Spatial dimensions of coalescing magnetic islands and associated plasma heating
Abstract
Magnetic reconnection is a key fundamental process in collisionless plasmas that converts magnetic energy to plasma kinetic and thermal energies. Past observation and simulation studies suggested that this process causes an efficient energy conversion through the formation and coalescence of multiple magnetic islands. In this study, based on fully kinetic simulations of coalescing multiple islands, we obtained scaling of the spatial dimensions of the internal structure of the coalescing islands. The obtained dimensions in the vertical and horizontal directions depend on the initial thickness of the current sheet and the number of coalescing islands. We also found the scaling of the secondarily forming island near the X-line being different from that of the primary islands. Here the dimension of the internal structure in the vertical direction corresponds to the length of the X-line at the merging points between the coalescing islands. When this length is long enough for ions to be involved, the coalescing process can cause efficient plasma acceleration and heating for both ions and electrons. The obtained scaling successfully predicts the threshold for the ion-involved strong island coalescence.
Spatial dimensions of coalescing magnetic islands and associated plasma heating
Magnetic reconnection is a key fundamental process in collisionless plasmas that converts magnetic energy to plasma kinetic and thermal energies. Past observation and simulation studies suggested that this process causes an efficient energy conversion through the formation and coalescence of multiple magnetic islands. In this study, based on fully kinetic simulations of coalescing multiple islands, we obtained scaling of the spatial dimensions of the internal structure of the coalescing islands. The obtained dimensions in the vertical and horizontal directions depend on the initial thickness of the current sheet and the number of coalescing islands. We also found the scaling of the secondarily forming island near the X-line being different from that of the primary islands. Here the dimension of the internal structure in the vertical direction corresponds to the length of the X-line at the merging points between the coalescing islands. When this length is long enough for ions to be involved, the coalescing process can cause efficient plasma acceleration and heating for both ions and electrons. The obtained scaling successfully predicts the threshold for the ion-involved strong island coalescence.
