Solitary magnetic structure and sunward flows in the dayside magnetosheath

In this paper, we discuss the changes to the magnetosheath plasma due to interaction with a density structure within the magnetic cloud an interplanetary coronal mass ejection that impacted Earth and caused significant perturbations in plasma boundaries. The bow shock breathing motion is evident due to the changes in the upstream dynamic pressure. A solitary magnetic enhancement forms in the inner magnetosheath with characteristics of a fast magnetosonic shock wave, propagating earthward and perpendicular to the background magnetic field. We show that the magnetosheath plasma is heated twice, during the bow shock crossing and during the interaction with the fast magnetosonic shock inside the magnetosheath. Following these events, a sunward motion of the magnetosheath plasma is evident. Analysis of ion distributions indicates that the sunward flows are caused by the reflection of flux tubes within the fast magnetosonic shock near the magnetopause boundary.