Earthward flow bursts in the inner magnetotail and their relation to auroral brightenings, AKR intensifications, geosynchronous particle injections and magnetic activity

Abstract

Abstract. High-velocity magnetotail flow bursts measured by the Geotail Low Energy Plasma experiment in the premidnight equatorial region between 10 and 15 RE have been compared with other magnetospheric phenomena. These bursts, typically characterized by earthward velocities approaching 1000 km/s and lasting for times of the order of 1 min, are associated with magnetotail dipolarizations and large magnetic field fluctuations. Using supporting measurements of the International Solar Terrestrial Physics program it is found that the flow bursts are closely associated with auroral brightenings, AKR onsets, geosynchronous particle injections, and ground magnetic activity. Flow bursts for which Polar UVI images are available showed auroral brightenings that developed near the footpoint Geotail field line. AKR intensifications usually accompanied the flow bursts in close time coincidence, whereas dispersionless geosynchronous particle injections tended to be delayed by 1-3 min. Since flow bursts often exhibit the earliest onsets of these various phenomena, it seems likely that this chain of events is initiated in the tail beyond 15 RE, presumably by magnetic reconnection. It is concluded that flow bursts are a fundamental magnetotail process of limited spacial extent that are important in energy and magnetic flux transport in the magnetosphere. Magnetotail flow bursts are intimately connected to auroral acceleration processes and AKR generation at several thousand kilometer altitude and a full explanation of substorms will have to explain this relationship.

A coupled‐map model for the magnetotail current sheet

“…This turbulent behavior is supported by satellite observations of bursty flows in the near-earth magnetotail [Angelopoulos et al, 1992;Lui, 1998;Fairfield et al, 1999]. These turbulent bursts are proposed to be connected to the local reconnection sites in the plasma sheet.…”

Energy conversion regions as observed by Cluster in the plasma sheet

“…BBFs are believed to play a major role for magnetic flux, mass, and energy transport in the plasma sheet [e.g., Angelopoulos et al, 1992Angelopoulos et al, , 1994Angelopoulos et al, , 1999Sergeev et al 1996b;Schödel et al, 2001], and it has been showed that BBFs have the largest capability of transporting energy during the substorm expansion phase, as compared to the growth and recovery phases [YuDuan et al, 2010]. In the literature there are many reports of the relation between BBFs and auroral phenomena at the ionospheric end of the M-I coupling system, e.g., auroral expansions, localized brightenings, and auroral streamers [e.g., Fairfield et al, 1999;Lyons et al, 1999;Ieda et al, 2001;Sergeev et al, 2001;Nakamura et al, 2001aNakamura et al, , 2001bNakamura et al, , 2005bMiyashita et al, 2003;Forsyth et al, 2008].…”

“…Therefore, it is practical to include also the field aligned beams into the definition of BBFs [Snekvik et al, 2007]. Observational investigations have shown that BBFs often are associated with ion heating and local magnetic field dipolarization (magnetic pileup) at the front or stopping region, corresponding to a locally enhanced northward B z [e.g., Fairfield et al, 1999;Nakamura et al, 2005a;Sergeev et al, 1996b]. The BBFs are likely to show a reduction in the plasma pressure initially, but evolving toward values comparable to, or sometimes even greater, than the surrounding medium [Chen and Wolf, 1999].…”

High time resolution observations of magnetospheric disturbances during auroral activity

“…Many of the same features in the plasma sheet have been noted by Angelopoulos et al [1997] and Fairfield et al [1999] in conjunction with substorm onsets and intensifications identified using global auroral images. The typical interpretation for the large ion velocity moments is that they are caused by an enhanced, quasistatic electric field resulting in a large E × B drift.…”