Particle Energization in 3-D Kelvin-Helmholtz (KH) Instability Simulation

The Kelvin-Helmholtz (KH) instability plays an important role for the transport processes at the Earth's magnetopause. It is important to note that 3-D KH instability in the nonlinear stage is fundamentally different from a 2-D treatment. For northward interplanetary magnetic field (IMF) conditions, KH vorticity dramatically twists the magnetic field and triggers a pair of high-latitude magnetic reconnection sites. This double-reconnection process interchanges a part of the flux tube, exchanging the magnetosheath and magetospheric plasma. For southward IMF conditions, the nonlinear interaction between the KH instability and reconnection forms a complex flux rope structure at low latitudes. What are the dynamics of charged particles in such complex 3-D configuration? This compelling question, however, has not been well explored. We approach this question by using test-particles in fluid simulations to investigate the possible heating and acceleration mechanisms associated with 3-D mesoscale KH instability. It is shown that ions can be heated by the shock-like structure associated with KH instability driven by a large sheared flow (i.e., close to the Alfven speed). The comparison between simulation results and recent in-situ observational data will also be discussed in this presentation.