On the Nature of the Spectral Line Broadening in Solar Coronal Dimmings
Abstract
We analyze the profiles of iron emission lines observed in solar coronal dimmings associated with coronal mass ejections, using the EUV Imaging Spectrometer on board Hinode. We quantify line profile distortions with empirical coefficients (asymmetry and peakedness) that compare the fitted Gaussian to the data. We find that the apparent line broadenings reported in previous studies are likely to be caused by inhomogeneities of flow velocities along the line of sight, or at scales smaller than the resolution scale, or by velocity fluctuations during the exposure time. The increase in the amplitude of Alfvén waves cannot alone explain the observed features. A double-Gaussian fit of the line profiles shows that, both for dimmings and active region loops, one component is nearly at rest while the second component presents a larger Doppler shift than that derived from a single-Gaussian fit.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 2011
- DOI:
- 10.1088/0004-637X/730/2/113
- arXiv:
- arXiv:1102.4745
- Bibcode:
- 2011ApJ...730..113D
- Keywords:
-
- line: profiles;
- Sun: corona;
- Sun: coronal mass ejections: CMEs;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 16 pages, 11 figures - Accepted for publication in ApJ