The WIND-HAARP Experiment: Initial results of high power radiowave interactions with space plasmas (original) (raw)

1998, Geophysical Research Letters

Results from the first science experiment with the new HF Active Auroral Research Program (HAARP) in Alaska are reported. The objective was to study the effects of space plasmas on high power radiowave transmission to high altitudes in the magnetosphere. Reception was done by the NASA/WIND satellite. The data suggest that structured space plasmas along the propagation path impose a power law spectrum of fluctuations on the transmitted waves, resembling scintillations. Because the transmitted waves are near ionospheric plasma frequencies, other types of wave-plasma interactions may occur. Such measurements can provide a new diagnostic tool. Introduction Studies of ionospheric and magnetospheric density irregularities are possible with high frequency (HF) radiowaves. The high latitude auroral region has a wide range of electron density scale sizes generated by plasma instabilities [Keskinen and Ossakow, 1983] and irregularities are observed throughout the polar cap and auroral regions [Rodriguez and $zuszczewicz, 1984]. Such structures are likely sources of scintillation and scattering of HF waves, as shown by fading produced in satellite communication links and ground transmitters [Weber et al., 1986]. Only a few experiments on HF wave scattering from high altitude irregularities have been done [Gurevich et al., 1992], with somewhat controversial results [Greenwald, 1994; Guterich et al., 1994] or with indications that greater detection sensitivity is needed [Hysell et al., 1997]. Previous measurements of wave scattering in space plasmas [Alexander et al., 1979] have suggested the use of spacecraft receivers be-• Naval Research Laboratory, Washington, District of Columbia. 2Air Force Research Laboratory, Hanscom AFB, Massachusetts. 3Advanced Power Technologies, Inc., Washington, District of Columbia.