Redshift caused by plasma and more

[JP Michael]

JP Michael

Or could these just be scientific weasel words for the same phenomenon?

I agree with antosarai on this.
The term "redshift" in astronomy refers to the position of spectral lines of particular elements found to be not in their normal position but "shifted" toward the red end of the spectrum, or also possibly "shifted" toward the blue end of the visible light spectrum.
"Redshift" does not refer to the changing of the visible color of light as it passes through more of earths atmosphere at sunset. it is a different phenomenon.
Jack

Cheers Jack. I found a couple of papers which might assist me in my understanding of this:

F. Zagury and F. Goutail, "Spectral analysis of extinguished light," New Astronomy 8(6), 2003: 537-548.
F. Zagury and M. Fujii, "Spectral analysis of red-scattered sunlight at sunrise," New Astronomy 8(6), 2003: 549-556.

Contrary to what seems to be indicated by their shape a blue continuum followed by a red bump— spectra of a glow horizon are not simply the sum of scattered sunlight by two media (or two different kind of particles) on the same line of sight.
The reddest (lowest altitudes) spectra of a glow horizon are due to sunlight extinguished by the gas (Rayleigh extinction ozone absorption) in the outermost parts of the atmosphere and scattered—still by the gas (mainly nitrogen)—in the direction of the observer. Extinction of the scattered light by the gas can also happen but should be a minor effect. In any case, this will not change the analytical expression of the fit.

Although I found this comment interesting:

There are striking similarities between the spectra presented here and the spectra of some red nebulae, the best example being spectra in Orion observed by Perrin and Sivan (1992). It is currently admitted that the red color of these nebulae must result from an emission process. The example of the red horizon suggests the possibility of other explanations for the red color of these nebulae.