Turbulence-generated proton-scale structures in the terrestrial magnetosheath

Recent results of numerical magnetohydrodynamic simulations suggest that in collisionless space plasmas turbulence can spontaneously generate thin current sheets. These coherent structures can partially explain intermittency and the non-homogenous distribution of localized plasma heating in turbulence. In this Letter Cluster multi-point observations are used to investigate the distribution of magnetic field discontinuities and the associated small-scale current sheets in the terrestrial magnetosheath downstream of a quasi-parallel bow shock. It is shown experimentally, for the first time, that the strongest turbulence generated current sheets occupy the long tails of probability distribution functions (PDFs) associated with extremal values of magnetic field partial derivatives. During the analyzed one hour long time interval, about a hundred strong discontinuities, possibly proton-scale current sheets were observed.Comment: 10 pages, 5 figures in The Astrophysical Journal Letters, Volume 819, Number 1, 201

Solar wind turbulence at 0.72 AU and solar minimum

We investigate Venus Express (VEX) observations of magnetic field fluctuations performed systematically in the solar wind at 0.72 Astronomical Units (AU), between 2007 and 2009, during the deep minimum of the solar cycle 24. The Power Spectral Densities (PSD) of the magnetic field components have been computed for the time intervals that satisfy data integrity criteria and have been grouped according to the type of wind, fast and slow defined for speeds larger and respectively smaller than 450 km/s. The PSDs show higher levels of power for the fast than for the slow wind. The spectral slopes estimated for all PSDs in the frequency range 0.005-0.1 Hz exhibit a normal distribution. The average value of the trace of the spectral matrix is -1.60 for fast solar wind and -1.65 for slow wind. Compared to the corresponding average slopes at 1 AU, the PSDs are shallower at 0.72 AU for slow wind conditions suggesting a steepening of the solar wind spectra between Venus and Earth. No significant time variation trend is observed for the spectral behavior of both slow and fast wind

Complexity Phenomena and ROMA of the Magnetospheric Cusp, Hydrodynamic Turbulence, and the Cosmic Web

Dynamic Complexity is a phenomenon exhibited by a nonlinearly interacting system within which multitudes of different sizes of large scale coherent structures emerge, resulting in a globally nonlinear stochastic behavior vastly different from that could be surmised from the underlying equations of interaction. The hallmark of such nonlinear, complex phenomena is the appearance of intermittent fluctuating events with the mixing and distributions of correlated structures at all scales. We briefly review here a relatively recent method, ROMA (rank-ordered multifractal analysis), explicitly constructed to analyze the intricate details of the distribution and scaling of such types of intermittent structures. This method is then applied to the analyses of selected examples related to the dynamical plasmas of the cusp region of the magnetosphere, velocity fluctuations of classical hydrodynamic turbulence, and the distribution of the structures of the cosmic gas obtained through large scale, moving mesh simulations. Differences and similarities of the analyzed results among these complex systems will be contrasted and highlighted. The first two examples have direct relevance to the geospace environment and are summaries of previously reported findings. The third example on the cosmic gas, though involving phenomena much larger in spatiotemporal scales, with its highly compressible turbulent behavior and the unique simulation technique employed in generating the data, provides direct motivations of applying such analysis to studies of similar multifractal processes in various extreme environments. These new results are both exciting and intriguing.Comment: 36 page

Magnetopause properties at the dusk magnetospheric flank from global magnetohydrodynamic simulations, the kinetic Vlasov equilibrium, and in situ observations − Potential implications for SMILE

We derived the properties of the terrestrial magnetopause (MP) from two modeling approaches, one global–fluid, the other local–kinetic, and compared the results with data collected in situ by the Magnetospheric Multiscale 2 (MMS2) spacecraft. We used global magnetohydrodynamic (MHD) simulations of the Earth’s magnetosphere (publicly available from the NASA-CCMC [National Aeronautics and Space Administration–Community Coordinated Modeling Center]) and local Vlasov equilibrium models (based on kinetic models for tangential discontinuities) to extract spatial profiles of the plasma and field variables at the Earth’s MP. The global MHD simulations used initial solar wind conditions extracted from the OMNI database at the time epoch when the MMS2 observes the MP. The kinetic Vlasov model used asymptotic boundary conditions derived from the same in situ MMS measurements upstream or downstream of the MP. The global MHD simulations provide a three-dimensional image of the magnetosphere at the time when the MMS2 crosses the MP. The Vlasov model provides a one-dimensional local view of the MP derived from first principles of kinetic theory. The MMS2 experimental data also serve as a reference for comparing and validating the numerical simulations and modeling. We found that the MP transition layer formed in global MHD simulations was generally localized closer to the Earth (roughly by one Earth radius) from the position of the real MP observed by the MMS. We also found that the global MHD simulations overestimated the thickness of the MP transition by one order of magnitude for three analyzed variables: magnetic field, density, and tangential speed. The MP thickness derived from the local Vlasov equilibrium was consistent with observations for all three of these variables. The overestimation of density in the Vlasov equilibrium was reduced compared with the global MHD solutions. We discuss our results in the context of future SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) campaigns for observing the Earth’s MP

Space plasma physics science opportunities for the lunar orbital platform - Gateway

The Lunar Orbital Platform - Gateway (LOP - Gateway, or simply Gateway) is a crewed platform that will be assembled and operated in the vicinity of the Moon by NASA and international partner organizations, including ESA, starting from the mid-2020s. It will offer new opportunities for fundamental and applied scientific research. The Moon is a unique location to study the deep space plasma environment. Moreover, the lunar surface and the surface-bounded exosphere are interacting with this environment, constituting a complex multi-scale interacting system. This paper examines the opportunities provided by externally mounted payloads on the Gateway in the field of space plasma physics, heliophysics and space weather, and also examines the impact of the space environment on an inhabited platform in the vicinity of the Moon. It then presents the conceptual design of a model payload, required to perform these space plasma measurements and observations. It results that the Gateway is very well-suited for space plasma physics research. It allows a series of scientific objectives with a multi-disciplinary dimension to be addressed

Kinetic investigation of the impulsive penetration of 2D plasma elements into the Earth's magnetosphere

In this thesis I investigate the dynamics of charged particles and plasma into non-uniform distributions of the electric and magnetic fields(PHYS 3) -- UCL, 200