  While magnetic fields have long been considered to be important for the
evolution of magnetic non-degenerate stars and compact stars, it has become
clear in recent years that actually all of the stars are deeply affected. This
is particularly true regarding their internal angular momentum distribution,
but magnetic fields may also influence internal mixing processes and even the
fate of the star. We propose a new framework for stellar evolution simulations,
in which the interplay between magnetic field, rotation, mass loss, and changes
in the stellar density and temperature distributions are treated
self-consistently. For average large-scale stellar magnetic fields which are
symmetric to the axis of rotation of the star, we derive 1D evolution equations
for the toroidal and poloidal components from the mean-field MHD equation by
applying Alfven's theorem, and a conservative form of the angular momentum
transfer due to the Lorentz force is formulated. We implement our formalism
into a numerical stellar evolution code and simulate the magneto-rotational
evolution of 1.5 M$_\odot$ stars. The Lorentz force aided by the $\Omega$
effect imposes torsional Alfven waves propagating through the magnetized
medium, leading to near-rigid rotation within the Alfven timescale. Our models
with different initial spins and B-fields can reproduce the main observed
properties of Ap/Bp stars. Calculations continued to the red-giant regime show
a pronounced core-envelope coupling, which reproduces the core and surface
rotation periods determined by asteroseismic observations.
