Conjugate observation of auroral finger‐like structures by ground‐based all‐sky cameras and THEMIS satellites

Autor: Katsuki Nishi, Kazuo Shiokawa, Dennis Frühauff
Rok vydání: 2017
Předmět:
Zdroj: Journal of Geophysical Research: Space Physics. 122:7291-7306
ISSN: 2169-9402
2169-9380
DOI: 10.1002/2016ja023774
Popis: In this study, we analyze the first conjugate observation of auroral finger-like structures using ground-based all-sky cameras and the THEMIS satellites, and investigated associated physical processes that are a cause of auroral fragmentation into patches. Two events are reported; one is a conjugate event and the other is a nearly conjugate event. The conjugate event was observed at Narsarsuaq (magnetic latitude: 65.3° N), Greenland, at 0720–0820 UT (0506–0606 LT) on 17 February 2012. Analysis of the event revealed the following observational facts: 1) variation of parallel electron energy fluxes observed by THEMIS-E shows a correspondence to the auroral intensity variation; 2) plasma pressure and magnetic pressure fluctuate in anti-phase with time scales of 5–20 min; 3) perpendicular ion velocity is very small (less than 50 km/s). In the latter event, observed at Gakona, Alaska, on 2 February 2008, the THEMIS-D satellite passed across higher latitudes of finger-like structures. The data from THEMIS-D also showed the anti-phase fluctuation between plasma pressure and magnetic pressure and the small perpendicular ion velocity. From these observations, we suggest that the finger-like structures are caused by a pressure-driven instability in the balance of plasma and magnetic pressures in the magnetosphere.
Databáze: OpenAIRE
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