Interball-tail observations of vertical plasma motions in the magnetotail

Abstract

Abstract. The Interball spacecraft configuration favors, in contrast to previous experiments, investigation of vertical ion flows (GSM V z ). We use measurements of the CORALL instrument for the statistical study of V z and V y plasma flows in the mid-tail plasma sheet. In agreement with the previous observations, the mean V y was positive on the dusk side and negative on the dawn side. When IMF was southward, the mean V z consisted of the convection flow towards the equatorial plane ∼ 7 km/s and the northward flow ∼ 8 km/s. When IMF was northward, both components nearly vanished. The velocity variance was much larger than the mean values. The V z variance maximized on the dawn flank and was always 15-20% smaller than the V y one. The V y variance maximized in the pre-midnight sector closer to the neutral sheet. We conclude that velocity fluctuations are composed with the inherent high-beta plasma turbulence contributing to all components, and the BBF-related activity contributing mainly to V y in the pre-midnight plasma sheet.

Non‐self‐similar scaling of plasma sheet and solar wind probability distribution functions of magnetic field fluctuations

“…This nonlinear decrease is consistent with intermittent turbulence of the plasma sheet and with properties of non‐self‐similar scaling. These results are consistent with those previously reported for field fluctuations [ Weygand et al , 2005] and for flow fluctuations [ Borovsky et al , 1997, 2003; Angelopoulos et al , 1999; Petrukovich and Yermolaev , 2002]. Angelopoulos et al [1999] used two spacecraft (Geotail and Wind) to demonstrate intermittency in the plasma sheet flow.…”

“…Turbulence has been identified in the magnetospheric plasma sheet as well as in the solar wind. For plasma sheet studies different methods that have been used that include statistical examinations of PDFs of flow and magnetic field and the fluctuations of these quantities [ Borovsky et al , 1997; Angelopoulos et al , 1999; Petrukovich and Yermolaev , 2002; Weygand et al , 2005]. Most of these studies found non‐Gaussian PDFs of flow and magnetic field fluctuations from which they concluded that the plasma was turbulent.…”

“…They found the model was a good fit for the distributions of the BBF flows and the non‐BBF flows, but not for the distribution of the two combined. Using the CORALL instrument on the Interball Tail spacecraft, Petrukovich and Yermolaev [2002] examined the V y and V z flow components. The V x component values were considered to be less accurate then the other two components because the ion flux measurements were not measured within ±16° of the Sun‐pointing spin axis.…”

Tail lobe convection observed by Cluster/EDI

“…As shown in Figure 6, the deviation of the histogram is much larger than the averaged velocity for all conditions. This is the same for plasma sheet observations [ Angelopoulos et al , 1993; Petrukovich and Yermolaev , 2002]. However, while the high‐beta plasma in the plasma sheet may have a turbulent nature [ Angelopoulos et al , 1999], the lobe convection should be much more laminar, if compared with the polar cap convection.…”

MHD turbulence in the Earth's plasma sheet: Dynamics, dissipation, and driving

“…For some time it has been noted that the flows of the plasma sheet are irregular [e.g., Hones and Schindler , 1979; Hayakawa et al , 1982; Sergeev and Lennartsson , 1988; Angelopoulos et al , 1993; Nakamura et al , 1994; BEFT1997; Yermolaev et al , 2000; Ovchinnikov et al , 2000; Neagu et al , 2002; Petrukovich and Yermolaev , 2002]. Consistent with the turbulent flow velocities, large fluctuations in the electric field are observed by satellites in the plasma sheet [ Cattell and Mozer , 1982; Cattell et al , 1986; Pedersen et al , 1985; BEFT1997, Figure 8].…”