  The Fermi bubbles are part of a complex region of the Milky Way. This region
presents broadband extended non-thermal radiation, apparently coming from a
physical structure rooted in the Galactic Centre and with a partly-ordered
magnetic field threading it. We explore the possibility of an explosive origin
for the Fermi bubble region to explain its morphology, in particular that of
the large-scale magnetic fields, and provide context for the broadband
non-thermal radiation. We perform 3D magnetohydrodynamical simulations of an
explosion from a few million years ago that pushed and sheared a surrounding
magnetic loop, anchored in the molecular torus around the Galactic Centre. Our
results can explain the formation of the large-scale magnetic structure in the
Fermi bubble region. Consecutive explosive events may match better the
morphology of the region. Faster velocities at the top of the shocks than at
their sides may explain the hardening with distance from the Galactic Plane
found in the GeV emission. In the framework of our scenario, we estimate the
lifetime of the Fermi bubbles as $2\times10^6$ yr, with a total energy injected
in the explosion(s) $> 10^{55}$ ergs. The broadband non-thermal radiation from
the region may be explained by leptonic emission, more extended in radio and
X-rays, and confined to the Fermi bubbles in gamma rays.
