Axisymmetric Magnetic Fields Can Be Stably Generated by Simple Convection

抄録

Researchers have struggled to understand the mechanism underlying the formation of celestial magnetic fields. In some studies, the conception of this mechanism, such as Cowling's theorem, which posits that complex convection is necessary to generate a magnetic field, constrains research. Research in this field could progress through the discovery of a simple mechanism. To reveal a possible simple mechanism, this paper addresses generating a magnetic field by convection, which is a simple concept. Whether an axisymmetric poloidal magnetic field can be stably generated by the axisymmetric poloidal convection of a conductive fluid depends on whether the induction term contains a source of power generation. This problem can be solved by decomposing and examining the induction term in detail. Cowling's theory omits certain components (terms) from this term; however, in this study, these components are found to be essential for axisymmetric magnetic field generation on the basis of calculations and examination of the total amount of energy. This approach is a novel concept. In addition, another claim of Cowling's theorem concerning the neutral point is also disputed. Consequently, even under simple axisymmetric convection, the possibility of generating axisymmetric magnetic fields is demonstrated. These findings will contribute to further elucidation of the mechanism of magnetic field formation. However, in this work, unresolved points are found in the maintenance of the magnetic field and the deformation of the formula.