Numerical studies on the link between radioisotopic signatures on Earth
  and the formation of the Local Bubble. I. 60Fe transport to the solar system
  by turbulent mixing of ejecta from nearby supernovae into a locally
  homogeneous ISM
  The discovery of radionuclides like 60Fe with half-lives of million years in
deep-sea crusts and sediments offers the unique possibility to date and locate
nearby supernovae. We want to quantitatively establish that the 60Fe
enhancement is the result of several supernovae which are also responsible for
the formation of the Local Bubble, our Galactic habitat. We performed
three-dimensional hydrodynamic adaptive mesh refinement simulations (with
resolutions down to subparsec scale) of the Local Bubble and the neighbouring
Loop I superbubble in different homogeneous, self-gravitating environments. For
setting up the Local and Loop I superbubble, we took into account the time
sequence and locations of the generating core-collapse supernova explosions,
which were derived from the mass spectrum of the perished members of certain
stellar moving groups. The release of 60Fe and its subsequent turbulent mixing
process inside the superbubble cavities was followed via passive scalars, where
the yields of the decaying radioisotope were adjusted according to recent
stellar evolution calculations. The models are able to reproduce both the
timing and the intensity of the 60Fe excess observed with rather high
precision, provided that the external density does not exceed 0.3 cm-3 on
average. Thus the two best-fit models presented here were obtained with
background media mimicking the classical warm ionised and warm neutral medium.
We also found that 60Fe (which is condensed onto dust grains) can be delivered
to Earth via two physical mechanisms: either through individual fast-paced
supernova blast waves, which cross the Earth's orbit sometimes even twice as a
result of reflection from the Local Bubble's outer shell, or, alternatively,
through the supershell of the Local Bubble itself, injecting the 60Fe content
of all previous supernovae at once, but over a longer time range.
