Prospects for the Crossing by Earth of Comet C/2023 A3 Tsuchinshan-ATLAS’s Ion Tail

Abstract The Earth will pass approximately downstream of the previous position of comet C/2023 A3 (Tsuchinshan-ATLAS) during 2024 October 10–13. We predict that spacecraft at the Sun–Earth Lagrange Point 1, L1, have a significant likelihood to detect pickup ions from the comet, as well as changes in the solar wind associated with the crossing of the comet’s ion tail. Given the Earth’s magnetosphere is also likely to cross the ion tail, it is possible that geomagnetic signatures associated with this will be observed by spacecraft within the magnetosphere and possible at ground-based magnetometers, as observed during Comet 1P/Halley’s apparition in 1910.