Langmuir wave turbulence generated by electromagnetic waves in thelaboratory and the ionosphere

摘要

Summary form only given, as follows. We will present some recentresults of our laboratory experiments at MIT, using a large plasmadevice known as the versatile toroidal facility (VTF). These experimentsare aimed at cross-checking our ionospheric plasma heating experimentsat Arecibo, Puerto Rico using an HF heating facility (heater). Theplasma phenomenon under investigation is the spectral characteristic ofLangmuir wave turbulence produced by ordinary (o-mode) electromagneticpump waves. The Langmuir waves excited by o-mode heater waves at Arecibohave both a frequency-upshifted spectrum and a frequency-downshifted(viz., cascading) spectrum. While the cascading spectrum can be wellexplained in terms of the parametric decay instability (PDI), we haveinterpreted the frequency-upshifted Langmuir waves to be anti-StokesLangmuir waves produced by a nonlinear scattering process as follows.Lower hybrid waves created presumably by lightning-induced whistlerwaves can scatter nonlinearly the PDI-excited mother Langmuir waves,yielding obliquely propagating Langmuir waves with frequencies as thesummation of the mother Langmuir wave frequencies and the lower hybridwave frequencies. This suggested process has been confirmed in ourlaboratory experiments, that can reproduce the characteristic spectra ofLangmuir wave turbulence observed in our Arecibo experiments