  In this paper, we study the effects of viscosity on the evolution of double
tearing mode (DTM) in a pair of adjacent Harris sheets based on the resistive
MHD model in the NIMROD code. Similar to the tearing mode in the conventional
single Harris sheet, a transition is observed in the generation of both normal
and monster plasmoids at Pr = 1. In the Pr < 1 regime of DTM, normal plasmoids
(small plasmoids) are generated along with monster plasmoid, whereas in the
single tearing mode (STM) cases such a generation is not observed. When Pr is
above the critical value, the generation of monster plasmoid is halted.
Correspondingly, in the Pr < 1 regime, a quadrupolar flow advects along
poloidal direction, but in Pr > 1 regime this flow advection is inhibited.

Plasma Physics