  We present a proper motion study of the shock waves within the classic
stellar jet HH 47 based on Hubble Space Telescope H-alpha and [S II] images of
the region taken over two epochs. Individual knots within the jet and in the
bow shock/Mach disk working surface of HH 47A move significantly in the five
years that separate the images, and the excellent spatial resolution of HST
makes it possible to measure the proper motions with enough precision to easily
observe differential motions throughout the flow. The bright portion of the jet
emerges at 37.5 +/- 2.5 degrees from the plane of the sky with an average
velocity of 300 km/s. Dynamical ages of the shock waves in the jet range from a
few decades for knots recently ejected by the source to ~ 1300 years for the
faint extended bow shock HH 47D. The jet curves, but motions of knots in the
jet are directed radially away from the exciting source, and velocity
variability in the flow drives the shock waves that heat the jet internally.
The jet orientation angle varies with time by about 15 degrees, and currently
points to the northwestern portion of a cavity outlined by a reflection nebula,
where a quasi-stationary shock deflects the jet. The major working surface HH
47A is more complex than a simple bow shock/Mach disk, and contains numerous
clumps that move relative to one another with velocities of ~ +/- 40 km/s.
Small clumps or instabilities affect the Mach disk, and dense clumps may move
all the way through the working surface to cause the bumpy morphology seen at
the bow shock. A localized area between the bow shock and Mach disk varies
significantly between the two sets of images.
