SAMA: For how long?



The South Atlantic Magnetic Anomaly (SAMA) has been studied since the beginning of the sixties. This region of low field intensity in the South Adantic near Brazil is known to have important consequences in radiationbelt physics “e.g., Pinto and Gonzalez, 1986”. This feature of the field can be explained by the concept of an eccentric dipole. This concept, specified by the dipole and quadrupole terms of the multipole expansion of the geomagnetic field, account for about 90% of the surface field “Parkinson, 1983”.