Density Compressions at Magnetic Switchbacks Associated With Fast Plasma: A Superposed Epoch Analysis

Many magnetic field "switchbacks" were detected by the Parker Solar Probe and their origin remains a puzzle. We did a superposed epoch analysis (SEA) to investigate the plasma characteristics in the vicinity of switchbacks and their radial evolution. SEA is good way to get the statistical average features of certain types of events that have obvious boundaries and different durations. For 55 events ranging from 1 to 30 min, the SEA results show that a small parcel of plasma is piling up in front of the reversed field, and that the trailing plasma density enhancement is much lower. This asymmetry can be explained in part by a fast ejecta and plasma piling up around it. The evolution of events at different distances from the Sun also supports that the switchbacks are related to the faster flow near the Sun. However, these features cannot rule out the possibility that these switchbacks and the related fast flows may be caused by the interchange reconnection near the surface of the Sun.