Geomagnetic field variations due to Solar and Lunar tides in the Brazilian Sector

<p><strong>Abstract</strong></p><p>Geomagnetic field variations in 2018 due to solar and lunar tides in the Brazilian sector were studied using data provided by magnetometers installed at São José dos Campos (23.21<sup>o</sup>S, 0345.97<sup>o</sup>W; Dip latitude 20.9<sup>o</sup>S), Eusébio, Ceará (3.89° S, 38.46° W) and São Luís, Maranhão (2.53° S, 44.30° W). Variations associated with these tides were identified using the horizontal component of the geomagnetic field, H(nT). Least square fit method was employed in determining the monthly amplitudes and phases of the diurnal, semidiurnal and ter-diurnal solar tides. The monthly amplitudes and phases of the lunar tide were then calculated using the residual measurements (obtained after subtracting the solar tidal components from each day), converting the solar local time to lunar time and subjecting the residuals to harmonic analysis. The maximum solar tide amplitude recorded was 23.96nT(diurnal) in March, at Eusébio whereas the minimum amplitude was 0.45nT(terdiurnal) recorded in December at São José dos Campos. The lunar tide recorded a maximum amplitude of 4.33nT(semidiurnal) in February, at São Luís and a minimum amplitude of 0.13nT(diurnal) in August, at Eusébio.</p><p> </p><p> </p><p><strong>Keywords</strong>: Solar tides, Lunar tides, Geomagnetic field, Magnetometer.</p><p> </p>