LAUSR

This study reports an extreme ionospheric plasma depletion event over the Eastern Pacific from postmidnight to early morning during the superstorm's recovery phase on 21 November 2003 observed by the DMSP F13, ROCSAT‐1, GRACE, and CHAMP satellites, and two ground‐based GPS receivers. The depletion and its interhemispheric geomagnetic conjugate effect occurred between ∼40°S and 40°N geomagnetic latitudes. This suggests a possible extremely long‐range flux tube connection with an apex altitude exceeding 6,000 km over the geomagnetic equator. Notably, the observed altitude for midlatitude depletions of equatorial origin in the morning is the highest ever reported. Previous studies have primarily observed the extension of equatorial plasma bubbles to middle latitudes in the post‐sunset hours. The continuous upward vertical plasma drift, supported by ROCSAT‐1 and TIE‐GCM simulations, may drive the unprecedentedly strong latitudinal extension of these midlatitude plasma depletions in the midnight‐to‐morning sector.