تقرير
In Situ Detection of Strong Langmuir Turbulence Processes in Solar Type III Radio Bursts
العنوان: | In Situ Detection of Strong Langmuir Turbulence Processes in Solar Type III Radio Bursts |
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المؤلفون: | Golla, Thejappa, Macdowall, Robert J, Bergamo, M |
المصدر: | Journal of Geophysical Research. 117(A8) |
بيانات النشر: | United States: NASA Center for Aerospace Information (CASI), 2012. |
سنة النشر: | 2012 |
مصطلحات موضوعية: | Lunar And Planetary Science And Exploration |
الوصف: | The high time resolution observations obtained by the WAVES experiment of the STEREO spacecraft in solar type III radio bursts show that Langmuir waves often occur as intense localized wave packets. These wave packets are characterized by short durations of only a few ms and peak intensities, which well exceed the supersonic modulational instability (MI) thresholds. These timescales and peak intensities satisfy the criterion of the solitons collapsed to spatial scales of a few hundred Debye lengths. The spectra of these wave packets consist of primary spectral peaks corresponding to beam-resonant Langmuir waves, two or more sidebands corresponding to down-shifted and up-shifted daughter Langmuir waves, and low frequency enhancements below a few hundred Hz corresponding to daughter ion sound waves. The frequencies and wave numbers of these spectral components satisfy the resonance conditions of the modulational instability (MI). Moreover, the tricoherences, computed using trispectral analysis techniques show that these spectral components are coupled to each other with a high degree of coherency as expected of the MI type of four wave interactions. The high intensities, short scale lengths, sideband spectral structures and low frequency spectral enhancements and, high levels of tricoherences amongst the spectral components of these wave packets provide unambiguous evidence for the supersonic MI and related strong turbulence processes in type III radio bursts. The implication of these observations include: (1) the MI and related strong turbulence processes often occur in type III source regions, (2) the strong turbulence processes probably play very important roles in beam stabilization as well as conversion of Langmuir waves into escaping radiation at the fundamental and second harmonic of the electron plasma frequency, fpe, and (3) the Langmuir collapse probably follows the route of MI in type III radio bursts. |
نوع الوثيقة: | Report |
اللغة: | English |
DOI: | 10.1029/2012JA017695 |
URL الوصول: | https://ntrs.nasa.gov/citations/20140010437 |
ملاحظات: | NNX12AH47G NNX09AB19G NNG06EO90A NNX08AO02G |
رقم الأكسشن: | edsnas.20140010437 |
قاعدة البيانات: | NASA Technical Reports |
DOI: | 10.1029/2012JA017695 |
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