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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The edge plasma turbulence in the T-10 tokamak, the HYBTOK-II tokamak, the linear machine NAGDIS-II and the Large Helical Device have been studied. The fluctuations in the plasma density have been analysed in terms of the multifractal formalism revisited with wavelets.In most of the cases considered, the edge density fluctuations demonstrate multifractal statistics, i.e. the scaling behaviour of the absolute moments is described by a convex function with non-trivial self-similarity properties. The multifractality factor defined in the multiplicative cascade model is a relevant parameter for characterizing the edge plasma turbulence. The multiplicative cascade process has a ‘coarse’ time scale T ∼ 50–200 ms iterating towards finer scales. This time scale is referred to as an integral correlation scale. The self-similarity parameters have been observed to depend on the edge plasma condition. The correlation and transport properties have been analysed regarding the multifractality parameter. The diffusion transport coefficient in an edge plasma is not a trivial function of multifractality parameters.

Plasma periphery investigation performed in the T-10 tokamak has shown an essential increase of the perpendicular anomalous particle flux in the scrapeoff layer (SOL) with an average plasma density rise. The strengthening of the radial transport is found to occur at an average electron density above a threshold level, which depends on a plasma current I p . The value of the threshold level is about 0.3 times the Greenwald density. Langmuir probe measurements of SOL plasma parameters indicate that intermittent events can play a significant role in the cross-field transport. Intermittent behaviour of the plasma parameters is associated with formation and propagation of the plasma regions (or structures) with high density. The structures move in radial and poloidal directions. Radial movement is predominantly directed to the vacuum vessel wall in the SOL. The radial velocity of the high density plasma structures reduces from 1000 m s −1 near the last closed flux surface to 200 m s −1 at the wall of the vacuum chamber. The radial size of the structures also decreases with minor radius from 3 to 0.5 cm. The poloidal velocity is equal to 1000-1300 m s −1 and is directed towards an ion diamagnetic velocity; the poloidal size of the plasma structures is 2-3 cm. The observed plasma structures can be responsible for more than 50% of the total radial turbulent particle flux. T-10 results support the hypothesis that intermittent convection rather than diffusion can define the cross-field transport.

The paper presents the latest results of the studies of small-scale fluctuations in a turbulent flow of solar wind (SW) using measurements with extremely high temporal resolution (up to 0.03 s) of the bright monitor of SW (BMSW) plasma spectrometer operating on astrophysical SPECTR-R spacecraft at distances up to 350 000 km from the Earth. The spectra of SW ion flux fluctuations in the range of scales between 0.03 and 100 s are systematically analysed. The difference of slopes in low- and high-frequency parts of spectra and the frequency of the break point between these two characteristic slopes was analysed for different conditions in the SW. The statistical properties of the SW ion flux fluctuations were thoroughly analysed on scales less than 10 s. A high level of intermittency is demonstrated. The extended self-similarity of SW ion flux turbulent flow is constantly observed. The approximation of non-Gaussian probability distribution function of ion flux fluctuations by the Tsallis statistics shows the non-extensive character of SW fluctuations. Statistical characteristics of ion flux fluctuations are compared with the predictions of a log-Poisson model. The log-Poisson parametrization of the structure function scaling has shown that well-defined filament-like plasma structures are, as a rule, observed in the turbulent SW flows.

Experimental investigation of the Scrape-Off Layer (SOL) turbulence and the perpendicular anomalous particle transport in the high density regime in the T-10 tokamak is presented. Comparison of the plasma parameters measured at the low-field side (LFS) and the high-field side (HFS) of the tokamak shows that the inboard turbulence essentially differs from the outboard one. Turbulence has an intermittent character but the fluctuation level of the inboard ion saturation current is about two times lower than at the LFS. The radial turbulent particle flux and the effective perpendicular diffusion coefficient measured at the LFS are about 3-5 times higher than those observed at the HFS. Enhanced perpendicular particle flux at the LFS is defined by the high density plasma structures formed in the vicinity of the last closed flux surface. The poloidal electric field inside the high density structures has different directions at the inboard and outboard sides of the plasma column. The radial electric drift induced by the poloidal electric field is directed towards the vacuum vessel at both the LFS and the HFS. These experiments support the hypothesis that SOL parallel flow might be caused by an additional mechanism such as 'ballooning' transport, which generates a larger flux of particles from the core into the SOL at the outer mid-plane.

Fractal structure of the edge turbulence and enhanced turbulent transport have been studied in the tokamak HYBTOK-II with a variation of the rotating helical magnetic field (RHF) frequency in the range 5-30 kHz. Edge fluctuations have non-Gaussian statistics caused by intermittent bursts with a time scale of 40-100 µs. The variation in the RHF frequency has a selective effect on the fractal structure of edge turbulence and the turbulent flux, demonstrating a selective control of the transport process. A delayed synchronization control of resonant drift wave modes by the RHF is considered as a candidate mechanism to explain the dependence of the effect on the RHF frequency.