  As supernova remnants expand, their shock waves are freezing in and
compressing the magnetic field lines they encounter; consequently we can use
supernova remnants as magnifying glasses for their ambient magnetic fields. We
will describe a simple model to determine emission, polarization, and rotation
measure characteristics of adiabatically expanding supernova remnants and how
we can exploit this model to gain information about the large scale magnetic
field in our Galaxy. We will give two examples: The SNR DA530, which is located
high above the Galactic plane, reveals information about the magnetic field in
the halo of our Galaxy. The SNR G182.4+4.3 is located close to the anti-centre
of our Galaxy and reveals the most probable direction where the large-scale
magnetic field is perpendicular to the line of sight. This may help to decide
on the large-scale magnetic field configuration of our Galaxy.

Astrophysics