ENERGETIC SOLAR PARTICLE DROPOUTS DETECTED BY ULYSSES AT 1.63 AU - A POSSIBLE ENCOUNTER WITH THE EARTHS DISTANT MAGNETOTAIL

Fast solar particles are used to trace the topology of the interplanet ary magnetic field during a solar event detected by the heliosphere in strument for spectra composition and anisotropy at low energy (HISCALE ) on the Ulysses spacecraft on January 2, 1991. Two sharp-edged dropou ts, lasting for 10 and 25 min, were detected in the fluxes of solar io ns from similar to 130 keV to >1.8 MeV and halo (heat flux) electrons from 71-461 eV, while simultaneously the flux of high-energy, 38-315 k eV solar electrons and 56-78 keV ions remained constant. The halo elec trons and 130 keV to >1.8 MeV solar ions are traveling with similar sp eeds, similar to 4 x 10(6) to 3 x 10(7)m/s, much slower than the energ etic solar electrons (>10(8)m/s), and faster than the 56-78 keV ions, suggesting that the dropout field lines were first disconnected from t he Sun and then reconnected, with the distance to the reconnection poi nt and time of the reconnection such that >38 keV electrons had alread y repopulated the dropout field lines. At the time Ulysses was 0.63 AU from the Earth on its way to Jupiter, similar to 2 degrees above the ecliptic with a Sun-Earth-spacecraft angle of similar to 172.8 degrees , approximately where the Earth's magnetotail would be expected to be if it extended to 15,000 Earth radii. We consider the possibility that Ulysses encountered interplanetary field lines connected to the magne totail.