STUDY OF CORONAL TRANSIENTS IN UV LINE EMISSION

We investigate the expected emission from coronal transients in the following spectral lines observable with the Ultraviolet Coronagraph Spectrometer (UVCS) on board SOHO: Hi L 1216 Å, Ovi 1032–1037 Å, Nv 1239–1243 Å, Mgx 610–625 Å, Sixii 499–521 Å, and Fexii 1242 Å. We calculate line intensities and profiles for typical CME conditions, and we analyse their relation with the properties of the perturbed coronal region. We find that significant changes in UV line intensities are produced during a coronal transient. An overall decrease of the Hi L intensity is found, which is mainly due to the Doppler dimming produced by the increase in plasma outflow velocity. The emission from heavy ions is instead mainly affected by variations in plasma density and temperature. We expect to compare these results with the future UVCS observations of coronal transients.