Dependence of Reconnection Rate and Energy Conversion on the Initial Current Sheet Thickness

Magnetic reconnection is an explosive phenomenon occurring in the space environment, where the magnetic topology is altered and the energy is converted to the plasma. It can account for certain physical processes involved with rapid and massive energy transfer, such as the ones in solar flares and substorm. The term, reconnection rate, is adopted to quantitively estimate the progress of the reconnection. A higher reconnection rate corresponds to a faster reconnection as well as the energy conversion burst. The reconnection rate is sensitive to current sheet configurations and plasma properties, such as the current sheet thickness. From the statistical results of the observations, it is suggested that a thicker current sheet corresponds to a slower ion and electron jets. In this study, we attempt to uncover this relevance by performing theoretical analysis and a series of particle-in-cell (PIC) simulations. Particularly, we focus on the peak reconnection rate as it can reflect the maximum energy conversion rate during the reconnection process. Two types of scaling laws of peak reconnection rate with the current sheet thickness are found, when this thickness increases from the electron-scale to the ion-scale. Our results establish a model to predict the reconnection rate and the energy conversion depending on the current sheet thickness.