Line spectra are affected by the motion of plasma particles (electrons, ions, and neutral species). Therefore, by measuring the spectral line shapes, it is possible to deduce such fundamental plasma parameters as temperature and density, as well as more involved characteristics like velocity distributions, presence of electric and magnetic fields, etc.
Thermal broadening (Doppler effect)
This is the simplest mechanism of line broadening, caused by the thermal motion of the light emitting particles.
Electric and magnetic fields
Line spectra are affected by both the external electric and magnetic fields and the field distributions formed by the plasma particles (ions and electrons).
- External macro fields (both electric and magnetic) penetrating into plasma.
- Micro fields produced by the charges of the chaotically moving plasma particles.
- Fields caused by collective phenomena (plasma waves, turbulent motion, etc).
The data derived from the spectral measurements can be very complicated and, usually, there is no straightforward way to infer the plasma parameters directly. Thus, we need to be able to calculate the spectra either analytically or using computer simulations and then compare them to the observed data in order to determine plasma properties.
Modified on: 2010-02-23