JP Michael:
Under what conditions does "light" ionise matter? I haven't researched this at all.
Photoionisation begins with the hydrogen atom, a single electron atom, and is the source of the Lyman Alpha UV spectral line. Multi-electron atoms and molecules can be ionised to various degrees depending on the light energy, going all the way up to gamma radiation. The Lyman Alpha line is at the start of what is referred to as the Vacuum UV wavelengths.
Third, does light maintain ionisation of a plasma without an electric current or electric field present?
Light can be the initiator of the electric and magnetic fields. I think of light, electricity and magnetism as being the Trinity, and I'll one day be continuing my old EM Universe from V2 NIAMI as the OEM, Opto-Elecro-Magnetic Universe. We don't really know what each of these things are, even though we understand their behaviours and effects well enough to do some pretty amazing things with them.
The idea of energy bundles is being looked at, that goes into string and super-string theory, some pretty heavy stuff, so for me I just go with the idea of Aether configurations, motions and relationships. There comes a point where I don't think we will ever or can ever understand the ultimate basic structure of the Universe from a purely scientific, physics standpoint, it gets into metaphysics, the Creators realm. When we get into the hard Gamma 'light' region then mater creation is possible through the pair production phenomena, the proton/anti-proton being produced at GeV energies.
Above certain energies the light can defy the inverse square law, the vacuum itself becomes a non-linear optical medium, and the light will self focus, maybe to infinite distances, so it would be possible for planets or lesser objects, which always have an atmosphere or exosphere containing hydrogen, to have ionised atmospheres even at very great distances from the source.
This article is one of the reasons I decided to proceed with my OEM universe thread:
The Sun Is Stranger Than Astrophysicists Imagined
It’s amazing that we were so spectacularly wrong about something we should understand really well: the sun,” said Brian Fields, a particle astrophysicist at the University of Illinois, Urbana-Champaign.
We just kept finding surprising things,” said Annika Peter of Ohio State University, a co-author of a recent white paper summarizing several years of findings about the solar gamma-ray signal. “It’s definitely the most surprising thing I’ve ever worked on.
https://www.quantamagazine.org/gamma-ra ... -20190501/
The Sun emits far more Gamma rays than previously believed. I won't mention Horace Winfield Webster here

but it's looking to me as though he was on the right track after all. And of course the closer we get to the Sun then the more higher energy gamma rays we would likely find, as they have been attenuated less.
The closer you look into all this, the deeper the rabbit hole gets. I don't think we will ever see the bottom of it. I like Einsteins quote,
The intuitive mind is a sacred gift and the rational mind is a faithful servant. We have created a society that honors the servant and has forgotten the gift.
The physics and mathematics involved with attempting to understand the universe gets to be too much for my rational mind to comprehend, I'm hoping for an intuitive understanding one day.