Simultaneous observation at sea level and at 5200 m.a.s.l. of high energy particles in the South Atlantic Anomaly

Abstract We compare data obtained by two secondary cosmic ray detectors with different characteristics, located at Mt Chacaltaya, Bolivia (altitude 5200 m) and Niteroi, Brazil (sea level) respectively, separated by a distance of ∼2700 km but both inside the so-called South Atlantic Anomaly (SAA) region, with different magnetic rigidities (cut-offs). A preliminary analysis, made on data obtained in September 2008, clearly shows some common characteristics between the two experiments, such as an increase in the intensity of charged particles from 3 h after sunrise until 1 h after sunset. During this period, the solar magnetic field lines overtake the Earth’s surface. We conclude that in the SAA region and at ground level secondary particles have two origins. The first is from the galactic cosmic rays and the second is from particle precipitation. Other details of these observations, like the relative composition from galactic rays and precipitation, the day/night asymmetry, as well as sunset enhancement, are reported in this paper.