A simulation study of generation of field‐aligned currents and Alfvén waves by three‐dimensional magnetic reconnection

Abstract

We have carried out a three‐dimensional compressible MHD simulation to study the generation of field‐aligned currents (FACs) and Alfvén waves by magnetic reconnection without and with an initial guide magnetic field (By). For By = 0, two pairs of FACs are generated on each side of current sheet. The polarities of the resulting FAC pair in the leading bulge region are opposite to those of the FAC pair in the trailing quasi‐steady region. It is further found that a large portion of FACs (∼ 40%) is located in the closed field line region. For nonzero By cases, FACs existing in the initial current sheet are redistributed by the magnetic reconnection process. The inertia term is mainly responsible for the redistribution. The results indicate that the presence of IMF By leads to a shift of the reversal site between the downward and upward field‐aligned currents that may contribute to the observed region 1 field‐aligned currents near noon in the polar ionosphere. The Walén relation between FAC and parallel vorticity is examined. Implications for observations are discussed.