Effect of non-uniform magnetic field on the quadrupolar density structure in fast guide field reconnection

Abstract:

In fast guide field reconnection, a quadrupolar density variation in the reconnection plane containing the reconnecting magnetic fields helps in balancing the electric field parallel to the magnetic field in the ion diffusion layer. This parallel electric field plays a crucial role in energy conversion during guide field reconnection. The role of ion drifts in aiding the formation of this quadrupolar density variation is studied in the Magnetic Reconnection eXperiment (MRX). Laboratory conditions are scaled to be similar to space observations of magnetic reconnection (Fox et al., 2018). The normalized guide field, b_gn=b_g/b_up is held at 0.7, where b_g is the guide field at the X-point and b_up is the upstream reconnecting field. Initial analysis shows that the length scale of magnetic field non-uniformity, L_B affects the strength of the quadrupolar density variation in the reconnection plane which in turn can affect the parallel electric field by Ohm’s law. The spatial density profile determined from the ion drifts in the presence of non-uniform magnetic fields is in qualitative agreement with the quadrupolar density variation measured using a Langmuir probe.

Reference

Fox, W., Wilder, F. D., Eriksson, S., Jara-Almonte, J., Pucci, F., Yoo, J., et al. (2018). Energy conversion by parallel electric fields during guide field reconnection in scaled laboratory and space experiments. Geophysical Research Letters, 45, 12,677–12,684. https://doi.org/10.1029/2018GL079883

This work was supported by the Max-Planck Princeton Center for Plasma Physics, funded by the U.S. DoE under contract no. DE-AC0204CH11466.