报告内容摘要

Solar wind plasma may be described by magnetohydrodynamics at large scales, with existence of an energy cascade where energy is transferred from large to smaller scales. This also requires kinetic description at kinetic scales to include dissipative processes that terminate the cascade. Solar wind magnetic field observations also show the formation of internal boundaries and coherent structures with characteristic correlations.  Recently evidence is accumulating that these structures are a manifestation of turbulence intermittency. In this talk I will review some of our recent works on the study of intermittency and dissipation in solar wind turbulence with MHD and kinetic plasma simulations, as well as solar wind observations. With high resolution kinetic simulations of collisionless plasma, we show the development of turbulence characterized by sheet-like current density structures spanning a range of scales down to electron scales. We present evidence that these structures are sites for heating and dissipation, and that stronger current structures signify higher dissipation rates. Evidently, kinetic scale plasma, like MHD, becomes intermittent due to current sheet formation, leading to the expectation that heating and dissipation in astrophysical and space plasmas may be highly non-uniform and patchy.  We also compare high-resolution spacecraft observations with MHD and kinetic plasma simulations. Kurtosis of increments indicates that kinetic scale coherent structures are present. Conditioned proton temperature distributions suggest heating associated with coherent structures. These results reinforce the association of intermittent turbulence, coherent structures, and plasma dissipation in solar wind.

报告人

Minping Wan 教授

Department of Physics and Astronomy, University of Delaware

欢迎广大老师和学生参加！