The Cessation of Magnetic Reconnection

Abstract. Kinetic simulations of collisionless magnetic re-connection are used to study the effect on the reconnection rate of ion density enhancements in the inflow region. The goal of the investigation is to study a candidate mechanism for the slow-down of magnetic reconnection. The calcula-tions involve either proton or oxygen additions in the in-flow region, initially located at two distances from the cur-rent sheet. Protons are found to be much more tightly cou-pled into the evolution of the reconnecting system and, there-fore, they effect an immediate slowdown of the reconnection process, as soon as the flux tubes they reside on become in-volved. Oxygen, on the other hand, has, within the limits of the calculations, a much less pronounced effect on the recon-nection electric field. The difference is attributed to the lack of tight coupling to the magnetic field of the oxygen popula-tions. Last, a study of proton and oxygen acceleration finds that protons respond primarily to the reconnection electric field, whereas the main oxygen electric field is achieved by Hall-type electric fields at the plasma sheet boundary. Key words. Space plasma physics (magnetic reconnection; numerical simulation studies; numerical simulation studies) 1