Ion dynamics and distribution around comet Halley: Suisei observation

Abstract

Ion dynamics inside the cometosheath of Halley is described based on the plasma observation by Suisei. The pickup shells of water‐group ions and protons of cometary origin are clearly identified. Field line draping around the comet is observed within 2 × 10 5 km of the Halley's nucleus, where magnetic field directions are derived from the symmetry axes of the ion‐pickup shells. Flow turbulence is observed as short‐term (period of ≲ 2min) fluctuations of the anisotropy direction in the outer cometosheath (2‐4.5 × 10 5 km from the nucleus), while the flow is found to be laminar near the closest approach (1.5‐2 × 10 5 km from the nucleus). Spatial distribution of density of water‐group ions (identified up to 4 × 10 6 km from the nucleus) is also presented.