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593The region downstream of a supercritical collisionless shock, the magnetosheath (MSH), is known to be in a highly disturbed turbulent state [1][2][3]. The undisturbed solar wind (SW) streams with supermagnetosonic velocity V > c ms at a magnetosonic Mach number up to M ms ~ 15. At the Earth's bow shock (BS), the SW decelerates to Mach numbers M ms < 1, thermalizes, and, when entering the MSH, is compressed by roughly a factor of 4. The flow downstream of the BS is highly disturbed and turbulent. However, the MSH is not spacious enough for the turbulence to reach a quasi-sta- ¶ The text was submitted by the authors in English.tionarity. It remains not fully developed, intermittent, and structured in time and space. In this framework, high-energy density jets have been observed in the past in the magnetosheath [1,5]. As a development of such earlier studies, we have found more than 140 events of an anomalously high kinetic energy density in the MSH during 20 orbits of Interball-1 , Cluster , Polar , and Geotail . Here, we concentrate on two MSH crossings-by Interball-1 and Cluster [11], respectively-characterized by the bursts of an extraordinarily high ion flux and kinetic energy density. High energy density jets in the magnetosheath near the Earth magnetopause were observed by Interball-1 [1]. In this paper, we continue the investigation of this important physical phenomenon. New data provided by Cluster show that the magnetosheath kinetic energy density during more than one hour exhibits an average level and a series of peaks far exceeding the kinetic energy density in the undisturbed solar wind. This is a surprising finding because the kinetic energy of the upstream solar wind in equilibrium should be significantly diminished downstream in the magnetosheath due to plasma braking and thermalization at the bow shock. We suggest resolving the energy conservation problem by the fact that the nonequilibrium jets appear to be locally superimposed on the background equilibrium magnetosheath, and, thus, the energy balance should be settled globally on the spatial scales of the entire dayside magnetosheath. We show that both the Cluster and Interball jets are accompanied by plasma superdiffusion and suggest that they are important for the energy dissipation and plasma transport. The character of the jet-related turbulence strongly differs from that of known standard cascade models. We infer that these jets may represent the phenomenon of the general physical occurrence observed in other natural systems, such as heliosphere, astrophysical, and fusion plasmas [2][3][4][5][6][7][8][9][10]. High Energy Jets in the Earth

Abstract. We present multi spacecraft measurements in the magnetosheath (MSH) and in the solar wind (SW) by Interball, Cluster and Polar, demonstrating that coherent structures with magnetosonic Mach number up to 3 -Supermagnetosonic Plasma Streams (SPS) -generate transient and anomalous boundary dynamics, which may cause substantial displacements of the magnetospheric boundaries and the riddling of peripheral boundary layers. In this regard, for the first time, we describe a direct plasma penetration into the flank boundary layers, which is a candidate for being the dominant transport mechanism for disturbed MSH periods.Typically SPS's have a ram pressure exceeding by several times that of the SW and lead to long-range correlations between processes at the bow shock (BS) and at the magnetopause (MP) on one side and between MSH and MP boundary layers on the other side. We demonstrate that SPS's can be observed both near the BS and near the MP and argue that they are often triggered by hot flow anomalies (HFA), which represent local obstacles to the SW flow and can induce the SPS generation as a means for achieving a local flow balance. Finally, we also discuss other causes of SPS's, both SW-induced and intrinsic to the MSH.SPS's appear to be universal means for establishing a new equilibrium between flowing plasmas and may also prove to be important for astrophysical and fusion applications.

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Abstract. We advance the achievements of Interball-1 and other contemporary missions in exploration of the magnetosheath-cusp interface. Extensive discussion of published results is accompanied by presentation of new data from a case study and a comparison of those data within the broader context of three-year magnetopause (MP) crossings by Interball-1. Multi-spacecraft boundary layer studies reveal that in ∼80% of the cases the interaction of the magnetosheath (MSH) flow with the high latitude MP produces a layer containing strong nonlinear turbulence, called the turbulent boundary layer (TBL). The TBL contains wave trains with flows at approximately the Alfvén speed along field lines and "diamagnetic bubbles" with small magnetic fields inside. A comparison of the multi-point measurements obtained on 29 May 1996 with a global MHD model indicates that three types of populating processes should be operative:-large-scale (∼few R E ) anti-parallel merging at sites remote from the cusp; -medium-scale (few thousand km) local TBL-merging of fields that are anti-parallel on average;Correspondence to: S. Savin (ssavin@iki.rssi.ru) -small-scale (few hundred km) bursty reconnection of fluctuating magnetic fields, representing a continuous mechanism for MSH plasma inflow into the magnetosphere, which could dominate in quasi-steady cases.The lowest frequency (∼1-2 mHz) TBL fluctuations are traced throughout the magnetosheath from the post-bow shock region up to the inner magnetopause border. The resonance of these fluctuations with dayside flux tubes might provide an effective correlative link for the entire dayside region of the solar wind interaction with the magnetopause and cusp ionosphere. The TBL disturbances are characterized by kinked, double-sloped wave power spectra and, most probably, three-wave cascading. Both elliptical polarization and nearly Alfvénic phase velocities with characteristic dispersion indicate the kinetic Alfvénic nature of the TBL waves. The three-wave phase coupling could effectively support the self-organization of the TBL plasma by means of coherent resonant-like structures. The estimated characteristic scale of the "resonator" is of the order of the TBL dimension over the cusps. Inverse cascades of kinetic Alfvén waves are proposed for forming the larger scale "organizing" structures, which in turn synchronize all nonlinear cascades within the TBL in a self-consistent manner. This infers a qualitative differ-184 S. Savin et al.: Magnetosheath-cusp interface ence from the traditional approach, wherein the MSH/cusp interaction is regarded as a linear superposition of magnetospheric responses on the solar wind or MSH disturbances.

Abstract. We study properties of nonlinear magnetic fluctuations in the turbulent boundary layer (TBL) over polar cusps during a typical TBL crossing on 19 June 1998. Interball-1 data in the summer TBL are compared with that of Geotail in solar wind (SW) and Polar in the northern TBL. In the TBL two characteristic slopes are seen: ∼ − 1 at (0.004-0.08) Hz and ∼ − 2.2 at (0.08-2) Hz. We present evidences that random current sheets with features of coherent solitons can result in: (i) slopes of ∼ − 1 in the magnetic power spectra; (ii) demagnetization of the SW plasma in "diamagnetic bubbles"; (iii) nonlinear, presumably, 3-wave phase coupling with cascade features; (iiii) departure from the Gaussian statistics. We discuss the above TBL properties in terms of intermittency and self-organization of nonlinear systems, and compare them with kinetic simulations of reconnected current sheet at the nonlinear state. Virtual satellite data in the model current sheet reproduce valuable cascade-like spectral and bi-spectral properties of the TBL turbulence.

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.