Short answers, pulled from the story.
Michael Faraday first proposed the concept of radiant matter in 1816 during a series of lectures. He expanded on this notion in 1819, listing it among the four states of matter as a purely hypothetical concept. Faraday noted experimental evidence and reasons for belief, likely referring to the strange light he observed in electrical discharges through air and other gases at varying pressures.
Irving Langmuir introduced the term plasma in 1928 to describe ionized gas. The choice of word came from a specific analogy where Lewi Tonks and Harold Mott-Smith recalled that the transport of electrons from thermionic filaments reminded Langmuir of the way blood plasma carries red and white corpuscles and germs. This biological metaphor transformed a description of electrical discharge into a fundamental state of matter.
It is estimated that 99.9% of all ordinary matter in the universe exists as plasma. Stars are almost pure balls of plasma, and the rarefied intracluster medium and intergalactic medium are dominated by this state. Within the Solar System, interplanetary space is filled with the plasma expelled via the solar wind, extending from the Sun's surface out to the heliopause.
Typical lightning discharges 30 kiloamperes at up to 100 megavolts. Plasma temperatures in these events can approach 30,000 kelvin, and electron densities may exceed 10 to the power of 24 per cubic meter. Lightning emits radio waves, light, X-rays, and even gamma rays during these events.
In the mid-1990s, researchers demonstrated that low-temperature atmospheric pressure plasma could effectively inactivate bacterial cells. This work led to the establishment of a new field of research known as plasma medicine. Dielectric barrier discharge became a key tool in this field, allowing for the manipulation of matter without the extreme heat that would destroy biological tissues or delicate materials.
A common quantitative criterion is that a particle on average completes at least one gyration around the magnetic-field line before making a collision. It is often the case that the electrons are magnetized while the ions are not, making magnetized plasmas anisotropic. When used in combination with a high Hall parameter, a critical value triggers the problematic electrothermal instability which limited these technological developments.