In observations of the quiet Corona with the Ultraviolet Coronagraph Spectrometer (UVCS) on SoHO the line width of the oxygen O VI 1031.9 Å consistently becomes smaller than the width of the O VI 1037.6 Å line at distances beyond 3 Rs. A model is used to show that this difference is due to the pumping of the O VI 1037.6 Å line by the two chromospheric C II lines at 1037 and 1036.3 Å. The model results are compared with two examples from observations to demonstrate that the larger width of the 1037.6 Å line is due to the differing line of sight contributions of the radiative components to each line. This study shows that the O VI linewidth ratio is a valuable diagnostic tool, which when used with the ratio of the intensities of the O VI lines, enables the inference of the outflow velocity of the oxygen ions in the inner corona.
|Cyfnodolyn||Bulletin of the American Astronomical Society|
|Statws||Cyhoeddwyd - 01 Mai 2004|