High-speed flowing plasmas in the Earth’s plasma sheet

Abstract

A research topic of great interest to the space physics community is the observation of plasmas flowing at hundreds of kilometers per second in the Earth's plasma sheet. Although considerable effort has been made to understand the source of fast-flowing plasmas, many questions remain unanswered about the mechanisms that produce high-speed flows and the effects they have on magnetospheric disturbances, especially their contributions to magnetospheric convection and substorms. In this paper, we discuss briefly the history of high-speed flows and review the proposed mechanisms, signatures of high-speed flows in auroras and their interaction with the background plasma. We then summarize the relationships between high-speed flows and magnetic structures, discuss questions associated with substorms, and finally pose several important scientific questions that need to be addressed. plasma sheet, high speed flow, magnetic structure, substorm, dipolarization Citation:Fu S Y, Shi Q Q, Wang C, et al. High-speed flowing plasmas in the Earth's plasma sheet.

Electromagnetic disturbances observed near the dip region ahead of dipolarization front

“…Bursty bulk flows (BBFs) are fast flowing plasma with a speed of several hundred kilometers per second in the magnetotail plasma sheet. Extensive studies have revealed that BBFs play an important role in substorm activities [e.g., Angelopoulos et al, 1992Angelopoulos et al, , 1994Fu et al, 2011;Liu et al, 2014]. Dipolarization fronts (DFs) are frequently observed in the BBFs, which are often characterized as sharp enhancement of magnetic field (B z ) and decrease of plasma density [e.g., Sergeev et al, 1996;Nakamura et al, 2002;Runov et al, 2009;Liu et al, 2013;Sun et al, 2014a].…”

Field‐aligned currents associated with dipolarization fronts

“…Sitnov et al [] suggested that DFs can result from transient magnetic reconnection in the near‐earth magnetotail moving earthward embedded in bursty bulk flows [ Angelopoulos et al , ; Fu et al , ]. A spacecraft observing a DF thus sees an enhancement of B z , which subsequently decreases over several minutes [ Ohtani et al , ].…”

Downward current electron beams observed at the dipolarization front

“…The relation of field-aligned current and the braking or deflection of the high speed flows has been studied [17][18][19][20]. Vortex-like plasma flow induced field-aligned current has been observed at the high latitude and 1 keV outflowing oxygen ions from the ionosphere are reported together with the current [21].…”