Previous abstract Next abstract

Session 35 - Solar Magnetic Fields.
Display session, Tuesday, June 11
Tripp Commons,

[35.01] Photospheric Surface Flows and Small Magnetic Structures in Sunspot Moats

R. A. Shine, A. Title, Z. Frank (LPARL), G. Scharmer (SSO)

We have computed horizontal flow maps of the photosphere around and within three different sunspots using high spatial resolution continuum movies obtained at the Swedish Vacuum Solar Telescope on La Palma on June 5, 1993, August 29, 1993, and July 14, 1994. Two of the data sets also included magnetograms and dopplergrams. A new feature found in the flow maps is azimuthal structure in the moat flows surrounding sunspots. Instead of a simple radial flow, there are zones of azimuthal divergence and convergence resulting in radial ``spokes'' of convergence. These are not uniformly distinct around the entire circumference but are seen in part of the surrounding area for all 3 sunspots. The angular spacing is about 10 to 20 degrees and the pattern persists for several hours. For one of the sunspots, we have concurrent movies made with a 3 Angstrom wide K line filter. A time average of these images shows bright spokes in the K line congruent with the convergence spokes. Much of the magnetic flux that is continually emerging and moving outward in the moat is in the vicinity of the ``spokes.'' In addition, these data show several good examples of so called ``streakers.'' These are small bright structures seen in continuum movies that appear to be emitted from the outer edge of the penumbral and travel a few thousand km at about 2 to 3 km/s before fading. We find that these are associated with a magnetic field of opposite polarity to the sunspot and that they travel toward another larger and slower moving magnetic feature with the same polarity as the sunspot. When the streaker catches up, it disappears, sometimes coincident with a brightening of the merged feature which continues outward at the previous velocity, about 0.5 km/s.

This work was supported by NSF grant ATM-9213879, NASA contracts NAS8-39746 and NAS8-39747, Lockheed Independent Research Funds, and the Swedish Royal Academy of Sciences.

Program listing for Tuesday