Abstract
AbstractWe report the direct observation on bursty bulk flow (BBF) deceleration down‐tail of X < −15 RE by MMS satellite. Two typical events are presented in the paper. In the first event on 05 June 2018, MMS1 is located at X ~ −16.1 RE and records four individual bursty flows (BFs). Each burst flow has distinctly lower velocity than the preceding one. Accompanying with the decelerated BFs, the Bz/Bx continuously increases/decreases. Simultaneous Vx‐decrease and Bz‐increase are in coincidence with the scenario of the local BBF deceleration and formation of the magnetic pileup region. In the second event on 03 July 2017, MMS stays in the neutral sheet of X ~ −24.5 RE, and encounters similar BBF deceleration process. For both events, the decelerated BF series exhibit prominent medium‐energy ion component (2–10 KeV). Analyses show enhanced parallel current (J//) and Kinetic Alfvénic wave (KAW) emitting during the BF intervals. The strength of the emitted KAW has a clear tendency to decay with the BBF decreasing. Power spectra density analysis confirms the substantial Joule dissipation during the BBF deceleration, both J// and J⊥. Combined analyses support BBF dissipation via Joule heating as well as KAW emitting. Finally, we propose a possible mechanism on the BBF deceleration, i.e., “collision” with the tailward flow.
Highlights
IntroductionBursty bulk flows (BBFs) are the most common and significant phenomenon in the Earth's magnetotail (Baumjohann et al, 1990; Baumjohann, 2002; Angelopoulos et al, 1992, 1994; Zhang et al, 2009, 2015, 2015, 2016, 2016)
We report the direct observation on bursty bulk flow (BBF) deceleration down‐tail of
The decelerated BBF is characteristic of the prominent medium‐energy ion constituent (2–10 KeV)
Summary
Bursty bulk flows (BBFs) are the most common and significant phenomenon in the Earth's magnetotail (Baumjohann et al, 1990; Baumjohann, 2002; Angelopoulos et al, 1992, 1994; Zhang et al, 2009, 2015, 2015, 2016, 2016). Another mechanism is the dissipation of the BBF kinetic energy by emitting KAW (e.g., Angelopoulos et al, 2002; Chaston et al, 2012; Higashimori & Hoshino, 2015; Turkakin et al, 2014). The possible mechanism on the BBF deceleration is discussed
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