IMAGING SPREAD-F STRUCTURES USING GPS OBSERVATIONS AT ALCANTARA, BRAZIL

During October 1994, a dual-frequency GPS receiver was operated in Alc antara, Brazil, at the same site where the Cornell University Portable Radar Interferometer (CUPRI) was performing spread-F measurements for an ongoing rocket campaign. We present data for two nights during whi ch several spread-F plumes drifted through the field-of-view of CUPRI. Fluctuations in the total electron content (TEC) measured with the GP S receiver were correlated with those plumes. We define a ''roughness' ' measure from a specialized high frequency filter. Plots of ''roughne ss'' in a magnetic longitude versus time space show initially low acti vity followed by regions of dramatic localized onsets and a slower sub sequent decline. Features in the roughness image are well-correlated w ith plumes in the CUPRI backscatter power map.