Chau Chong Shing, Jorge LuisWoodman Pollitt, Ronald Francisco2016-10-252017-12-212016-10-252017-12-212001Chau, J. L., & Woodman, R. F. (2001). Interferometric and dual beam observations of daytime spread-F-like irregularities over Jicamarca.==$Geophysical Research Letters, 28$==(18), 3581-3584. https://doi.org/10.1029/2001GL013404index-oti2018http://hdl.handle.net/20.500.12816/515We report new observations made on April 11 2000 over Jicamarca of daytime spread-F-like irregularities. These irregularities are extremely rare (this was the fourth observation in the history of Jicamarca) and were first reported by Woodman et al. [1985]. The main features of these new observations, which are similar to the previous ones, are that they were: (1) two orders of magnitude stronger than the incoherent scatter echoes at the F peak, (2) observed between 1400 and 1600 LT; (3) characterized by small Doppler shifts (vd < 1 m s-1); and (4) characterized by long correlation times, i.e., narrow spectral widths. The latter is interpreted as evidence that these irregularities are field aligned (very aspect sensitive in the north-south direction). On this occasion the irregularities occurred at higher altitudes than before, between 950 and 1450 km compared to 600-1000 km. The echoes in these recent observations were quite localized in the east-west direction (they were much stronger in the west beam than in the east beam). Furthermore, using interferometry we determined that the echoes were aspect sensitive in the east-west (as well as north-south) direction with aspect angle widths as small as 0.2 degrees, particularly when the echoes were strong.application/pdfenginfo:eu-repo/semantics/openAccessInterferometryF RegionPlasmaRegion EJicamarca Radio Observatoryinfo:eu-repo/semantics/preprinthttp://purl.org/pe-repo/ocde/ford#1.05.01Geophysical Research Lettershttps://doi.org/10.1029/2001GL013404