ANGEO Annales Geophysicae ANGEO Ann. Geophys. 1432-0576 Copernicus Publications Göttingen, Germany 10.5194/angeo-31-31-2013 A linear model for amplitude modulation of Langmuir waves in weak electron-beam plasma interaction Baumgärtel K. 1 Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany 04 01 2013 31 1 31 38 Copyright: © 2013 K. Baumgärtel 2013 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://angeo.copernicus.org/articles/31/31/2013/angeo-31-31-2013.html The full text article is available as a PDF file from https://angeo.copernicus.org/articles/31/31/2013/angeo-31-31-2013.pdf

A simple linear approach to the phenomenon of amplitude modulation of Langmuir waves in weak beam plasma interaction is presented. During the short growth phase of the instability and within the longer period after saturation, the waves are described by their linear kinetic dispersion properties.The amplitude modulation appears as result of the beating of waves with different wavelengths and amplitudes that have grown from noise in the initial phase. The Langmuir wave fields are calculated via FFT (fast Fourier transform) technique. The resulting waveforms in temporal representation are quite similar to those observed by spacecraft.

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