“…Rocket launch decisions might be made on specific conditions, for example, based on radar monitoring of the presence of polar mesospheric summer echoes. Incoherent scatter measurements of the ionospheric D‐region require auroral precipitation, which is associated with large electric fields and Joule heating (Krcelic et al., 2023) and could affect the measurements of dissipation rates.…”

In Praise of the Unexpected

“…The original idea to solve the continuity equation for the O + ions is a complex problem, with ion velocity as a free parameter. The results give the dynamic changes of the ion population in the 3D volume around the magnetic zenith (Krcelic et al., 2023; Tuttle et al., 2020). By combining these results with HiTIES spectral measurements, the temperature of the ionosphere can be estimated and compared with the changes in electric fields, which is another strand in the search to understand the role of the small‐scale aurora in heating the atmosphere.…”