Extreme Magnetopause Deformation Induced by High‐Speed Jet From Foreshock Transient

Abstract This study presents comprehensive observations of intense high‐speed jets (HSJs) and their global impacts on the inner magnetosphere and ionosphere, using multi‐satellite and ground‐based observations. Cluster‐4, located near the bow shock, observed signatures associated with foreshock transients generated by a solar wind directional discontinuity. Downstream of the bow shock, THEMIS‐A, positioned post‐noon (∼12.8 MLT) in the magnetosheath, detected a sunward plasma flow prior to crossing into the magnetosphere. Nearly simultaneously, THEMIS‐E, inside the magnetosphere at ∼13.4 MLT, suddenly crossed into the magnetosheath and observed intense earthward HSJs. The strong compression of the magnetopause current sheet forced GOES‐13 to temporarily enter the magnetosheath, while SuperDARN radars registered enhanced poleward ionospheric convection and magnetometers detected signatures of westward currents. These sequential observations provide a rare, integrated demonstration of how an upstream foreshock disturbance transfers energy and momentum throughout the coupled magnetosphere‐ionosphere system.