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ABSTRACT
Recently, secondary
magnetic island (plasmoid) formation due to the tearing mode
instability of the Sweet-Parker current sheet was observed in numerical
simulations and was suggested as a potential mechanism for increased
reconnection rates. These secondary islands were observed when the
Lundquist Number S is greater
than a specified threshold. Our simulations on a simple representative
geometry (Magnetic Island Coalescence Instability) using a well-tested
pseudo-spectral code, however, show that there is no secondary island
formation or increased reconnection rate if the runs are well-resolved.
The reconnection rate we obtained with such simulations are in
accordance with the Sweet-Parker theory (slow reconnection model:
Reconnection Rate proportional to S1/2)
which is a motivation for high spatial and numerical accuracies needed
in such problems. When we add random noise throughout the simulation
(supported in the recent literature), we do observe secondary island
formation and increased reconnection rates that show a very weak
dependence on the Lundquist Number. Some of these results will be
presented in this talk.
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