The Downshift of Electron Plasma Oscillations in the Electron Foreshock Region.
IOWA UNIV IOWA CITY DEPT OF PHYSICS AND ASTRONOMY
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Electron plasma oscillations in the Earths electron foreshock region are observed to shift above and below the local electron plasma frequency. As plasma oscillations shift downward from the plasma frequency, their bandwidth increases and their wavelength decreases. Observations of plasma oscillations well below the plasma frequency are correlated with times when ISEE-1 is far downstream of the electron foreshock boundary. Although wavelengths of plasma oscillations below the plasma frequency satisfy klambdaDe approximately 1, the Doppler-shift due to the motion of the solar wind is not sufficient to produce the observed frequency shifts. A beam-plasma interaction with beam velocities on the order of the electron thermal velocity is suggested as an explanation for plasma oscillations above and below the plasma frequency. Frequency, bandwidth, and wavelength changes predicted from the beam-plasma interaction are in good agreement with the observed characteristics of plasma oscillations in the foreshock region. Originator-supplied keywords include Plasma oscillations Langmuir waves Foreshock.
- Plasma Physics and Magnetohydrodynamics