Electron heating by remagnetization of demagnetized electron beams produced by magnetic reconnection – Theory, simulations, and observations

We show findings that the peak electron temperature downstream of a magnetic reconnection site is associated with electron beams getting remagnetized by the strong reconnected field in regions of compression of the displaced dense current sheet plasma population, known in magnetospheric physics as a dipolarization front. The remagnetized electrons form a ring distribution and we predict its major and minor radii in terms of conditions upstream of the reconnection site, then derive analytical expressions for the electron temperature and the electron temperature anisotropy in terms of the ring major and minor radii in the region of compressed reconnected field. We test the validity of the theory with 2.5-dimension particle-in-cell simulations with varying upstream plasma density and temperature, finding excellent agreement for predicted ring major and minor radii and good agreement for electron temperature and perpendicular electron temperature anisotropy. We show THEMIS satellite observation of the highest electron temperature in a dipolarization front, revealing an electron ring distribution, and we compare the theory to this observation. These results suggest that remagnetization of electron beams could be an important mechanism for heating electrons in reconnection exhausts.