Volume 552, April 2013
|Number of page(s)||4|
|Published online||13 March 2013|
Fine structures in the atmosphere above a sunspot umbra
1 Max-Planck Institut für Sonnensystemforschung, 37191 Katlenburg-Lindau, Germany
2 School of Space Research, Kyung Hee University, Yongin, 446-701 Gyeonggi, Korea
Received: 22 November 2012
Accepted: 12 February 2013
We present simultaneous photospheric and chromospheric observations of the trailing sunspot in NOAA 10904, obtained with the Swedish Solar Telescope (SST) La Palma, Canary Islands. Time series of high resolution Ca ii H images show transient jet-like structures in sunspot umbrae are elongated, which we call umbral microjets. These jets are directed roughly parallel to nearby penumbral microjets, suggesting that they are aligned with the background magnetic field. In general, first a bright dot-like structure appears, from which a jet later emerges, although some jets appear without an associated chromospheric dot. Bright photospheric umbral dots are associated with umbral microjets arising in the outer umbra. Nevertheless, a one-to-one correspondence between jet-like events and underlying umbral dots is not seen. They are typically less than 1′′ long and less than 03 wide. The typical lifetime of umbral microjets is around one minute. The brightness of these structures increases from the center of the umbra toward the umbra-penumbra boundary along with the brightness of the local background.
Key words: Sun: chromosphere / Sun: photosphere / sunspots / convection
© ESO, 2013
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.