Plasma Frequency

The natural oscillation rate of a plasma's electrons; it sets which waves can propagate.

Disturb a plasma's electrons and they oscillate at the plasma frequency, set by density. It determines which electromagnetic waves a plasma reflects or transmits, which matters for both heating and diagnostics.

The plasma frequency, set by density, decides which electromagnetic waves a plasma reflects and which pass through, governing both heating schemes and diagnostics like interferometry and reflectometry. A wave below the local cutoff is reflected, which is why launch frequency and geometry are chosen so heating power reaches its resonant layer.