Abstract:
During the recent apparition of Comet Halley in 1985-86, a transient ionic event in the form of a blob of H2O(+) emission was recorded in the coma at about 0 h UT on March 13, 1986. Observations were carried out using a special filter for H2O(+) emission at 7000 A/175 A, a 35-cm telescope, a Fabry-Perot interferometer, and an image intensifier camera from Gurushikhar, Mt. Abu. A Fabry-Perot interferogram in H-alpha taken a few minutes later at the same location, reveals strong hydrogen emission (H-alpha) associated with the blob. The velocity field in the blob is structured with relative velocities up to about 35 km/sec. The event is interpreted as arising due to the sector boundary crossing of the interplanetary magnetic field by the comet.
