Plasma Physics Seminar ( Phys 769)

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.