Observations of stable pickup He+ tori in a magnetic flux rope at 0.85 au
Researchers used Solar Orbiter's STEP instrument to observe stable, torus-shaped velocity distributions of pickup He+ ions embedded in a magnetic flux rope at 0.85 au. They found clear anisotropic signatures consistent with PUI tori rather than scattered shells, suggesting these structures are populated by a large fraction of expected pickup ions under local solar wind conditions.