Fine structures in the atmosphere above a sunspot umbra
arXiv:1302.2772 · doi:10.1051/0004-6361/201220777
Abstract
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 \ion{Ca}{ii}\, 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\arcsec ~long and less than 0\farcs3 wide. The typical lifetime of umbral microjets is around one minute. The brightness of these structures increases from the center of the umbra towards the umbra-penumbra boundary along with the brightness of the local background.
5 pages, 6 figures. Accepted for publication in A&A Letter
References in corpus (4)
Cited by in corpus (21)
- Solar science with the Atacama Large Millimeter/submillimeter Array - A new view of our Sun
- Fast magnetic reconnection in the solar chromosphere mediated by the plasmoid instability
- Physical Properties of a Sunspot Chromosphere with Umbral Flashes
- Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST)
- The European Solar Telescope
- Vigorous convection in a sunspot granular light bridge
- Heating mechanisms in the low solar atmosphere through magnetic reconnection in current sheets
- Short dynamic fibrils in sunspot chromospheres
- Magnetic reconnection in strongly magnetized regions of the low solar chromosphere
- Onset of secondary instabilities and plasma heating during magnetic reconnection in strongly magnetized regions of the low solar atmosphere
- A Hot Downflowing Model Atmosphere For Umbral Flashes And The Physical Properties Of Their Dark Fibrils
- High Resolution Observations of Chromospheric Jets in Sunspot Umbra
- Umbral chromospheric fine structure and umbral flashes modelled as one: the corrugated umbra
- The formation of small-scale umbral brightenings in sunspot atmospheres
- Stable Umbral Chromospheric Structures
- Multi-Fluid Simulations of Upper Chromospheric Magnetic Reconnection with Helium-Hydrogen mixture
- Spatial Distribution of Origin of Umbral Waves in a Sunspot Umbra
- Downflowing umbral flashes as an evidence of standing waves in sunspot umbrae
- Chromospheric plasma ejection above a pore
- Penumbral brightening events observed in AR NOAA 12546
- Proper Motions of Sunspots' Umbral Dots at High Temporal and Spatial Resolution