Mechanism of O+ pitch-angle dispersion and asymmetric loss in flux tubes

Ascertain the physical mechanism responsible for the observed pitch-angle dispersion and asymmetric loss in the anti-parallel oxygen ion (O+) flux associated with isolated magnetospheric flux tubes during the recovery phase from the Alfvén wing state, and determine whether kinked flux tube geometry at scales comparable to O+ gyromotion accounts for the dispersion.

Background

During 15:00–15:22 UT, MMS observed multiple isolated convecting flux tubes with O+ enhancements and bidirectional field-aligned distributions. A gradual, asymmetric loss in the anti-parallel O+ flux (pitch-angle dispersion) was identified.

The authors explicitly state that the exact mechanism for this dispersion cannot be definitively determined. They propose a plausible scenario where kinks in the flux tube at scales similar to O+ gyromotion lead to loss into the solar wind, but confirmation is still needed.

References

The exact mechanism of forming the dispersion cannot be definitively determined but the kinked flux tube scenario mentioned above offers one possible explanation for the asymmetric loss in the PAD.

— Observation of O+ Characteristics During the Terrestrial Alfvén Wing State Induced by the April 2023 Coronal Mass Ejection  (2410.21172 - Liang et al., 2024) in Section 3.3