INDUCTIVE INSTABILITY IN HETEROGENEOUS NONSTATIONARY SYSTEMS

In this study we analyze a new type of electric dynamo caused by the r apid change of the distribution of the electric conductivity in hetero geneous conducting systems. It is demonstrated that there exist two ty pes of electric dynamos, namely, the regular magnetic dynamo and the e lectric current dynamo. The magnetic dynamo is associated with the gro wth of the total energy of the magnetic field. The electric current dy namo is defined as the growth of the total electric current through so me cross section of a conductor, whereby the choice of the cross secti on 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 t he magnetic dynamo, and it can be satisfied even without a hydrodynami c flow. The existence of the hydrodynamic flow is cardinal for the exc itation 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 R eynolds numbers, the laminar magnetic dynamo which is considered in th e present study can be excited at the relatively low magnetic Reynolds numbers Re-m greater than or equal to 1 depending upon the symmetry o f the electromagnetic field. In this study we determined the dependenc e of the magnetic Reynolds number providing the excitation of the inst ability upon the symmetry of the electromagnetic field.