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Author Hansen, Shirley F.
Sponsorship USDOE
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Publisher American Geophysical Union
Language English
Subject Keyword PHYSICS ♦ ANGULAR DISTRIBUTION ♦ BREMSSTRAHLUNG ♦ CYCLOTRON RADIATION ♦ DISTRIBUTION ♦ EARTH ♦ ELECTRIC DISCHARGES ♦ ELECTROMAGNETIC WAVES ♦ ELECTRONS ♦ EMISSION ♦ FREQUENCY ♦ MAGNETIC FIELDS ♦ PLASMA ♦ RADIATION BELTS ♦ RADIATIONS ♦ RADIO WAVES ♦ RESONANCE ♦ SPECTRAL SHIFT ♦ VELOCITY ♦ WHISTLERS
Abstract It was shown that some types of v-l-f emissions (hooks, risers, and falling tones) may be the result of cyclotron emission by energetic electrons trapped in the earth's magnetic field. Observational evidence suggests that a relatively intense electromagnetic whistler-mode wave may be necessary to trigger each such emission. An interaction mechanism is proposed by which certain electrons may couple with a wave already propagating along the same line of force. A gyroresonance is established that organizes the electrons so that cyclotron radiation can be coherent. A change in phase relation occurs for those electrons that have a longitudinal velocity component such that the Doppler-shifted frequency of the whistler wave seen by the electron is equal or nearly equal to the electron gyrofrequency. This condition is met by electrons moving in a direction opposite to the whistler wave and is satisfied only over a certain fraction of the line of force. Observations also show instances of a sudden change in slope of the rising tail of a hook or other v-l-f emission at the crossing of the spectrums of the emission and a whistler. This change is interpreted as the effect of the encounter of a whistler with the electron stream that changes both energy and pitch angle of the emitting electrons. (auth)
ISSN 01480227
Educational Use Research
Learning Resource Type Article
Publisher Date 1963-11-01
Publisher Department National Bureau of Standards, Boulder, Colo.
Journal Journal of Geophysical Research
Volume Number 68
Issue Number 21
Organization National Bureau of Standards, Boulder, Colo.


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