Geomagnetic phenomena in the South Atlantic anomaly region in Brazil

Abstract

The secular variation in the total geomagnetic field F and the westward drift of South Atlantic magnetic anomaly (SAMA) observed in Brazil during the 20th century are presented. According to the International Geomagnetic Reference Field (IGRF) model for the years 2000 to 2005 the present value of F at São Martinho da Serra (29°.43 S, 53°.80 W) is 22,883 nT, a value close to the measured one. The secular variation in F at this station is −28 nT per year. It is difficult to forecast the drift movement of this anomaly (SAMA) in the coming years, however, it should be a matter of concern should the field continue to decrease at the present rate or even faster. We have also noted that both continuous and impulsive pulsations observed in the H component of the geomagnetic field at São Martinho da Serra are enhanced due to the particle precipitations in the SAMA region. We present here few events observed at São Martinho da Serra showing clear enhancement of the amplitudes of pulsation and discuss the processes for electron precipitation in the atmosphere above SAMA. This justifies the need of a magnetic observatory at São Martinho da Serra not only to monitor the westward drift of the SAMA but also to provide valuable observations for the Space Weather studies at our institute.