Abstract
New measurements of the velocities of moving magnetic features (MMFs) are made from spectroheliograms and filtergrams. The sample includes 200 MMFs found in the moats surrounding 7 different sunspots. Our data are compiled with the data from other authors to uncover common properties of moats. The moat radius is roughly twice the penumbral radius. No significant correlation between the average moat velocity or angular extent and any noted property of the spot or moat (size, age, stage of development) is found. Individual MMFs move radially outward with a constant speed, but nearby MMFs may have quite different speeds. The average moat speed is twice the supergranule flow speed. The speed of MMFs in moats is equal on average to the surface gas flow speed. A large bias is found in much of the existing observations of moat speeds from MMFs.
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Brickhouse, N.S., Labonte, B.J. Mass and energy flow near sunspots. Sol Phys 115, 43–60 (1988). https://doi.org/10.1007/BF00146229
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DOI: https://doi.org/10.1007/BF00146229