The coalescence of two parallel current loops in an electron-positron
plasma is investigated by a three-dimensional electromagnetic relativi
stic particle code. Instead of mixing uniformly in the dissipation reg
ion as observed for current coalescence in an electron-ion plasma, ele
ctrons and positrons initially in the loops are driven to move separat
ely by the magnetic gradient drift. Redistribution of the current-carr
ying electrons and positrons creates new current loops, which coalesce
again, if the initial drift velocities remain greater than a critical
value after coalescence. It was found that the energy stored in the c
urrent loops dissipates gradually through several coalescences. Conseq
uently, the electrons and positrons near the current loops are heated
through the coalescence. This process is qualitatively different from
the explosive energy release during coalescence in an electron-ion pla
sma. (C) 1996 American Institute of Physics.