Evidence for a Transition Region Response to Penumbral Microjets in Sunspots
Abstract
Penumbral microjets (PMJs) are short-lived, fine-structured, and bright jets that are generally observed in chromospheric imaging of the penumbra of sunspots. Here we investigate their potential transition region signature by combining observations with the Swedish 1-m Solar Telescope in the Ca ii H and Ca ii 8542 Å lines with ultraviolet imaging and spectroscopy obtained with the Interface Region Imaging Spectrograph (IRIS), which includes the C ii 1334/1335 Å, Si iv 1394/1403 Å, and Mg ii h & k 2803/2796 Å lines. We find a clear corresponding signal in the IRIS Mg ii k, C ii, and Si iv slit-jaw images, typically offset spatially from the Ca ii signature in the direction along the jets: from base to top, the PMJs are predominantly visible in Ca ii, Mg ii k, and C ii/Si iv, suggesting progressive heating to transition region temperatures along the jet extent. Hence, these results support the suggestion from earlier studies that PMJs may heat to transition region temperatures.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2015
- DOI:
- 10.1088/2041-8205/811/2/L33
- arXiv:
- arXiv:1509.01402
- Bibcode:
- 2015ApJ...811L..33V
- Keywords:
-
- sunspots;
- Sun: activity;
- Sun: chromosphere;
- Sun: transition region;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted for publication in the Astrophysical Journal Letters. 6 pages, 5 figures