Disproof of Cowling's theorem

摘要

Summary form only. In the study of planetary and stellar magnetic fields, a thermally driven MHD generator is generally assumed to be the source of the field. Cowling's theorem is used to prove that cylindrically symmetric models are not capable of producing steady-state magnetic fields. The theorem is based on the fact that there is a current loop that lies inside the conducting medium. This loop has no magnetic field at right angles to the current, and so a current fed by E= nu *B cannot exist. Thus the current loop must decay, and the model must be invalid. The author has demonstrated that mechanisms for feeding a current loop other than the nu *B process can occur. For example, collisional processes can cause a current to migrate into electric-field-free regions.