Plasmoid identification and statistics in two-dimensional Harris sheet and GRMHD simulations

Animations accompanying a scientific paper with the following title; Plasmoid identification and statistics in two-dimensional Harris sheet and GRMHD simulations, by authors J.T. Vos, H. Olivares, B. Cerutti, and M.A. Mościbrodzka.

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Abstract:
Magnetic reconnection is a ubiquitous phenomenon for magnetized plasma and leads to the rapid reconfiguration of magnetic field lines. During reconnection events, plasma is heated and accelerated until the magnetic field lines enclose and capture the plasma within a circular configuration. These plasmoids could therefore observationally manifest themselves as hot spots that are associated with flaring behaviour in supermassive black hole systems, such as Sagittarius A*. We have developed a novel algorithm for identifying plasmoid structures, which incorporates watershed and custom closed contouring steps. From the identified plasmoids, we determine the plasma characteristics and energetics in magnetohydrodynamical simulations. The algorithm’s performance is showcased for a high-resolution suite of axisymmetric ideal and resistive magnetohydrodynamical simulations of turbulent accretion discs surrounding a supermassive black hole. For validation purposes, we also evaluate several Harris current sheets that are well-investigated in the literature. Interestingly, we recover the characteristic power-law distribution of plasmoid sizes for both the black hole and Harris sheet simulations. This indicates that while the dynamics are vastly different, with different dominant plasma instabilities, the plasmoid creation behaviour is similar. Plasmoid occurrence rates for resistive general relativistic magnetohydrodynamical simulations are significantly higher than for their ideal counterpart. Moreover, the largest identified plasmoids are consistent with sizes typically assumed for semi-analytical interpretation of observations. We recover a positive correlation between the plasmoid formation rate and a decrease in black-hole-horizon-penetrating magnetic flux. These results demonstrate the efficacy of the newly developed algorithm which has enabled an extensive quantitative analysis of plasmoid formation for black hole accretion simulations.