PROPER MOTION MEASUREMENTS OF UMBRAL AND PENUMBRAL STRUCTURE

Horizontal proper motions of penumbral structure and umbral dots have been measured from a 17-min-long time series of sunspot images by nume rical techniques. In the penumbra, inflows are seen to occur predomina ntly in the inner region, with an average velocity of 290 m s(-1). Pen umbral outflows take place mostly in the outer part, where they reach velocities as high as 1.5 km s(-1), with an average velocity of 500 m s(-1). In the umbra, proper motions of 28 bright dots have been measur ed with an accuracy better than 50 m s(-1). The mean velocity of the u mbral dots is 210 m s(-1). Most of the umbral dots display the well-kn own inward motion away from the peripheral umbra.