# Is it possible to create a photon with energy lower than the plasma frequency inside a plasma?

+ 1 like - 0 dislike
454 views

Suppose we have a plasma with corresponding plasma frequency $\omega_{\text{pl}}$. Next, assume that there is some scattering inside the plasma, due to which photons can be created. Is it possible to create a photon with the energy $E < \omega_{\text{pl}}$? Or such process is impossible?

+ 3 like - 0 dislike

Yes, it is possible. Note, a thick plasma at the temperature $T$ radiates all frequencies, like a black body.

answered May 23, 2017 by (132 points)
+ 3 like - 0 dislike

As Vladimir Kalitvianski says, it is very much possible in a microscopic sense. Highly ionized plasma is a soup of charged particles bumping into each other via Coulombic interaction and thus radiating braking radiation all the time. However, once this radiation is created, it does not take long to encounter another charged particle which scatters it in a different direction. As a result, many plasmas can be understood as optically thick below the plasma oscillation frequency - immediately absorbing and reradiating light with a thermal spectrum in random directions.

I.e., plasmas are full of radiation of every frequency chaotically scattering around the place, it is just that ordered electromagnetic waves can arise only as collective plasma oscillations (plasmons) with specific dispersion relations.

answered May 23, 2017 by (1,635 points)

 Please use answers only to (at least partly) answer questions. To comment, discuss, or ask for clarification, leave a comment instead. To mask links under text, please type your text, highlight it, and click the "link" button. You can then enter your link URL. Please consult the FAQ for as to how to format your post. This is the answer box; if you want to write a comment instead, please use the 'add comment' button. Live preview (may slow down editor)   Preview Your name to display (optional): Email me at this address if my answer is selected or commented on: Privacy: Your email address will only be used for sending these notifications. Anti-spam verification: If you are a human please identify the position of the character covered by the symbol $\varnothing$ in the following word:p$\hbar$ysicsOve$\varnothing$flowThen drag the red bullet below over the corresponding character of our banner. When you drop it there, the bullet changes to green (on slow internet connections after a few seconds). To avoid this verification in future, please log in or register.