An analytical dynamo solution for large-scale magnetic fields of galaxies

作者：Chamandy Luke^*

来源：Monthly Notices of the Royal Astronomical Society, 2016, 462(4): 4402-4415.

DOI：10.1093/mnras/stw1941

• dynamo
• magnetic fields
• MHD
• galaxies: ISM
• galaxies: magnetic fields
• galaxies: spiral

We present an effectively global analytical asymptotic galactic dynamo solution for the regular magnetic field of an axisymmetric thin disc in the saturated state. This solution is constructed by combining two well-known types of local galactic dynamo solution, parametrized by the disc radius. Namely, the critical (zero growth) solution obtained by treating the dynamo equation as a perturbed diffusion equation is normalized using a non-linear solution that makes use of the 'no-z' approximation and the dynamical alpha-quenching non-linearity. This overall solution is found to be reasonably accurate when compared with detailed numerical solutions. It is thus potentially useful as a tool for predicting observational signatures of magnetic fields of galaxies. In particular, such solutions could be painted on to galaxies in cosmological simulations to enable the construction of synthetic polarized synchrotron and Faraday rotation measure data sets. Further, we explore the properties of our numerical solutions, and their dependence on certain parameter values. We illustrate and assess the degree to which numerical solutions based on various levels of approximation, common in the dynamo literature, agree with one another.

• 出版日期2016-11-11