Plasma Physics Seminar

Dr. Wally Manheimer Plasma Physics Division, Naval Research Laboratory I've Looked at Clouds from Inside Now - The NRL high-power 94 GHz WARLOC Radar as a Cloud Sensor Gyroklystron development has been reported at APS DPP meetings for years. One of these, a 94 GHz, 100 kW gyroklystron has been incorporated into an NRL radar system called WARLOC, situated on the west shore of Chesapeake Bay. One application of WARLOC has been the study of clouds[1,2]. The added power of the gyroklystron has made possible the rapid resolution of cloud structure with about 10 meter resolution. Images of a variety of clouds have been rapidly acquired. With this fine resolution, it is possible to measure density correlation functions and turbulent spectra, and there are a number of interesting results here which we believe have been obtained for the first time. While there have been many measurements of turbulent spectra in the atmosphere, some with a wide range of wavelength, vitually all (at least with fine resolution) have been in one dimension. WARLOC has to measured turbulent correlation functions with good resolution in 2 dimensions. It confirms that the spectral index is about -5/3 as the Kolmogorov theory predicts, but it also shows that the spectrum is quite anisotropic, in contradiction to one of the principle assumptions of the theory. Furthermore, it shows that unlike mosts fluid instabilities in stratified media (for instance Rayleigh Taylor or Kelvin Helmholtz) , the spectrum is wavelike parallel to the stratification and random perpendicular to it. It has more like a Weibel instability structure, perhaps suggesting that velocity stream lines in clouds attract one another as do current elements in a plasma.