Fine‐Scale Structures of STEVE Revealed by 4K Imaging

• Published in: Journal of geophysical research. Space physics 2023-12, Vol.128 (12), p.n/a
• Main Authors: Nishimura, Y., Dyer, A., Donovan, E. F., Angelopoulos, V.
• Format: Article
• Language: English
• Subjects: Cascade flow; Chemical reactions; citizen scientist observations; Drift; Emissions; fine‐scale structure; Imaging; Ionosphere; Reaction time; Shear flow; Spectral analysis; Spectrum analysis; STEVE, SAID and SAPS; substorm; Temporal resolution; THEMIS, DMSP and spectrograph; Thermal emission; Thermosphere; turbulence in the subauroral ionosphere and thermosphere; Upper atmosphere; Velocity; Wavelengths
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2023JA032008

We utilized a 4K imaging to examine properties of fine‐scale structures of Strong Thermal Emission Velocity Enhancement (STEVE) near the magnetic zenith. Its high spatial (0.09 km at 200 km altitude) and temporal (24 Hz) resolution provided unprecedented details of fine‐scale structures in the subauroral ionosphere. Although the STEVE emission was seen as a homogeneous purple/mauve arc in the all‐sky images, the high‐speed imaging revealed that STEVE contained substantial multi‐scale structures. The characteristic wavelength and period were 12.4 ± 7.4 km and 1.4 ± 0.8 s, and they drifted westward at 8.9 ± 0.7 km/s. The speed is comparable to the reported magnitude of the intense subauroral ion drifts (SAID), suggesting that the fine‐scale structures are an optical manifestation of the E × B drift in the intense SAID. A spectral analysis identified multiple peaks at >10, 4, 2, 1.1, and 83, 33, 16, 9, and