The interaction of heavy ions from comet P/Giacobini‐Zinner with the solar wind

The encounter between the ICE spacecraft and Comet P/Giacobini‐Zinner was characterised in the solar wind by intense fluxes of heavy ions, measurable over a region 6 × 10 6 km in extent. The ions are observed with highly anisotropic angular distributions, steep energy spectra, and a change in the energy spectrum at around 80 keV, consistent with a composition predominantly of the water group. Flux versus time profiles follow a general fall off with increasing distance from the comet but with a marked inbound/outbound asymmetry. This asymmetry is due to the higher solar wind velocity on the outbound pass, giving rise to an increased energy gain of the pick‐up ions. The flux versus time profiles are strongly modulated by the rapid changes in the direction of interplanetary magnetic field. We present correlated observations of energetic ions, the interplanetary magnetic field and the solar wind, and compare these observations with theoretical predictions of the ion pick‐up process.