An Etymological Dictionary of Astronomy and Astrophysics

The repulsive interaction due to the → Coulomb energy between two ions. If the ionic charge is Z, then the Coulomb potential energy is Z²e²/a, where a is some typical separation between the ions. The Coulomb pressure is expected to become important when the ratio Γ_C = Z²e²/akT is much larger than 1. In that case, Coulomb effects dominate those of
→ thermal agitation and the gas settles down into a → crystal.

See also: → Coulomb; → pressure.