INSTABILITY OF A MAGNETIZED PLASMA-JET

The stability characteristics of a plasma jet V(x) = sech(2) x embedde d in a parallel magnetic field B(x) = B-0 tanh x are investigated. The Kelvin-Helmholtz kink mode, which dominates at small Bo, is stabilize d at B-0 = 0.46, while the pinch mode remains unstable up to B-0 = 0.9 6. Contrary to a nonmagnetized jet, for finite Bo the kink mode satura tes quasilinearly by broadening the jet, such that B-0/V-max becomes l arger than the marginal value 0.46. Including finite resistivity the n onlinear behavior is eventually governed by the tearing mode for all v alues of B-0 not equal 0, consisting of a single plasmoid moving along the jet. Hence the shear flow cannot stabilize the tearing mode, so t hat the apparent tearing stability of resistive current sheets observe d in numerical simulations of magnetic reconnection is only due to fin ite-length effects. (C) 1998 American Institute of Physics. [S1070-664 X(98)01207-5]