Bulk Ion Heating and Acceleration in Large-Scale Reconnecting Current Sheets

We study the bulk heating and acceleration of ions in reconnecting current sheets much larger (100s of ion skin depths) than the ion kinetic scales. The initial ion acceleration includes a pickup mechanism as ions cross into the reconnection outflow jet [1], which generates a pressure anisotropy that reduces the effectiveness of magnetic field-line tension in driving the reconnection exhaust [2]. Using the Hybrid-VPIC code, which treats the ions with a particle-in-cell method and employs a simplified fluid model for the electrons, we model current sheets long enough to include the region of meandering ions as well as re-magnetized ions in the far exhaust. The evolution of the ion velocity distributions is analyzed, including both a majority population and a heavier minority ion species (representing, for example, atomic oxygen in the magnetotail). We consider the effect of plasmoids or magnetic islands in the exhaust as well as the possibility of kinetic instabilities driven by the anisotropic ion distributions.

[1] Drake et al., JGR: Space Physics 114(A5) (2009)

[2] Le et al., Physics of Plasmas 21(1) (2014)