Hall magnetohydrodynamic reconnection: The Geospace Environment Modeling challenge

Numerical results are presented on the Geospace Environment Modeling (GEM) reconnection challenge (and its variants) from the Hall magnetohydrodynamics (MHD) code developed at the University of Iowa (UI). Resistivity provides the mechanism for breaking field lines in this study. It is shown that the peak reconnection rate in the quasi-saturated regime is controlled dominantly by ions and has a weak dependence on the resistivity. The reconnection rate is close to those obtained from other particle-in-cell, hybrid, and Hall MHD codes. Some differences between the results from the UI Hall MHD code and other codes are discussed.