Dynamo and Electrical Jet in Hall Plasmas, Application to Astrophysics

Abstract

The magnetic field in Hall plasmas is frozen in the electron component and is advected not only with the plasma motion but also with the electrical current flow. Its coupling with the plasma may be not as strong as characteristic of the MHD approximation. The rotation and slipping of the magnetic field result in a very different and less efficient magnetic field generation by dynamo-rotating plasma disk in magnetic field. We found some exact analytical solutions of nonlinear equations describing the dynamo. In particular, the dynamo may not dissipate the energy in the steady state limit. The 3-component magnetic field and magnetic energy are generated and accumulated during the transition time only. An electrical jet is another unusual phenomenon for MHD. It was investigated theoretically and experimentally for laboratory plasmas during the last 15 years and now is used for fast current switching. We found periodical or shock-like nonlinear wave traveling along a Hall plasma column and not associated with plasma motion. A nonlinear equation describing a possible steady state magnetic field distribution and current flow in a Hall plasma conductor is derived, which differs from the Grad-Shafranov equation. In conclusion we discuss how transfer our results onto astrophysical plasmas. This physics could be important for understanding the evolution of dusty plasma disks and jets around new stars.