Supersonic downflows in the photosphere discovered in sunspot moat regions

T. Shimizu, V. Martinez-Pillet, M. Collados, B. Ruiz-Cobo, R. Centeno, C. Beck, Y. Katsukawa

Stokes measurements of sunspot moat regions were made with a good seeing condition in 2005 July, by using infrared and visible-light Stokes polarimeters (TIP and POLIS) operating at German VTT at Tenerife, Spain. Extremely red-shifted signals are newly found in Stokes V profiles of photospheric lines. The shifted component is located 300-400mA (in Si 10827A) at red side apart from zero velocity wavelength, suggesting existence of supersonic downflows with 8-11 km/s at the photosphere. About 20 events were found in three successive scanning maps of 35 x 45 arcsec field of view. The downflows are seen not only in photospheric Si 10827A line observed by TIP but also in photospheric Fe I 6301.5/6302.5A lines. The size of downflows is in order of less than a few arcsec. This component might be a signature of magnetic reconnection at the photospheric level. Moreover, they might play important role in forming moving magnetic features well observed around sunspots. We expect that such extreme Stokes profiles will be found in higher-resolution Stokes data from Solar-B.

Correspondence

Toshifumi Shimizu (shimizu@solar.isas.jaxa.jp), ISAS/JAXA

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