Magnetosheath Interaction with the High Latitude Magnetopause

Abstract

We present both statistical and case studies of magnetosheath interaction with the high-latitude magnetopause on the basis of Interball-1 and other ISTP spacecraft data. We discuss those data along with recently published results on the topology of cusp-magnetosheath transition and the roles of nonlinear disturbances in mass and energy transfer across the high-latitude magnetopause. For sunward dipole tilts, a cusp throat is magnetically open for direct interaction with the incident flow that results in the creation of a turbulent boundary layer (TBL) over an indented magnetopause and downstream of the cusp. For antisunward tilts, the cusp throat is closed by a smooth magnetopause; demagnetized 'plasma balls' (with scale~few R E , an occurrence rate of~25% and trapped energetic particles) present a major magnetosheath plasma channel just inside the cusp. The flow interacts with the 'plasma balls' via reflected waves, which trigger a chaotization of up to 40% of the upstream kinetic energy. These waves propagate upstream of the TBL and initiate amplification of the existing magnetosheath waves and their cascade-like decays during downstream passage throughout the TBL. The most striking feature of the nonlinear interaction is the appearance of magnetosonic jets, accelerated up to an Alfvenic Mach number of 3. The characteristic impulsive local momentum loss is followed by decelerated Alfvenic flows and modulated by the TBL waves; momentum balance is conserved only on time scales of the Alfvenic flows (1/f A~1 2 min). Wave trains at f A~1 .3 mHz are capable of synchronizing interactions throughout the outer and inner boundary layers. The sonic/Alfvenic flows, bounded by current sheets, control the TBL Surveys in Geophysics (2005) 26: 95-133 Ó Springer 2005 spectral shape and result in non-Gaussian statistical characteristics of the disturbances, indicating the fluctuation intermittency. We suggest that the multi-scale TBL processes play at least a comparable role to that of macro-reconnection (remote from or in the cusp) in solar wind energy transformation and population of the magnetosphere by the magnetosheath plasma. Secondary micro-reconnection constitutes a necessary chain at the small-scale (~ion gyroradius) edge of the TBL cascades. The thick TBL transforms the flow energy, including deceleration and heating of the flow in the open throat, 'plasma ball' and the region downstream of the cusp.

High energy jets in the Earth’s magnetosheath: Implications for plasma dynamics and anomalous transport

“…This was also the case on June 19, 1998 [1,19]. Thus, the jets can provide a considerable input into a quasi-static flow balance in the MSH.…”

“…To that extent, we first recall a mechanism based on an inertial-drift plasma acceleration by nonuniform electric field structures [1,4,19] almost standing in the MP frame, which can account for the enhanced-jet velocities. Such structures constitute wave interference patterns in the MSH [19] with an electric field forcing the incident flow into an equilibrium state that adjusts for the presence of the moving boundaries [4] and transfers the momentum downstream the MSH by means of the jet formation. Now, we would like to discuss in further detail the implications of the HKPJs for the turbulence and transport characteristics.…”

“…Thus, qualitatively, we conclude that the MSH turbulence including HKPJs exhibits signs of the plasma superdiffusion and anomalous plasma transport. It should affect the effective deceleration of the MSH flow closer to the MP (i.e., dissipate the kinetic energy in boundary layers) via carrying the downflow of the momentum "excess" by the jets [1,19], supporting the SW plasma penetration across the high-latitude MP. Note that about 20% of the strongest jets on March 27, 2002 (see Fig.…”

Super fast plasma streams as drivers of transient and anomalous magnetospheric dynamics

“…At the same time, both modeling and experimental studies highlight 10 % as a characteristic value for the MSH flow penetration into high-latitude boundary layer through diffusive-like or reconnection-like processes (see e.g. Savin et al, 2005a, b, and references therein).…”

Spatial structures of magnetic depression in the Earth's high‐altitude cusp: Cluster multipoint observations

“…As a very complex region of the magnetosphere, the cusp is found to have several clear and unclear boundaries [e.g., Lavraud et al , 2005; Cargill et al , 2005; Zhang et al , 2007] and to be filled with spatial and temporal variations [e.g., Wing et al , 2001; Trattner et al , 2002; Zong et al , 2004; Cargill et al , 2005]. The cusp boundary layers are also found to be turbulent [ Haerendel et al , 1978; Savin et al , 2005]. Multipoint observations have helped us to distinguish the temporal events from spatial ones.…”