On the stability of magnetized rotating jets - The axisymmetric case

The stability of a nonrelativistic, magnetized rotating flow to Kelvin-Helmholtz modes is discussed, using numerical methods for the analysis of the dispersion relation which allow complete and systematic mode classification. In the initial study presented here, attention is restricted to the axisymmetric case, giving sole attention to the vortex-sheet approximation. Major results include (1) interpretation of the reflected modes in terms of negative energy modes; (2) correction of previous results on the route to destabilization of reflected modes; (3) explanation of multiple maxima in the reflection mode growth rate as a function of Mach number; (4) discovery of a new unstable mode for magnetized, nonrotating beams which can be as important as the ordinary mode in a limited Mach number regime; and (5) the derivation of new unstable inertial modes for rotating jets. Some of the astrophysical implications of this study are noted.