Energetic oxygen ions in the magnetosheath in the negative BZ phase of the CME on January 10, 1997 Original Research Article

Energetic oxygen ion flux intensifications were observed by the HEP/LD instrument on board the GEOTAIL satellite thoughout the Bz negative phase of the CME event on January 10, 1997. At this time, the spacecraft was moving in the magnetosheath at 1500 LT on a magnetopause skimming segment of its orbit. The very steady southward magnetic field in the magnetosheath (negative Bz of the CME) was highly inclined forming an angle of 45° with respect to the north direction. The observed oxygen enhancements in the magnetosheath show anisotropic angular distributions which occupy a varying fraction of the unit sphere. These distributions became particularly narrow during the passage of a solar wind pressure pulse between between 1050 and 1113 UT. The details of the angular distributions in the magnetosheath favour a leakage model, although the reconnection model cannot be denied.