  We present evidence for shock acceleration of cosmic rays to high energies
(about 10 TeV) in the supernova remnant IC 443. X-ray imaging spectroscopy with
ASCA reveals two regions of particularly hard emission: an unresolved source
embedded in an extended emission region, and a ridge of emission coincident
with the southeastern rim. Both features are located on part of the radio shell
where the shock wave is interacting with molecular gas, and together they
account for a majority of the emission at 7 keV. Though we would not have
noticed it a priori, the unresolved feature is coincident with one resolved by
the ROSAT HRI. Because this feature overlaps a unique region of flat radio
spectral index (alpha < 0.24), has about equal light-crossing and synchrotron
loss times, and a power law spectrum with a spectral index of 2, we conclude
that the hard X-ray feature is synchrotron radiation from a site of enhanced
particle acceleration. Evidence against a plerion includes a lack of observed
periodicity (the pulsed fraction upper limit is 33%), the spectral similarity
with the more extended hard region, the location of the source outside the 95%
error circle of the nearby EGRET source, the fact that it is nestled in a bend
in the molecular cloud ring with which IC 443 is interacting, and the
requirement of an extremely high transverse velocity (>5,000 km/s). We conclude
that the anomalous feature is most likely tracing enhanced particle
acceleration by shocks that are formed as the supernova blast wave impacts the
ring of molecular clouds.
