I've been experimenting with cold plasma created by a high voltage source at a frequency of about 23kHz. I observed that sometimes the plasma forms layers within the bulk plasma. Following picture shows what I've observed. Could you explain why this occurs?
Because plasma is charged electric fields accelerate them and magnetic fields steer them in circular orbits, so what i think is happening is that there is some magnetic field, maybe created by the elctric current. See video
edit edit: When an electron gets back to an electron shell it emmits a photon. The energy of the photon is the exact energy that is lost by the electron moving back to a electron shell.
I suspect that it is due to a standing wave. You could test this by moving the electrodes closer together and seeing if the layers move closer together. The layers are too close together to represent 25kHz waves, but could possibly represent a high harmonic of a 25kHz fundamental.