Determination of vertical plasma drift and meridional wind using the Sheffield University Plasmasphere Ionosphere Model and ionospheric data at equatorial and low latitudes in Brazil: Summer solar minimum and maximum conditions

Abstract

The F region critical frequency foF2 and peak height hmF2, measured simultaneously at the equatorial location Fortaleza (4°S, 38°W, magnetic latitude = 3.5°S) and at the low‐latitude location Cachoeira Paulista (22°S, 45°W, magnetic latitude = 15°S), are compared with their values calculated by the Sheffield University Plasmasphere‐Ionosphere Model (SUPIM) to determine the vertical (E × B) drift velocity at the equator and the magnetic meridional wind velocity over the two locations. The calculated and observed values of foF2 are then matched at both Fortaleza and Cachoeira Paulista to obtain the magnetic meridional winds over their respective conjugate locations. To account for the observed foF2 diurnal variation pattern over Cachoeira Paulista, it was found necessary to include a small source of ionization, attributable to energetic particle precipitation in the South Atlantic anomaly region. The vertical drift velocity and magnetic meridional wind velocity derived for summer months during both solar minimum and solar maximum are compared with their values given by other published models. While the diurnal variation of the modeled vertical drift velocity shows general agreement with the values based on Jicamarca radar measurements (the exception being during the sunset‐midnight period at solar maximum and between 2000–2300 LT at solar minimum), the magnetic meridional wind shows significant differences with respect to the Horizontal Wind Model 1990 (HWM90) [Hedin et al., 1991] during both solar minimum and solar maximum at Fortaleza and at locations conjugate to Fortaleza and Cachoeira Paulista.