Mesoscale high‐latitude electric fields are known to deposit energy into the ionospheric and thermospheric system, yet the energy deposition process is not fully understood. We conduct a case study to quantify the energy deposition from mesoscale high‐latitude electric fields to the thermosphere. For the investigation, we obtain the high‐latitude electric field with mesoscale variabilities from Poker Flat Incoherent Scatter Radar measurements during a moderate geomagnetic storm, providing the driver for the Global Ionosphere and Thermosphere Model (GITM) via the High‐latitude Input for Mesoscale Electrodynamics framework. The HIME‐GITM simulation is compared with GITM simulations driven by the large‐scale electric field from the Weimer model. Our modeling results indicate that the mesoscale electric field modifies the thermospheric energy budget primarily through enhancing the Joule heating. Specifically, in the local high‐latitude region of interest, the mesoscale electric field enhances the Joule heating by up to five times. The resulting neutral temperature enhancement can reach up to 50 K above 200 km altitude. Significant increase in the neutral density above 250 km altitude and in the neutral wind speed are found in the local region as well, lagging a few minutes after the Joule heating enhancement. We demonstrate that the energy deposited by the mesoscale electric field transfers primarily to the gravitational potential energy in the thermosphere.
In this study, field‐aligned currents (FACs) and ionospheric electric fields on different spatial scales are investigated through the analysis of FAC data from the Swarm satellites and electric field data from the Dynamic Explorer 2, respectively, from all seasons and under all solar wind conditions and varying levels of solar activity. Distributions of the average and variable components of FAC and electric field are the main focuses of this study, where the FAC variability is represented by the standard deviation of FAC in each magnetic latitude/magnetic local time bin and electric field variability is represented by the square root of the sum of squares of standard deviations of magnetic eastward and equatorward components of the electric field. We found that the mean patterns of the FAC and electric field are mainly contributed by the large‐scale (wavelength: ⩾500 km) FAC and electric field. Unlike the average, in addition to the large scale, variabilities of FAC and electric field are not negligible on mesoscale (wavelength: 100–500 km) and small scale (wavelength: 8–100 km), while the FAC variability shows a different scale dependence from the electric field variability. Specifically, for decreasing scale sizes, the FAC variability increases while the electric field variability decreases, suggesting that the strong FACs on small scale and mesoscale do not necessarily correspond to strong ionospheric electric fields on those scales. Further, FAC variabilities on large scale and mesoscale are included into the Global Ionosphere Thermosphere Model (GITM) and the corresponding impacts on Joule heating have been assessed. It was found that, for the conditions studied here, the large‐scale FAC variability may significantly increase the Joule heating (~160% globally) and that the enhancement due to the mesoscale FAC variability is not negligible (~36% globally).
more » « less- PAR ID:
- 10375238
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 124
- Issue:
- 5
- ISSN:
- 2169-9380
- Page Range / eLocation ID:
- p. 3532-3542
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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