OCCURRENCE RATES AND HEATING EFFECTS OF TANGENTIAL AND ROTATIONAL DISCONTINUITIES AS OBTAINED FROM THREE-DIMENSIONAL SIMULATION OF MAGNETOHYDRODYNAMIC TURBULENCE
MHD discontinuities are ubiquitous in the solar wind and are often found at the origin of turbulence intermittency. They may also play a key role in the turbulence dissipation and heating of the solar wind. The tangential discontinuities (TDs) and rotational discontinuities (RDs) are the two most important types of discontinuities. Recently, the connection between turbulence intermittency and proton thermodynamics has been observationally investigated. Here, we present numerical results from a three-dimensional MHD simulation with pressure anisotropy and we define new methods for identifying and distinguishing TDs and RDs. Three statistical results obtained for the relative occurrence rates and heating effects are highlighted: (1) RDs tend to take up the majority of the discontinuities along with time; (2) the thermal states embedding TDs tend to be associated with extreme plasma parameters or instabilities while RDs do not; (3) TDs have a higher average T as well as perpendicular temperature T_perp. The simulation shows that TDs and RDs evolve and contribute to solar wind heating differently. These results will improve our understanding of the mechanisms that generate discontinuities and cause plasma heating.
Fig. 1 Absolute (left) and relative (right) occurrence rates of four different types of discontintuities (TD, RD, ED, and ND)
Fig. 2 Difference of T, T_para, and T_perp between TDs and RDs.
The article is available at http://iopscience.iop.org/2041-8205/804/2/L43/. To cite: Lei Zhang et al. 2015 ApJ 804 L43 doi:10.1088/2041-8205/804/2/L43
This article is finished in collaboration with Uni. Kiel (Germany) and National Space Centre of CAS. The research was supported by NSFC grants under contracts 41231069, 41174148, 41222032, 41274132, 41474147, 41031066, and 41304133.
L. Zhang would like to thank the author(s) of SMWF/BATSRUS, Vapor, R and Matplotlib.