Abstract
Abstract. A total of 10 radars from the Super Dual Auroral Radar Network (SuperDARN) in Antarctica were used to estimate the spatial area over which energetic electron precipitation (EEP) impacts the D-region ionosphere during pulsating aurora (PsA) events. We use an all-sky camera (ASC) located at Syowa Station to confirm the presence of optical PsAs, and then we use the SuperDARN radars to detect high frequency (HF) radio attenuation caused by enhanced ionisation in the D-region ionosphere. The HF radio attenuation was identified visually by examining quick-look plots of the background HF radio noise and backscatter power from each radar. The EEP impact area was determined for 74 PsA events. Approximately one-third of these events have an EEP impact area that covers at least 12∘ of magnetic latitude, and three-quarters cover at least 4∘ of magnetic latitude. At the equatorward edge of the auroral oval, 44 % of events have a magnetic local time extent of at least 7 h, but this reduces to 17 % at the poleward edge. We use these results to estimate the average size of the EEP impact area during PsAs, which could be used as a model input for determining the impact of PsA-related EEP on the atmospheric chemistry.
Highlights
Pulsating aurorae (PsAs) are diffuse auroral emissions which exhibit quasi-periodic brightness fluctuations of about 2–20 s (Lessard, 2012; Nishimura et al, 2020)
For the Syowa East (SYE) radar, five of these events included some evidence of high frequency (HF) attenuation, but this signature was less clear compared to the other events
Based on the results described above, we can make a rough estimate of the average electron precipitation (EEP) impact area that could be used as input to an atmospheric model such as Whole Atmosphere Community Climate Model (WACCM) (Marsh et al, 2007; Verronen et al, 2016)
Summary
Pulsating aurorae (PsAs) are diffuse auroral emissions which exhibit quasi-periodic brightness fluctuations of about 2–20 s (Lessard, 2012; Nishimura et al, 2020). PsA-related electron density enhancements have been observed at altitudes as low as 68 km, corresponding to electron energies of at least 200 keV (Miyoshi et al, 2015; Turunen et al, 2016; Tesema et al, 2020a) Due to their high occurrence rates, PsAs are thought to be a significant source of ionisation in the upper mesosphere/lower thermosphere region at high latitudes. Tesema et al (2020a) used the 1D Sodankylä ion-neutral chemistry model (Verronen et al, 2005; Turunen et al, 2009) to show that a typical PsA energy spectrum applied for 120 min causes mesospheric oddoxygen depletion of 69 % This significant chemical response indicates that PsA-related EEP may need to be included in atmospheric/climate models, such as the Whole Atmosphere Community Climate Model (WACCM) (Marsh et al, 2007), to properly capture the long-term impact of EEP on natural climate variability.
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