X-RAY MICROBURSTS IN THE SOUTH-ATLANTIC MAGNETIC ANOMALY

Balloon-borne X ray measurements with high time resolution were carrie d out in the South Atlantic magnetic anomaly to investigate the fine s tructure of the precipitation in this region. Measurements were obtain ed on two balloon flights launched from Cachoeira Paulista, Sao Paulo, Brazil, on January 26 and February 1, 1994, and were supported by onb oard electric field and geomagnetic field ground data. In one flight, we have found that rapid changes do occur in times of about 0.05 s dur ing periods of a few seconds. They should be considered as the first e vidence of the presence of microbursts in the low L value region of th e South Atlantic anomaly. These microbursts were not correlated with s feric signatures in the same hemisphere and may be correlated with mag netic fluctuations in the geomagnetic field. Energy-time features of t he microbursts are examined in order to identify possible responsible mechanisms.