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Title:
Generation of auroral kilometric and Z mode radiation by the cyclotron maser mechanism
Authors:
OMIDI, N.; GURNETT, D. A.; WU, C. S.
Affiliation:
AB(Iowa, University, Iowa City, IA) AC(Maryland, University, College Park, MD)
Journal:
Journal of Geophysical Research (ISSN 0148-0227), vol. 89, Feb. 1, 1984, p. 883-895.
Publication Date:
02/1984
Category:
Geophysics
Origin:
STI
NASA/STI Keywords:
AURORAL ZONES, CYCLOTRON RESONANCE, KILOMETRIC WAVES, MASERS, PLASMA-ELECTROMAGNETIC INTERACTION, BROADBAND, DOPPLER EFFECT, ELECTRON DISTRIBUTION, EXPLORER 12 SATELLITE, GYROFREQUENCY
Bibliographic Code:
1984JGR....89..883O

Abstract

The relativistic Doppler-shifted cyclotron resonance condition for EM wave interactions with a plasma defines an ellipse in velocity space when the product of the index of refraction and cosine of the wave normal angle is less than or equal to unity, and defines a partial ellipse when the product is greater than unity. It is also noted that waves with frequencies greater than the gyrofrequency can only resonate with particles moving in the same direction along the magnetic field, while waves with lower frequencies than these resonate with particles moving in both directions along the magnetic field. It is found, in the case of auroral kilometric radiation, that both the upgoing and the downgoing electrons are unstable and can give rise to this radiation's growth. The magnitudes of the growth rates for both the upgoing and downgoing auroral kilometric radiation are comparable, and indicate that the path lengths needed to account for the observed intensities of this radiation are of the order of a few hundred km, which is probably too large. Growth rate calculations for the Z mode radiation show that, for wave frequencies just below the gyrofrequency and wave normal angles at or near 90 deg, the electron distribution is unstable and the growth rates are large enough to account for the observed intensities.

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