PIC Simulation on Plasma Flow Response to a Mesoscale Magnetic Dipole in Space

Abstract

We have been studying plasma flow response to a mesoscale magnetic dipole in space by means of full kinetic simulations using Particle-In-Cell method. The size of magnetic dipole structure is characterized by distance L at which the pressure equilibrium is satisfied between the dipole magnetic field and the plasma flow under the MHD approximation. We focus on a mesoscale magnetic dipole in which L is smaller than the ion Larmor radius or the ion inertial length but larger than the electron Lamor radius. In this situation, the plasma kinetics such as finite Larmor radius effect will play an important role to determine the plasma response to the magnetic dipole. In the simulations, we found that a mesoscale magnetosphere is created even though the magnetization of ions is weak. In the dayside region, charge separation occurs because of the difference of dynamics between magnetized electrons and unmagnetized ions and intense electrostatic field is induced. The incoming ion flow to the dipole fields is eventually influenced by this electric field and the ions’ trajectories are largely distorted. The width of the boundary current layer as well as the spatial gradient of the local magnetic field compression in the dayside region can be characterized by the electron Larmor radius and is independent of ion’s spatial scale. Meanwhile the KAGUYA spacecraft also observed ion reflection and electron heating and acceleration over crustal magnetic anomalies on the lunar surface. By performing threedimensional PIC simulation, we started to examine the solar wind interactions with the magnetic anomaly called Reiner Gamma on the lunar surface. We will discuss some of the simulation results on the plasma behavior over the magnetic anomaly.