Observations by the Fermi Large Area Telescope (LAT) of nearby interstellar clouds have shown that the $\gamma$-ray emissivities measured per gas atom are fairly uniform within half a kiloparsec of the Sun, except in the Eridu cloud which exhibits a puzzling 30-50% drop in emissivity, hence in cosmic-ray flux. The magnetic field along this atomic filamentary cloud is largely ordered and points towards the halo, so cosmic rays may stream out towards high altitudes below the Galactic plane. To compare with the Eridu cloud, we have studied the $\gamma$-ray flux recorded in another nearby, highly-inclined, magnetically ordered, atomic filament named the Reticulum cloud.

We find a $\gamma$-ray emissivity in the Reticulum cloud that is fully consistent with the local average and that is 40-60% larger than in the similar Eridu cloud. We have studied the gas and magnetic-field states of these two clouds and we have derived estimates of the $\kappa_\parallel$ diffusion coefficient parallel to the magnetic field in the self-confinement scenario where cosmic rays grow Alfvén waves via the streaming instability and those waves are damped by ion-neutral interactions. The smaller $\kappa_\parallel$ values we find in the Eridu cloud challenge its loss of cosmic rays compared to the less diffusive environment of Reticulum.