ionizedgas
Ionized gas, or plasma, is a state of matter in which a significant fraction of atoms have lost electrons, creating positive ions and free electrons. Because of these free charges, the gas conducts electricity and responds collectively to electromagnetic fields. Ionized gas can be fully ionized, with most atoms stripped of electrons, or partially ionized, with a mix of ions and neutral atoms.
Ionization occurs when energy input exceeds binding energies: by photons (photoionization) from hot stars or active
Plasma properties include high electrical conductivity, long-range electric and magnetic interactions, Debye shielding, and plasma frequency;
Observationally, ionized gas emits characteristic spectral lines such as H-alpha, [O III], [N II], and He II,