Inductive instability in heterogeneous nonstationary systems

Abstract

In this study we analyze a new type of electric dynamo caused by the rapid change of the distribution of the electric conductivity in heterogeneous conducting systems. It is demonstrated that there exist two types of electric dynamos, namely, the regular magnetic dynamo and the electric current dynamo. The magnetic dynamo is associated with the growth of the total energy of the magnetic field. The electric current dynamo is defined as the growth of the total electric current through some cross section of a conductor, whereby the choice of the cross section is determined by the symmetry of the excited electromagnetic field. We show that the condition for the excitation of the electric current dynamo is less restrictive than the condition for the excitation of the magnetic dynamo, and it can be satisfied even without a hydrodynamic flow. The existence of the hydrodynamic flow is cardinal for the excitation of the magnetic dynamo. In contrast to the turbulent magnetic dynamo which is associated with the fact that magnetic-field lines are ‘‘frozen in’’ to the fluid and thus can be excited at high magnetic Reynolds numbers, the laminar magnetic dynamo which is considered in the present study can be excited at the relatively low magnetic Reynolds numbers Rem>1 depending upon the symmetry of the electromagnetic field. In this study we determined the dependence of the magnetic Reynolds number providing the excitation of the instability upon the symmetry of the electromagnetic field. @S1063-651X~97!03209-1#