  This paper updates the influence of environmental and source factors of
shocks driven by coronal mass ejections (CMEs) that are likely to influence the
solar energetic particle (SEP) events. The intensity variation due to CME
interaction reported in [1] is confirmed by expanding the investigation to all
the large SEP events of solar cycle 23. The large SEP events are separated into
two groups, one associated with CMEs running into other CMEs, and the other
with CMEs running into the ambient solar wind. SEP events with CME interaction
generally have a higher intensity. New possibilities such as the influence of
coronal holes on the SEP intensity are also discussed. For example, the
presence of a large coronal hole between a well-connected eruption and the
solar disk center may render the shock poorly connected because of the
interaction between the CME and the coronal hole. This point is illustrated
using the 2004 December 3 SEP event delayed by about 12 hours from the onset of
the associated CME. There is no other event at the Sun that can be associated
with the SEP onset. This event is consistent with the possibility that the
coronal hole interaction influences the connectivity of the CMEs that produce
SEPs, and hence the intensity of the SEP event.
