Modelling X-ray line and continuum emission from comets

The comet C/LINEAR 1999 S4 was observed by the ACIS-S instrument on the Chandra X-ray Observatory (CXO) in July 2000, and the resultant spectrum was by far the clearest cometary X-ray spectrum to date. It is the aim of this paper to see if the spectrum can be reproduced directly from atomic data using the ADAS (the Atomic Data and Analysis Structure) system to try and reproduce the conditions of the comet's interaction with the solar wind. This is accomplished by calculating the atomic rate coefficients for a simplified cometary plasma over a range of likely temperatures and combining the resultant predicted emission line spectrum with a pure bremsstrahlung continuum. The outcome is a model spectrum which can be compared to that Chandra observation.