We present a study of the 2014 January 6 solar energetic particle ( SEP ) event , which produced a small ground level enhancement ( GLE ) , making it the second GLE of this unusual solar cycle 24 .
This event was primarily observed by the South Pole neutron monitors ( increase of { \sim } 2.5 % ) whereas a few other neutron monitors recorded smaller increases .
The associated coronal mass ejection ( CME ) originated behind the western limb and had the speed of 1960 km/s .
The height of the CME at the start of the associated metric type II radio burst , which indicates the formation of a strong shock , was measured to be 1.61 Rs using a direct image from STEREO-A/EUVI .
The CME height at the time of GLE particle release ( determined using the South Pole neutron monitor data ) was directly measured as 2.96 Rs , from the STEREO-A/COR1 white-light observations .
These CME heights are consistent with those obtained for the GLE71 , the only other GLE of the current cycle as well as cycle-23 GLEs derived using back-extrapolation .
GLE72 is of special interest because it is one of the only two GLEs of cycle 24 , one of the two behind-the-limb GLEs and one of the two smallest GLEs of cycles 23 and 24 .