Behavior of magnetospheric O+ ions during Alfvén wing state

Characterize the behavior of oxygen ions (O+) originating from Earth's magnetosphere during the Alfvén wing state induced by sub-Alfvénic solar wind conditions, including their distributions, dynamics, and interactions along open and closed field lines in the vicinity of the contact between unshocked solar wind, magnetic cloud field lines, and magnetospheric field lines.

Background

Under typical super-Alfvénic solar wind conditions, magnetospheric boundaries such as the bow shock and magnetopause mediate ion transport and acceleration. During rare sub-Alfvénic conditions within a coronal mass ejection's magnetic cloud, Alfvén wings form and fundamentally alter magnetospheric topology.

The paper presents first-of-its-kind Magnetospheric Multiscale (MMS) observations of O+ in this Alfvén wing state, noting bidirectional streaming, escaping O+ into unshocked solar wind, and pitch-angle dispersions. Despite these observations, the authors explicitly state that the overall behavior of magnetospheric O+ under Alfvén wing conditions remains unclear, motivating a precise characterization.