## The relation between line ratio and emission measure analyses
^{1} Department of Physics and Astronomy, University of
Glasgow, Kelvin Building, Glasgow, UK^{2} High Altitude Observatory, National Center for
Atmospheric Research^{*}, Boulder, CO 80303, USA
Spectroscopic diagnosis of the temperature and density structure of
hot optically thin plasmas from emission line intensities is usually
described in two ways. The simplest approach, the `line ratio' method,
uses an observed ratio of emission line intensities to determine a
`spectroscopic mean' value of electron temperature
or electron density . The
mean value is chosen to be the theoretical value of
or which matches the
observed value. The line ratio method is stable, leading to well
defined values of or for
each line pair but, in the realistic case of inhomogeneous plasmas,
these are hard to interpret since each line pair yields different mean
parameter values. The more general `differential emission measure'
(
* NCAR is sponsored by the National Science Foundation
## Contents- 1. Introduction and motivation
- 2. Mathematical issues and background
- 3. Relationship between and
- 4. Relationship between and
- 5. Relationship between and , pairs
- 6. Applications
- 7. Summary
- Acknowledgements
- References
© European Southern Observatory (ESO) 1998 Online publication: April 15, 1998 |