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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 33, issue 11
Ann. Geophys., 33, 1403–1412, 2015
https://doi.org/10.5194/angeo-33-1403-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 33, 1403–1412, 2015
https://doi.org/10.5194/angeo-33-1403-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 11 Nov 2015

Regular paper | 11 Nov 2015

Radar and satellite investigations of equatorial evening vertical drifts and spread F

J. M. Smith1, F. S. Rodrigues1, and E. R. de Paula2 J. M. Smith et al.
  • 1William B. Hanson Center for Space Sciences, The University of Texas at Dallas, Richardson, TX, USA
  • 2Instituto Nacional de Pesquisas Espaciais – INPE, São José dos Campos, SP, Brazil

Abstract. We analyzed pre-midnight equatorial F region observations made by the 30 MHz coherent backscatter radar of São Luis, Brazil between August 2010 and February 2012. These measurements were processed, and used to create monthly maps of the echo occurrence as a function of local time and height. The maps show the inter-annual variability associated with equatorial spread F (ESF) occurrence in the Brazilian longitude sector. We also constructed monthly curves of the evening vertical drifts, for the Brazilian sector, using measurements by the ion velocity meter (IVM) onboard the C/NOFS satellite. The IVM evening drifts show a good overall agreement with the Scherliess and Fejer (1999) empirical model. Measured and model drifts show the development of the pre-reversal enhancement (PRE) of the vertical plasma drifts during ESF season. Using joint radar and satellite measurements, we found that evening (18:00–18:30 LT) mean non-negative drifts provide a necessary but not sufficient condition for the occurrence of topside ESF echoes. Evening downward (negative) drifts preceded the absence of topside ESF irregularities.

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