2015/10/16 by Bhavna Rathore, Rathore, Bhavna, Tiago M. D. Pereira +5 · 1 citation
Physics and Astronomy · #FOS: Physical sciences #History and Developments in Astronomy #Solar and Space Plasma Dynamics #Solar and Stellar Astrophysics (astro-ph.SR) #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.1510.04845
openalex publication_date 2015/10/16 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The C II 133.5 nm multiplet has been observed by NASA's Interface Region\nImaging Spectrograph (IRIS) in unprecedented spatial resolution. The aims of\nthis work are to characterize these new observations of the C II lines, place\nthem in context with previous work, and to identify any additional value the C\nII lines bring when compared with other spectral lines. We make use of wide,\nlong exposure IRIS rasters covering the quiet Sun and an active region. Line\nproperties such as velocity shift and width are extracted from individual\nspectra and analyzed. The lines have a variety of shapes (mostly single-peak or\ndouble-peak), are strongest in active regions and weaker in the quiet Sun. The\nratio between the 133.4 nm and 133.5 nm components is always less than 1.8,\nindicating that their radiation is optically thick in all locations. Maps of\nthe C II line widths are a powerful new diagnostic of chromospheric structures,\nand their line shifts are a robust velocity diagnostic. Compared with earlier\nquiet Sun observations, we find similar absolute intensities and mean line\nwidths, but smaller red shifts; this difference can perhaps be attributed to\ndifferences in spectral resolution and spatial coverage. The C II intensity\nmaps are somewhat similar to those of transition region lines, but also share\nsome features with chromospheric maps such as those from the Mg II k line,\nindicating that they are formed between the upper chromosphere and transition\nregion. C II intensity, width, and velocity maps can therefore be used to\ngather additional information about the upper chromosphere.\n