WISP MOTIONS IN THE CRAB-NEBULA

We present the results of a CCD monitoring campaign of the continuum e mission from the central region of the Crab nebula, amounting to 17 ep ochs spread over 3.5 years. The data provide clear evidence that the b rightest wisps move outward from the pulsar at mildly relativistic vel ocities. This motion, combined with the shape of the wisps, supports t he idea that they arise at a standing shock in an equatorial wind. The deprojected velocity of the wisps in the equatorial plane is less tha n or similar to c/3. We see only small changes in the so-called 'thin wisps' which leads us to suggest that these wisps may be the result of a back-flow from the shock in a toroidal cavity around the pulsar.