Kinetic Alfvén Waves Excited in Two-Dimensional Magnetic Reconnection

Kinetic Alfvén waves (KAWs) are believed to be capable of efficiently transporting energy and play an important role in facilitating magnetic reconnection. KAW eigenmode theory suggests that Hall fields can be considered as the components of KAW, providing a mechanism for the generation and dissipation of KAW in magnetic reconnection. Using particle-in-cell simulations, we examined Hall fields in the magnetic reconnection region and found that (1) Hall electric filed is balanced by the ion pressure gradient and (2) the ratio of Hall electric field to Hall magnetic field is on the order of Alfvén speed. These results are consistent with KAW physics. Simulation results also indicate that KAWs are excited in the reconnection site and then transmitted along the separatrices. The wave Poynting flux propagates parallel to the magnetic field lines, carrying substantial energy. It is further found that a thinner current sheet provides a favorable condition for the excitation of KAW and results in a higher ratio of the Hall fields.