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arXiv · 2605.27096

Observations of stable pickup He$^+$ tori in a magnetic flux rope at 0.85 au

Chaoran Gu·Lars Berger·Verena Heidrich-Meisner·Erik Jentsch·Robert F. Wimmer-Schweingruber·Lars Seimetz
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Abstract

Interstellar pickup ions originate from the neutral interstellar medium, are ionized in the heliosphere, and picked up by the solar wind. They initially form a torus-shaped velocity distribution function, which is generally believed to be transformed rapidly into an isotropic shell distribution by pitch-angle scattering. With the SupraThermal Electron Proton onboard Solar Orbiter we observe clear torus-shaped velocity distribution functions at an unprecedented one minute resolution. While these tori are variable on a time scale of one minute, they remain stable for over ten hours without signs of significant scattering. We conclude that they are populated by a huge fraction of the expected total number of pick-up ions injected in the past of the same solar wind stream.

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Chaoran Gu, Lars Berger, Verena Heidrich-Meisner, Erik Jentsch, Robert F. Wimmer-Schweingruber, Lars Seimetz. 2026-05-26. Observations of stable pickup He$^+$ tori in a magnetic flux rope at 0.85 au. https://arxiv.org/abs/2605.27096

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