Meridional thermospheric winds over Concepción for the 1979–1989 interval derived from ionosonde observations

Abstract

The geomagnetic meridian component of thermospheric neutral winds has been determined for the first time using ionosonde observations made at Concepción (36.8°S;73.0°W) over a decade long interval (January 1979–December 1989). Observations correspond to conditions of low geomagnetic activity (Ap⩽20). Winds have been estimated using a servo theory based algorithm including effects of electric fields. Input values are F-region peak heights determined from ionosonde data. Monthly mean diurnal variations were calculated for every month of the interval so as to estimate month-to-month variability. Then seasonal mean diurnal variations were computed and Fourier components of these variations were derived. Seasonal mean winds clearly show a seasonal dependence and the amplitude of the seasonal mean diurnal variation exhibits seasonal and solar cycle dependencies. Fourier analysis shows that harmonic components are significant up to the terdiurnal one in most cases. Servo winds are found to show little resemblance to winds derived using a well-known empirical model. It is concluded that the seasonal mean diurnal variations have common features with those corresponding to three locations on the Antarctic Peninsula, locations in the same longitude sector. Systematic latitude dependences of winds seem to exist when Concepcion and Antarctic Peninsula winds are combined with lower and higher latitude winds derived from FPI observations. Concepcion winds are also generally similar to those for a location in the northern hemisphere, also in the same longitude sector. Somewhat larger differences are found when compared with those for HWM90.