Transition region features observed with Hinode/EIS
Abstract
Two types of active region feature prominent at transition region temperatures are identified in Hinode/EIS data of AR 10938 taken on 2007 January 20. The footpoints of 1 MK TRACE loops are shown to emit strongly in emission lines formed at log T=5.4-5.8, allowing the temperature increase along the footpoints to be clearly seen. A density diagnostic of Mg VII yields the density in the footpoints, with one loop showing a decrease from 3x10^9 cm^-3 at the base to 1.5x10^9 cm^-3 at a projected height of 20 Mm. The second feature is a compact active region transition region brightening which is particularly intense in O V emission (log T=5.4) but also has a signature at temperatures up to log T=6.3. The Mg VII diagnostic gives a density of 4x10^10 cm^-3, and emission lines of Mg VI and Mg VII show line profiles broadened by 50 km/s and wings extending beyond 200 km/s. Continuum emission in the short wavelength band is also found to be enhanced, and is suggested to be free-bound emission from recombination onto He^+.
Cite
@article{arxiv.0706.1856,
title = {Transition region features observed with Hinode/EIS},
author = {P. R. Young and G. Del Zanna and H. E. Mason and G. A. Doschek and J. L. Culhane and H. Hara},
journal= {arXiv preprint arXiv:0706.1856},
year = {2015}
}