Interplanetary magnetic field enhancements: Evidence for solar wind dust trail interactions

Abstract

A class of unusual magnetic disturbances has been discovered in which the interplanetary magnetic field increases to a sharp maximum and then decreases almost symmetrically. Initially these were identified as possibly being created by very small comets in the solar wind. However, a significant fraction of them were found to be associated with the passage of the asteroid 2201 Oljato. Since the events occurred when the asteroid was up to 0.5 AU away and not close to the sun-spacecraft line, the process leading to these disturbances must be associated with material in the orbit of Oljato and not Oljato itself. In this paper we update the statistical association of these disturbances with the orbit of 2201 Oljato using data from the latest observing seasons, and discuss the possible mechanisms for causing the disturbances. There are also many interplanetary magnetic field disturbances that are not associated with Oljato. One of these disturbances on October 22, 1980 appears very similar to the disturbance caused by the comet Giacobini-Zinner in the magnetic field, the energetic particles and in the plasma wave disturbances. An examination of the high resolution magnetometer data at the peak of the magnetic disturbance reveals magnetic dips very similar to those observed at Halley and identified with the mirror mode instability. This is further evidence for the comet-like nature of the October 22, 1980 disturbance.