Dynamo coefficients in Parker unstable disks with cosmic rays and shear

The new methods of estimation

¹ Astronomical Observatory, Jagiellonian University, ul. Orla 171, 30-244 Kraków, Poland e-mail: kowal@oa.uj.edu.pl
² Toruń Centre for Astronomy, Nicholas Copernicus University, 87-148 Piwnice/Toruń, Poland

Received: 7 June 2005
Accepted: 18 July 2005

Abstract

We report a three-dimensional (3D) numerical model of the Parker instability with cosmic rays and shear in a galactic disk and compute the components of the dynamo coefficients α and β from the electromotive forces obtained from simulations. For the first time we apply well-known statistical procedures to fit the modeled electromotive forces in terms of the dynamo tensors. We compare our results with kinematic and other methods of dynamo coefficient estimation. Although we do not solve all problems with the physical interpretation of the dynamo tensors we find that the presented methods give us the ability to compute them with the desired statistical quality. The obtained values of (along the radial direction in galaxy) and are of the order of a few km s^-1 while the value of (along the azimuthal direction) is one or two orders of magnitude smaller.