Electrostatic plasma oscillations

Figure 3-19. Illustration of electrostatic plasma oscillations distribution of electron density.

Electrostatic Plasma Oscillations Langmuir or Plasma Frequency... 

This electric field makes electrons move back to the left (Fig. 3-19) together with their boundary (at x = xq), whieh results in electrostatic plasma oscillations ... 

This frequency is a measure of the vibration rate of the electrons relative to the ions which are considered stationary. Eor tme plasma behavior, plasma frequency, COp, must exceed the particle-coUision rate, This plays a central role in the interactions of electromagnetic waves with plasmas. The frequencies of electron plasma waves depend on the plasma frequency and the thermal electron velocity. They propagate in plasmas because the presence of the plasma oscillation at any one point is communicated to nearby regions by the thermal motion. The frequencies of ion plasma waves, also called ion acoustic or plasma sound waves, depend on the electron and ion temperatures as well as on the ion mass. Both electron and ion waves, ie, electrostatic waves, are longitudinal in nature that is, they consist of compressions and rarefactions (areas of lower density, eg, the area between two compression waves) along the direction of motion. 

For Oj = He = n 10 cm" and kT 2 eV, Ad 105 nm. If D is a characteristic plasma reactor dimension, then Ad must be plasma oscillations) can develop if the electron collision frequency for elastic collisions is considerably lower than the plasma frequency cOp. Again for the simplest case ... 

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