Disturbance structures and its magnetic field features in plasma comet tail

The solar wind disturbances result in the emergence of condensation structures in plasma comet tail. Most of them are correlated with plasma vortex flow. In this paper, we analyze the features of condensations basing on the theories of MHD and force-free field. Specifically, we discuss the construction and the distribution of magnetic field and its energy in condensations. We also analyze in detail the coupling process between an unsteady plasma motion and a magnetic field. The coupling effect will let the energy in comet tail change into the force-free field in condensations, so that the magnetic field energy in the condensations increases constantly. Many phenomena observed in comet tail can be explained with the model. (author). 22 refs