Magnetized outflows are subject to a variety of instabilities. These can be classified to pressure driven, Kelvin-Helmholtz, and current driven instabilities.
Pressure driven instabilities are related to the interplay(相互作用，相互影响) between the gas pressure and the curvature of magnetic field lines. They are relevant close to the launching region of the outflow and may be important as long as the outflow is still subsnoic.
Kelvin-Helmholtz (KH) instabilities arise from velocity gradients in the flow and may be important in the shearing layer between the outflow and the external medium. KH instabilities have been extensively studied and are becoming most dangerous in the region beyond the Alfven point but still sub-fast magnetosonic point.
Current driven (CD) instabilities have received much less attention but are the most relevant ones for Poynting-flux dominated outflow, since they can convert the bulk Poynting flux into radiation and kinetic energy of the fow. Among the CD instabilities the m=1 kink instability is generally the most effective.
(From: astro-ph/0601172 )
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