Isotropy restoration toward high-beta space plasmas

Abstract

Wavevector anisotropy of ion-scale plasma turbulence is studied at various values of beta. Two complementary methods are used. One is multi-point measurements of magnetic field in the near-Earth solar wind as provided by the Cluster spacecraft mission, and the other is hybrid numerical simulation of two-dimensional plasma turbulence. The both methods provide evidence of wavevector anisotropy as a function of beta such that isotropy is gradually restored toward higher values of beta. Furthermore, the numerical simulation study demonstrates the existence of scaling law between plasma beta and wavevector anisotropy. This fact can be used to construct a diagnostic tool to determine or to constrain plasma beta using multi-point magnetic field measurements in space.