Abstract Magnetic reconnection occurs continuously along long X‐lines at the Earth's magnetopause. The maximum magnetic shear model predicts the locations of these long X‐lines for a wide range of upstream solar wind conditions. One of the more perplexing observational results is that these X‐lines appear to be stationary, even in the presence of significant magnetosheath plasma bulk flow. A scenario is developed whereby an X‐line forms at the location predicted by the maximum magnetic shear model, but then immediately propagates with the magnetosheath plasma bulk flow away from this location. Before this X‐line can travel far, a new X‐line forms at the location of the original X‐line. If the X‐line reformation cadence is high enough, then these multiple, propagating X‐lines could appear as a single, quasi‐stationary X‐line. One observational test of this scenario is that a spacecraft crossing the magnetopause poleward of the original X‐line location would always observe multiple X‐lines. Magnetospheric Multiscale observations are used to perform this observational test. Results show that there are multiple X‐lines near the predicted location of the X‐line and therefore, this scenario may have merit.
Fuselier et al. (Sun,) studied this question.