A 2-DIMENSIONAL MODEL OF MAGNETOHYDRODYNAMICALLY DRIVEN ROTATION OF SPIRAL GALAXIES WITHOUT DARK-MATTER

A steady-state two-dimensional model of the outermost region of a spir al galaxy is presented. The magnetic field, which is able to explain t he flat rotation curve, is calculated, without the existence of any ki nd of dark matter. The vertical and radial distributions of the densit y are calculated, as well as the radial and vertical velocities. The m agnetic field strength is noticeably constant in the peripheral disc, at about 7x10(-7) gauss, much more moderate than that obtained in our previous model (Battaner et al.). The vertical velocities are driven b y Parker's instabilities and induce a moderate escape of gas of about 0.1 M. yr(-1) which prevents excessive flaring.