  We investigate the magnetic field evolution in a series of galaxy minor
mergers using the N-body/smoothed particle hydrodynamics (SPH) code
\textsc{Gadget}. The simulations include the effects of radiative cooling, star
formation and supernova feedback. Magnetohydrodynamics (MHD) is implemented
using the SPH method. We present 32 simulations of binary mergers of disc
galaxies with mass ratios of 2:1 up to 100:1, whereby we have additionally
varied the initial magnetic field strengths, disc orientations and resolutions.
We investigate the amplification of a given initial magnetic field within the
galaxies and an ambient intergalactic medium (IGM) during the interaction. We
find that the magnetic field strengths of merger remnants with mass ratios up
to 10:1 saturate at a common value of several $\mu$G. For higher mass ratios,
the field strength saturates at lower values. The saturation values correspond
to the equipartition value of magnetic and turbulent energy density. The
initial magnetization, disc orientation and numerical resolution show only
minor effects on the saturation value of the magnetic field. We demonstrate
that a higher impact energy of the progenitor galaxies leads to a more
efficient magnetic field amplification. The magnetic and turbulent energy
densities are higher for larger companion galaxies, consistent with the higher
impact energy supplied to the system. We present a detailed study of the
evolution of the temperature and the bolometric X-ray luminosity within the
merging systems. Thereby we find that magnetic fields cause a more efficient
increase of the IGM temperature and the corresponding IGM X-ray luminosity
after the first encounter. However, the presence of magnetic fields does not
enhance the total X-ray luminosity. Generally, the final value of the X-ray
luminosity is even clearly lower for higher initial magnetic fields.
