Ionospheric modelling at low latitudes over Brazil during summer solar minimum

Abstract The F-region critical frequency and peak height (foF2 and hmF2, respectively), measured simultaneously at Fortaleza (4° S, 38° W, mag. lat. = 3° S) and Cachoeira Paulista (22° S, 45° W, mag. lat. = 15° S) in Brazil, are compared with values calculated by the Sheffield University Plasmasphere Ionosphere Model to determine the equatorial E×B vertical plasma drift and thermospheric meridional wind of the low-latitude ionosphere. The calculation procedure also allows us to estimate an additional ionization source, that is required to account for the observed diurnal variation of foF2 over Cachoeira Paulista. While the determination of the vertical drift is based on criteria for matching the calculated and observed F-region peak heights over the magnetic equator, the meridional winds over the Brazilian low-latitude region and over its conjugate locations are calculated by comparisons based on the observed and modelled values of hmF2 and foF2. The results presented in this paper are for summer at solar minimum.