Simultaneous entry of oxygen ions originating from the Sun and Earth into the inner magnetosphere during magnetic storms

Abstract

The aim of this paper is to present, for the first time, almost simultaneous enhancements of both low‐ and high‐charge‐state oxygen ions in the inner magnetosphere during magnetic storms. Storm‐time enhancements of low‐charge‐state O ions are well recognized, but the behavior of high‐charge‐state O ions is less known. Data simultaneously collected from the ACE, Geotail, and Polar satellites indicate the following: (1) In the inner magnetosphere (at L = 3–5), the number density of high‐charge‐state O ions was increased during the early phase of magnetic storms (Polar). (2) No corresponding enhancements were identified in the number density of O ions observed in the solar wind (ACE) and the near‐Earth magnetotail (Geotail). (3) The number density of high‐charge‐state O ions present in the near‐Earth magnetotail was considerably lower than in the solar wind and the inner magnetosphere. We calculated trajectories of O6+ ions under electric and magnetic field models. The O6+ ions that became observable in the energy window of Polar were transported from the high‐latitude magnetopause to the inner magnetosphere when the convection electric field was strong. When the convection electric field was weak, the ions were reflected toward the distant tail. The O6+ ions that became observable in the energy window of Geotail were sufficiently transported from the low‐latitude magnetopause to the near‐Earth magnetotail regardless of the strength of the convection electric field. The observational facts may be adequately explained in terms of ion transport paths depending on the convection electric field with different entry points.