Garcia F, Seilmayer M, Giesecke A, Stefani F
Department of Magnetohydrodynamics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, D-01328 Dresden, Germany.
Phys Rev Lett. 2020 Dec 31;125(26):264501. doi: 10.1103/PhysRevLett.125.264501.
The occurrence of magnetohydrodynamic quasiperiodic flows with four fundamental frequencies in differentially rotating spherical geometry is understood in terms of a sequence of bifurcations breaking the azimuthal symmetry of the flow as the applied magnetic field strength is varied. These flows originate from unstable periodic and quasiperiodic states with broken equatorial symmetry, but having fourfold azimuthal symmetry. A posterior bifurcation gives rise to twofold symmetric quasiperiodic states, with three fundamental frequencies, and a further bifurcation to a four-frequency quasiperiodic state which has lost all the spatial symmetries. This bifurcation scenario may be favored when differential rotation is increased and periodic flows with m-fold azimuthal symmetry, m being a product of several prime numbers, emerge at sufficiently large magnetic field.
在不同旋转的球形几何结构中，当外加磁场强度变化时，通过一系列打破流动方位对称性的分岔过程，可以理解具有四个基本频率的磁流体动力学准周期流的出现。这些流动起源于具有赤道对称性破坏但具有四重方位对称性的不稳定周期和准周期状态。一个后分岔产生具有三个基本频率的二重对称准周期状态，进一步分岔产生一个失去所有空间对称性的四频率准周期状态。当增加差动旋转且在足够大的磁场下出现具有m重方位对称性（m是几个质数的乘积）的周期流时，这种分岔情况可能更有利。
