Thin layer axion dynamo

Abstract: We study interacting classical magnetic and pseudoscalar fields in frames of the axion electrodynamics. A large scale pseudoscalar field can be the coherent superposition of axions or axion like particles. We consider the evolution of these fields in a thin spherical layer. Decomposing the magnetic field into the poloidal and toroidal components, we take into account their symmetry properties. The dependence of the pseudoscalar field on the latitude is accounted for the induction equation. Then, we derive the dynamo equations in the low mode approximation. The nonlinear evolution equations for the harmonics of the magnetic and pseudoscalar fields are solved numerically. As an application, we consider a dense axion star embedded in solar plasma. The behavior of the harmonics and their typical oscillations frequencies are obtained. We suggest that such small objects consisting of axions and confined magnetic fields can cause the recently observed flashes in solar corona contributing to its heating.