  The nearby Orion-Eridanus superbubble, which was blown by multiple supernovae
several Myr ago, has likely produced cosmic rays. Its turbulent medium, still
energised by massive stars, can impact cosmic-ray transport locally. The gamma
rays produced in cosmic-ray interactions with interstellar gas were used to
compare the GeV to TeV cosmic-ray spectrum in the superbubble and in other
regions near the Sun. We used ten years of Fermi-LAT data in the 0.25-63 GeV
energy range to study the closer (Eridanus) end of the superbubble. We modelled
the spatial and spectral distributions of the gamma rays produced in the
different gas phases of the clouds found in this direction. We found that the
gamma-ray emissivity spectrum of the gas along the outer rim and in a shell
inside the superbubble is consistent with the average spectrum measured in the
solar neighbourhood. This result calls for a detailed assessment of the recent
supernova rate and census of massive stellar winds in the superbubble in order
to estimate the epoch and rate of cosmic-ray production and to constrain the
transport conditions that can lead to such homogeneity and little
re-acceleration. We also found significant evidence that a diffuse cloud lying
outside the superbubble, at a height of 200-250 pc below the Galactic plane, is
pervaded by a 34\% lower cosmic-ray flux, but with the same particle energy
distribution as the local one. Super-GeV cosmic rays should freely cross such a
diffuse atomic cloud without significant loss or spectral distorsion. We
tentatively propose that the cosmic-ray loss relates to the orientation of the
magnetic field lines threading the cirrus, which point towards the halo
according to the dust polarisation data. We gathered past and present
emissivity measurements near the Sun to show how the local cosmic-ray flux
decreases with Galactic height and to compare this trend with model
predictions.
