  The Sun is already in the declining phase of cycle 24, but the paucity of
high-energy solar energetic particle (SEP) events continues with only two
ground level enhancement (GLE) events as of March 31, 2015. In an attempt to
understand this, we considered all the large SEP events of cycle 24 that
occurred until the end of 2014. We compared the properties of the associated
CMEs with those in cycle 23. We found that the CME speeds in the sky plane were
similar, but almost all those cycle-24 CMEs were halos. A significant fraction
of (16%) of the frontside SEP events were associated with eruptive prominence
events. CMEs associated with filament eruption events accelerate slowly and
attain peak speeds beyond the typical GLE release heights. When we considered
only western hemispheric events that had good connectivity to the CME nose,
there were only 8 events that could be considered as GLE candidates. One turned
out to be the first GLE event of cycle 24 (2012 May 17). In two events, the
CMEs were very fast (>2000 km/s) but they were launched into a tenuous medium
(high Alfven speed). In the remaining five events, the speeds were well below
the typical GLE CME speed (~2000 km/s). Furthermore, the CMEs attained their
peak speeds beyond the typical heights where GLE particles are released. We
conclude that several factors contribute to the low rate of high-energy SEP
events in cycle 24: (i) reduced efficiency of shock acceleration (weak
heliospheric magnetic field), (ii) poor latitudinal and longitudinal
connectivity), and (iii) variation in local ambient conditions (e.g., high
Alfven speed).
