Magnetic conjugate point observations of kilometer and hundred-meter scale irregularities and zonal drifts



[1] The Conjugate Point Equatorial Experiment (COPEX) campaign was carried out in Brazil, between October and December 2002, to study the conjugate nature of plasma bubble irregularities and to investigate their generation mechanisms, development characteristics, spatial-temporal distribution, and dynamics. In this work we will focus mainly on the zonal spaced GPS (1.575 GHz) and VHF (250 MHz) receivers' data collected simultaneously at two magnetic conjugate sites of the COPEX geometry: Boa Vista and Campo Grande. These GPS/VHF receivers were set up to detect the equatorial scintillations and to measure ionospheric scintillation pattern velocities. Then, the zonal irregularity drift velocities were estimated by applying a methodology that corrects the effects caused by vertical drifts and geometrical factors. The results reveal the coexistence of kilometer- (VHF) and hundred-meter-scale (GPS L-band) irregularities into the underlying depletion structure. Over the conjugate site of Campo Grande, the average zonal velocity at VHF seems to be consistently larger than the estimated GPS velocities until ∼0200 UT, whereas over Boa Vista the irregularities detected from both techniques are drifting with comparable velocities. The hundred-meter-scale structures causing L-band scintillations appear to be drifting with comparable velocities over both the conjugate sites, whereas the kilometer-scale structures are drifting over Campo Grande with larger average velocities (before 0300 UT). Complementary data of ionospheric parameters scaled from collocated digital ionosondes are used in the analysis to explain differences/similarities on the scintillation/zonal drift results.