  We report the ground-level detection of a Galactic Cosmic-Ray (GCR) flux
enhancement lasting $\sim$ 17 hr and associated with the passage of a magnetic
flux rope (MFR) over the Earth. The MFR was associated with a slow Coronal Mass
Ejection (CME) caused by the eruption of a filament on 2016 October 9. Due to
the quiet conditions during the eruption and the lack of interactions during
the interplanetary CME transport to the Earth, the associated MFR preserved its
configuration and reached the Earth with a strong magnetic field, low density,
and a very low turbulence level compared to the local background, thus
generating the ideal conditions to redirect and guide GCRs (in the $\sim$ 8 to
60 GV rigidity range) along the magnetic field of the MFR. An important
negative $B_Z$ component inside the MFR caused large disturbances in the
geomagnetic field and a relatively strong geomagnetic storm. However, these
disturbances are not the main factors behind the GCR enhancement. Instead, we
found that the major factor was the alignment between the MFR axis and the
asymptotic direction of the observer.
