Magnetohydrodynamic instabilities can be responsible for the formation ofstructures with various scales in astrophysical jets. We consider the stabilityproperties of jets containing both the azimuthal and axial field of subthermalstrength. A magnetic field with complex topology in jets is suggested bytheoretical models and is consistent with recent observations. Stability isdiscussed by means of a linear analysis of the ideal magnetohydrodynamicequations. We argue that in azimuthal and axial magnetic fields the jet isalways unstable to non-axisymmetric perturbations. Stabilization does not occureven if the strengths of these field components are comparable. If the axialfield is weaker than the azimuthal one, instability occurs for perturbationswith any azimuthal wave number $m$, and the growth rate reaches a saturationvalue for low values of $m$. If the axial field is stronger than the toroidalone, the instability shows for perturbations with relatively high $m$.
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机译：磁流体动力学不稳定性可能是导致天体物理射流中各种尺度结构形成的原因。我们考虑了包含热强度的方位角和轴向场的射流的稳定性。理论模型提示了喷射器中具有复杂拓扑的磁场，该磁场与最近的观测结果一致。通过对理想磁流体动力学方程的线性分析来讨论稳定性。我们认为，在方位角和轴向磁场中，射流对于非轴对称扰动总是不稳定的。即使这些现场组件的强度可比，稳定性也不会发生。如果轴向场弱于方位角场，则对于任何方位角波数$ m $的扰动都会发生不稳定性，并且对于$ m $的低值，增长率达到饱和值。如果轴向场强于环面波，则对于$ m $较高的扰动，将显示不稳定性。
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