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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?

enter image description here

enter image description here

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  • $\begingroup$ These layers form in the air under what conditions? $\endgroup$ – Alex Trounev Dec 7 '19 at 12:22
  • $\begingroup$ It's not air. It's plasma. Ionized gas. This was formed under 23kHz high voltage signal under the pressure range of 500-1000 milliTorr. The voltage is around 20kV with a current of about 60 mA. $\endgroup$ – Indula Munasinghe Dec 7 '19 at 19:13
  • $\begingroup$ What kind of gas is this? $\endgroup$ – Alex Trounev Dec 7 '19 at 19:22
  • $\begingroup$ It is Argon gas. $\endgroup$ – Indula Munasinghe Dec 8 '19 at 11:09
  • $\begingroup$ It looks like a stratified glow discharge, see en.wikipedia.org/wiki/Glow_discharge#/media/… . If you describe the dimensions of the camera, then we can calculate these luminous layers. $\endgroup$ – Alex Trounev Dec 8 '19 at 13:11
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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.

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  • $\begingroup$ Is that the reason plasma glows ? Due to photons created with collisions ? $\endgroup$ – Indula Munasinghe Dec 7 '19 at 19:15
  • $\begingroup$ sorry I defined it wrong, its the electrons that rejoin an ion who emmit photons: In a plasma enough energy gets introduced for the electrons to leave their electron shell. the light is emitted when an electron gets back to an electron shell of an ion, the energy of the emmited photon is the same as the energy that the electron needs to lose to get back to the electron shell. @user17195 $\endgroup$ – Alex bries Dec 7 '19 at 20:05
  • $\begingroup$ Okay. Thank you. $\endgroup$ – Indula Munasinghe Dec 8 '19 at 4:14
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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.

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