ANGEO Annales Geophysicae ANGEO Ann. Geophys. 1432-0576 Copernicus Publications Göttingen, Germany 10.5194/angeo-22-3145-2004 Multistation digisonde observations of equatorial spread F in South America Reinisch B. W. 1 Abdu M. 2 Batista I. 2 Sales G. S. 1 Khmyrov G. 1 Bullett T. A. 3 Chau J. 4 Rios V. 5 University of Massachusetts Lowell, 600 Suffolk St., Lowell MA 01854, USA Instituto Nacional de Pesquisas Espaciais, Ave dos Astronautas 1758 C.P. 515 12202-970 Sao Jose dos Campos, SP, Brazil Air Force Research Laboratory, 29 Randolph Road, Hanscom AFB, MA 01731, USA Jicamarca Radio Observatory, Instituto Geofísico del Perú, Apartado 13-0207, Lima 13, Peru University of Tucuman, Av. Independencia 1800, (4000) San Miguel de Tucuman, Argentina 23 09 2004 22 9 3145 3153 Copyright: © 2004 B. W. Reinisch et al. 2004 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://angeo.copernicus.org/articles/22/3145/2004/angeo-22-3145-2004.html The full text article is available as a PDF file from https://angeo.copernicus.org/articles/22/3145/2004/angeo-22-3145-2004.pdf

Directional ionogram and <i>F</i>-region drift observations were conducted at seven digisonde stations in South America during the COPEX campaign from October to December 2002. Five stations in Brazil, one in Argentina, and one in Peru, monitored the ionosphere across the continent to study the onset and development of <i>F</i>-region density depletions that cause equatorial spread <i>F</i> (ESF). New ionosonde techniques quantitatively describe the prereversal uplifting of the <i>F</i> layer at the magnetic equator and the eastward motion of the depletions over the stations. Three of the Brazilian stations were located along a field line with a 350-km apex over the equator to investigate the relation of the occurrence of ESF and the presence of sporadic <i>E</i>-layers at the two <i>E</i>-region intersections of the field line. No simple correlation was found.