A study of tidal and planetary waves in the American and African sectors

Observed data were obtained from magnetometers measuring the horizontal field intensity H(nT) of the geomagnetic field in the American and African sectors. These magnetometers were located in São José dos Campos, Eusébio, and São Luís, in the American Sector and Tamanrasset, Hermanus, and Tsumeb in the African sector. The datasets were analyzed and periods relating to solar and lunar tidal oscillations were extracted using the least square fit method. Results showed the presence of solar tidal oscillations (diurnal, semidiurnal, and terdiurnal) and semidiurnal lunar tidal oscillations present in both sectors. The latitudinal response of the three solar tidal components at three stations to the sudden stratospheric warming (SSW) of 2018 was also studied. It was observed that the low latitude station nearest the geomagnetic equator presented enhancements in the three components during the event. However, an anomaly was observed in the semidiurnal lunar tide in the African sector which could not be explained. Furthermore, wavelike oscillations between 3 to 32 days and relating to planetary waves were observed in the geomagnetic field. These wavelike oscillations between 3 to 32 days were also seen in the virtual height (h ´F) of the ionosphere measured by ionosondes located at São José dos Campos and Araguatins in the American sector. PW results in the ?H were in good agreement with the F10.7 solar flux. Additionally, during the geomagnetic storm of September 7-11, 2017, ?H component Yariations in the American and African sectors (selected stations) showed different responses suggesting the presence of longitudinal dependence.