MMS observation of anisotropic particle distributions in an Alfvén Vortex----中国科学院紫金山天文台

Seminar Title	MMS observation of anisotropic particle distributions in an Alfvén Vortex

Speaker:	Prof. WANG Tieyan

Affiliation:	(Rutherford Appleton Laboratory)

When	Wednesday afternoon, Aug. 28, 15:00 p.m.

Where:	Room 208 No.5 building , Xianlin campus (PMO, CAS)
	Welcome to Attend

	( PMO Academic Committee & Academic Circulating committee)

Abstract: The Alfvén vortex is one of the non-linear solutions of the ideal incompressible MHD equations. It is characterized by aligned magnetic field and velocity fluctuations mostly perpendicular to the unperturbed magnetic field. Alfvén vortices have been widely reported in the magnetosheath and solar wind. Most of them are found to be monopole type, with scales ranging from MHD to ion scales. Due to the limited temporal resolution of the plasma instrument on previous missions, most of the Alfvén vortices have been identified solely on basis of magnetic field measurement. Direct measurements of the flow properties are lacking. Moreover, the plasma properties, especially the velocity distribution functions (VDFs) accompanied with Alfvén vortices still remains blank. This leads us to wonder, what are the plasma behaviors within Alfvén vortices? Based on high-resolution measurements from the MMS mission, here we present an example of Alfvén vortex, where both ions and electrons exhibit distinctive characteristics within this structure. Furthermore, Deformations of the VDFs, featuring elongations along or across the magnetic field, are found to be modulated by velocity and magnetic gradients. Therefore, our results provide evidence of local kinetic processes within this structure, which may help to understand the intermittent heating and energy transfer processes in the weakly collisional space plasmas.