Detailed Kinetic Simulations of Asymmetric Magnetic Reconnection at the Dayside Magnetopause

Abstract:

Unlike symmetric magnetic reconnection, which has been extensively studied over the last decades despite of its rather rareness in space thanks to its relatively intuitiveness, occurrence of strong asymmetric conditions in specific quantities still have to be fully understood. Only recently these new configuration has become of particular interest, mostly in light of the upcoming MMS NASA mission.

In improving this knowldege, this work aim thereby at going deeper into detail on the kinetic properties of asymmetric magnetic reconnection applied to some realistic case, such as the dayside magnetopause. Here, low magnetic field and high density magnetosheath plasma comes in contact with high magnetic field and low density magnetosphere plasma. For now, temperature along both regions is kept constant, as often considered in literature.

Analysis are performed using the fully kinetic implicit code iPIC3D which allows us to go down at electron kinetic levels within an acceptable computational time, as well as considering considerably larger spatial domains. These hallmarks enable us to use this code for multifolds applications, either in space or space industry. However, the presence of strong gradients, such as on plasma density, makes the computational effort even more extreme, though still fully manageable by iPIC3D.

Besided the well-known asymmetric bulges development and the X-line displacement occurring during asymmetric reconnection, one of the first attempt has been to set a very steep gradient to both density and magnetic field outside the current sheet, albeit in compliance of the necessary total pressure balance, simulating thus an eventual intensive and sudden plasma inflow. It is then showns that this particular condition leads to the formation of multiple irregular reconnective points right on the steep gradient. Additionally, marks of electron holes seem to manifest specially along the separatrixes.

Finally, it is doubtless that plenty of physics lies underneath asymmetric conditions. Most of the work done with the symmetric case has to be transposed to these new configurations in order to assess physical behaviors on more realistic conditions, which may lead to completely and unexpected results.