Astronomy and Astrophysics – Astrophysics – Solar and Stellar Astrophysics
Scientific paper
2011-02-23
ApJ 2011, 730, 113
Astronomy and Astrophysics
Astrophysics
Solar and Stellar Astrophysics
16 pages, 11 figures - Accepted for publication in ApJ
Scientific paper
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 Alfv\'en 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.
Dolla Laurent R.
Zhukov Andrei N.
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