Non-axisymmetric magnetohydrodynamic stability of a streaming annular jet containing very dense fluid cylinder and surrounded by a tenuous medium pervaded by a varying azimuthal magnetic field

The magnetohydrodynamic stability of a streaming annular jet containing a very dense fluid cylinder and acted upon by inertial and electromagnetic forces, in the presence of a varying transverse magnetic field pervading a tenuous surrounding medium, is considered. A general dispersion relation is established and studied analytically, and the results are confirmed numerically. The magnetic fields are stabilizing or destabilizing for each of the symmetric (m = 0) and non-axisymmetric (m ≠ 0) modes under some restrictions. The streaming has a strong destabilizing character, and its influence is to enlarge the magnetohydrodynamic instability domains and shrink the stability domains. The thicker the dense fluid core, the greater the number of magneto-hydrodynamically stable states. Increasing the magnetic field intensity shrinks the unstable domains. The (in)stability situation is much worse for m ≠ 0. However, if the axial field intensity is sufficiently high and greater than the transverse field intensity, the destabilizing character of the model, in a few cases, may be suppressed. This occurs if the Alfvén-wave velocities interior and exterior to the annular jet are greater than the unperturbed fluid velocity.