The outer radiation belt during the 10 January , 1997 CME event

On 10 January 1997 a magnetic cloud of a coronal mass ejection impinged upon the earth magnetosphere and caused considerable variations of the relativistic electron population in the earth’s outer radiation belt in the following days. Data obtained with radiation detectors on board a pair of satellites, STRV-1a and STRV-1b in a nearly equatorial geostationary transfer orbit show that the electron flux variations during the days following the arrival of the magnetic cloud can be characterized by four phases during which the fluxes alternatingly decreased and increased. The close relation between flux and Dst variations suggest the magnetic field variations in the inner magnetosphere to play an important role. However, the observed injection of electrons into the trapping region in the morning of 10 January seems to be crucial for the large electron flux enhancement during the afternoon of 10 January.