  We follow two small, magnetically isolated CME-producing solar active regions
(ARs) from the time of their emergence until several days later, when their
core regions erupt to produce the CMEs. In both cases, magnetograms show: (a)
following an initial period where the poles of the emerging regions separate
from each other, the poles then reverse direction and start to retract inward;
(b) during the retraction period, flux cancelation occurs along the main
neutral line of the regions; (c) this cancelation builds the sheared core
field/flux rope that eventually erupts to make the CME. In the two cases,
respectively 30% and 50% of the maximum flux of the region cancels prior to the
eruption. Recent studies indicate that solar coronal jets frequently result
from small-scale filaments eruptions, with those "minifilament" eruptions also
being built up and triggered by cancelation of magnetic flux. Together, the
small-AR eruptions here and the coronal jet results suggest that isolated
bipolar regions tend to erupt when some threshold fraction, perhaps in the
range of 50%, of the region's maximum flux has canceled. Our observed erupting
filaments/flux ropes form at sites of flux cancelation, in agreement with
previous observations. Thus, the recent finding that minifilaments that erupt
to form jets also form via flux cancelation is further evidence that
minifilaments are small-scale versions of the long-studied full-sized
filaments.
