Supersonic Downflows at the Umbra-Penumbra Boundary of Sunspots - Astrophysics > Solar and Stellar AstrophysicsReportar como inadecuado




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Abstract: High resolution spectropolarimetric observations of 3 sunspots taken withHinode demonstrate the existence of supersonic downflows at or close to theumbra-penumbra boundary which have not been reported before. These downflowsare confined to large patches, usually encompassing bright penumbral filaments,and have lifetimes of more than 14 hr. The presence of strong downflows in thecenter-side penumbra near the umbra rules out an association with the Evershedflow. Chromospheric filtergrams acquired close to the time of thespectropolarimetric measurements show large, strong, and long-livedbrightenings in the neighborhood of the downflows. The photospheric intensityalso exhibit persistent brightenings comparable to the quiet Sun.Interestingly, the orientation of the penumbral filaments at the site of thedownflows is similar to that resulting from the reconnection process describedby Ryutova et al. The existence of such downflows in the inner penumbrarepresents a challenge for numerical models of sunspots because they have toexplain them in terms of physical processes likely affecting the chromosphere.



Autor: Rohan E. Louis, Luis R. Bellot Rubio, Shibu K. Mathew, P. Venkatakrishnan

Fuente: https://arxiv.org/







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