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A Case Study of Connection Between Ground Magnetic Field Perturbations and Tail Current Sheet Bursty Flows at X = −60 R E
Author(s) -
Wang ChihPing,
Xing Xiaoyan,
Liu YiHsin,
Runov Andrei
Publication year - 2018
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2017ja024972
Subject(s) - magnetic field , physics , instability , bubble , plasma sheet , current (fluid) , anisotropy , flow (mathematics) , current sheet , surge , plasma , substorm , amplitude , geophysics , mechanics , magnetohydrodynamics , magnetosphere , meteorology , optics , quantum mechanics , thermodynamics
We report the first observations that connect a burst of fast flows and Pi2 fluctuations in the midtail current sheet at X ~ −60 R E with ground magnetic negative bays and Pi2 pulsations at high latitudes near 70°. Both the flow burst and negative bays occurred around midnight and were isolated and lasted for ~10 min. The flow burst had the characteristics of a low‐density plasma bubble. It was moving earthward at ~340 km/s and was accompanied by field‐aligned currents. The timing and equatorward motion of magnetic bays can be accounted for by this earthward moving bubble. Enhanced Pi2 fluctuations were observed within both the bubble and the magnetic bays. Pressure anisotropy with higher parallel pressure was observed associated with the flow burst and was firehose unstable. We discuss firehose instability as one of the possible mechanisms for the Pi2 fluctuations.