The Role of Resistivity on the Efficiency of Magnetic Reconnection in MHD

Magnetic reconnection is a fundamental plasma process, which can explosively convert magnetic energy to particle energy. When reconnection operates, it releases almost all of the energy stored in the magnetic field to plasma acceleration and heating. The consequences of reconnection depend on the magnetic energy available and the process' ability to rapidly release the energy. Thus, the effectiveness of reconnection, which can be quantified by the rate at which energy is converted, is a key factor in understanding the consequences and implications of this universal process. This paper investigates how the reconnection rate depends on the resistivity in the system. In our fluid-based scheme, resistivity determines the plasma's ability to diffuse across the magnetic field - allowing new magnetic topologies to form. We show that, even when inserting very strong resistive spots with varying shapes, there appears to be a maximum rate of reconnection the system can support. In addition, we find that a sub-optimal choice of resistivity magnitude or shape of the resistive spot leads to lower overall reconnection rates. These results imply that the reconnection rate depends significantly on properties of the diffusion region, even if the size of that region is much smaller than the system.