  We present an overview of the observed properties of the GLEs and those of
the associated flares and CMEs. The solar eruptions are very intense involving
X-class flares and extreme CME speeds (average ~2000 km/s). The active regions
in which the GLE events originate are generally large: 1290 msh (median 1010
msh) compared to 934 msh (median: 790 msh) for SEP-producing active regions.
The initial acceleration of GLE-associated CMEs is much larger (by a factor of
2) than that of ordinary CMEs (2.3 km/s2 vs.1 km/s2). The GLE particle release
is delayed with respect to the onset of all electromagnetic signatures of the
eruptions: type II bursts, low frequency type III bursts, soft X-ray flares and
CMEs. The presence of metric type II radio bursts some 17 min (median: 16 min;
range: 3 to 48 min) before the GLE onset indicates shock formation well before
the particle release. The release of GLE particles occurs when the CMEs reach
an average height of ~3.09 Rs for well-connected events. For poorly connected
events, the average CME height at GLE particle release is ~66% larger (mean:
5.18 Rs). The longitudinal dependence is consistent with shock accelerations
because the shocks from poorly connected events need to expand more to cross
the field lines connecting to an Earth observer. The CME height at metric type
II burst onset is in the narrow range 1.29 to 1.8 Rs, with A mean of 1.53 Rs.
The CME heights at metric type II burst onset and GLE particle release
correspond to the minimum and maximum in the Alfven speed profile. The CME
heights at GLE particle release are in good agreement with those obtained from
the velocity dispersion analysis (Reames, 2009a,b) including the source
longitude dependence. We also discuss the implications of the delay of GLE
particle release with respect to complex type III bursts and hard X-ray
emission.
