Controlling factors of the local time extent of magnetopause reconnection: A statistical study

Magnetopause reconnection can occur along X‐lines of variable extent in the direction perpendicular to the reconnection plane. Identifying the spatial extent of X‐lines using satellite observations has critical limitations.

However, we can infer the azimuthal extent of the X‐lines by probing the ionospheric signature of reconnection, the antisunward flow channels across the ionospheric Open‐Closed Field Line Boundary (OCB). We study 39 dayside magnetopause reconnection events using conjugate in situ and ionospheric observations to investigate the variability and controlling factors of the spatial extent of reconnection. We use spacecraft data from Time History of Events and Macroscale Interactions during Substorms (THEMIS) to identify in situ reconnection events.