X-Ray Intensification at Balloon Altitudes of the South Atlantic Magnetic Anomaly in Association with Geomagnetic Activity.

摘要

On April 14 and December 18, 1981, two balloon flights were performed from Sao Jose dos Campos, Brazil (geographic coordinates 23 deg 12'S, 45 deg 51'W and L aprox. 1.13), each carrying an omnidirectional NaI(Tl) scintillation crystal, in order to measure bremsstrahlung X-ray due to energetic electron precipitation in the atmosphere of the South Atlantic Magnetic Anomaly (SAMA), as well as to look for their relationship with geomagnetic activity. Since the April flight occurred during a time interval with an intense geomagnetic activity ((Dst) approx. 290), whereas the December flight was conducted during a geomagnetically calm period ((Dst) < = 35), a comparison between these measurements shows an intensification of about 5 x 10 sup -3 photons/cm sup 2 .sec.KeV at an atmospheric altitude of 5.5 gr/cm sup 2 and for an energy interval of 30-150 KeV. This type of X-rays intensification, observed for the first time at balloon altitudes of the SAMA, is claimed to represent a direct evidence of enhanced energetic electron precipitation in association to the intensification of geomagnetic activity. (Atomindex citation 17:012393)