  Magnetic reconnection is a ubiquitous phenomenon for magnetized plasmas 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 behavior in supermassive black hole systems, such as Sagittarius
A$^\ast$. 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 behavior is similar. Plasmoid occurrence
rates for resistive general relativistic magnetohydrodynamical simulations are
significantly higher than for the 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. The developed algorithm has
enabled an extensive quantitative analysis of plasmoid formation in black hole
accretion simulations.
