Multispacecraft Observations of Tailward Propagation of Transient Foreshock Perturbations to Midtail Magnetosheath

Abstract

AbstractWe present three events from multiple spacecraft observations to show that a dayside transient foreshock perturbation associated with an interplanetary magnetic field directional discontinuity can propagate in the midtail magnetosheath and affect the magnetopause. In the first event, perturbations in density and flow were first observed in the dayside foreshock and later in the tail magnetosheath at X ~ −40 RE, a correlation suggests that the foreshock‐originating perturbations propagated to the midtail. The second event shows that foreshock‐originating perturbations were observed in the tail magnetosheath at two radial distances (X ~ −30 and −50 RE) at different times. One plausible explanation for this delay is a tailward propagation of these perturbations along with the directional discontinuity. In the third event, a significant change in the dynamic pressure associated with a foreshock perturbation caused a transient magnetopause outward/inward motion that was first observed on the dayside and later in the midtail at X ~ −55 RE. These events suggest that foreshock perturbations could propagate tailward and continuously affect the nightside magnetopause.