Relativistic Magnetic Reconnection: Magnetic Flux Tubes and Kinks in the Current Sheet

In extreme astrophysical environments, where plasmas are composed of electron positron pairs, the magnetic field energy is often so strong that the process of magnetic reconnection can generate flows that approach the speed of light. The significant energy contained in the magnetic fields is directed to acceleration of particles, heating, and the generation of bulk flows of charged particles via relativistic magnetic reconnection. We have performed a 3D ab initio PIC simulation of relativistic magnetic reconnection, starting from a Harris equilibrium, where most of the energy is in the form of magnetic fields. The movie shows a snapshot of oppositely directed magnetic fields and the associated current sheet after magnetic reconnection has developed. The magnetic field lines are colored by magnitude from weak (purple) to strongest (green), and are separated by a current sheet shown in red. Three key phenomena that occur during this process are highlighted: 1) The current sheet is unstable to kinking shown initially along the direction of the current, 2) the current sheet pinches into an x-point where the magnetic flux reconnects, and 3) flux tubes generated by the reconnected plasma at the center of the current sheet shown at the end of the movie. Although this simulation has a relatively weak magnetic field (~2×107 Gauss), an important question for extremely strong fields approaching the critical quantum Schwinger field (4.4×1013 Gauss) is; when will the magnetic field in the flux tubes become strong enough to generate significant radiation and pair production? The the magnetic field can either be significantly compressed by the inflows, or the flux can expand and weaken due to kinking, as we see for this case with the relatively weak field.

For more information, see Grismayer, T., Schoeffler, K. M., Silva, L. O., Uzdensky, D., Magnetic reconnection with QED effects in near-critical magnetic field, 1st JPP Frontiers in Plasma Physics Conference, Abbazia di Spineto (2017), available here.