Local Kinetic Effects in Two-Dimensional Plasma Turbulence

Abstract

Using direct numerical simulations of a hybrid Vlasov-Maxwell model, kinetic processes are investigated in a two-dimensional turbulent plasma. In the turbulent regime, kinetic effects manifest through a deformation of the ion distribution function. These patterns of non-Maxwellian features are concentrated in space nearby regions of strong magnetic activity: the distribution function is modulated by the magnetic topology, and can elongate along or across the local magnetic field. These results open a new path on the study of kinetic processes such as heating, particle acceleration, and temperature anisotropy, commonly observed in astrophysical and laboratory plasmas.

Intermittency, nonlinear dynamics and dissipation in the solar wind and astrophysical plasmas

“…Recently, a PVIbased method was implemented to search for solar wind reconnection sites. The method was tested in the context of MHD simulation [95], where current sheets and reconnection rates can be unambiguously identified by full analysis of the MHD fields. It was found that, for strong events with PVI >6 or 7, it was extremely likely that these would also be located at reconnecting current sheets.…”

“…Eulerian Vlasov) [95,139]. This method is computationally very expensive but has the distinct advantage of resolving with good fidelity and resolution various properties of the plasma velocity distribution functions.…”

“…Therefore, at present the strength of these codes is in resolving properties of the proton distribution functions, rather than studying scaling or intermittency measures. Hybrid (kinetic protons, fluid electrons) 2.5-dimensional Eulerian Vlasov computations have been able to very well describe coherent current structures near reconnection sites and their statistical association with nearby or co-located regions of kinetic activity such as temperature anisotropies and heat fluxes [95,140,141] (see figure 12 for an illustration). Moreover, results from 2.5-dimensional Eulerian Vlasov codes demonstrate that turbulence can generate distinctive kinetic effects that appear in the β , T ⊥ /T plane (parallel plasma beta versus proton temperature anisotropy) [142], and these are similar to observed solar wind features [143][144][145][146].…”

“…However, it is also clear that new effects enter, such as the distribution of the turbulent heating into various species [147,148] and a new type of intermittency [95,130] which is the concentration of kinetic features such as anisotropies in coherent structures.…”

Multipoint observations of plasma phenomena made in space by Cluster

“…In this interpretation, current sheets are characteristic coherent structures expected in active intermittent MHD turbulence and are therefore integral to the dynamical couplings across scales. It is quite possible that discontinuities are related to both flux tube boundaries and intermittent structures that appear spontaneously in MHD turbulence (Matthaeus and Montgomery 1980;Matthaeus et al 1986b;Carbone et al 1990; Veltri and Mangeney 1999; Vasquez (Osman et al 2011;Servidio et al 2012;Wan et al 2012;Perrone et al 2013;Wu et al 2013). There is evidence suggesting that increased helium, proton and electron temperature anisotropies are linked to near-discontinuous structures.…”