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Investigating the Development of Distinctive Subauroral Flow Channels During the November 7–8, 2004 Superstorm

We investigate the development of large (∼3,000 m/s) subauroral flows occurring during the November 7–8, 2004 Superstorm by utilizing multisatellite and multiinstrument measurements from the Magnetosphere (M), topside Ionosphere (I), and Thermosphere (T). We present eight scenarios (Sc‐1–Sc‐8) depicting the development of large SubAuroral Polarization Streams (SAPS) in the initial phase (Sc‐1–Sc‐3) and recovery phase (Sc‐5), and structured SAPS (Sc‐4, Sc‐6–Sc‐7) and Double‐peak SubAuroral Ion Drifts (DSAID) in the recovery phase (Sc‐8). Magnetospheric observations reveal dayside magnetopause reconnection increasing both the magnetospheric convection electric field and the large‐scale Field‐Aligned Currents (FACs), long‐lasting (∼5 h) secondary dipolarizations during the initial phase, and a series of dipolarization events during the recovery phase. Ionospheric observations reveal the development of these large subauroral flows (i) during forward and reverse plasma convections—when the topside ionosphere received earthward energy from the magnetosphere and when the diversion of cross‐tail currents in the stretched magnetotail activated the Substorm Current Wedge (SCW)—and (ii) in a short‐circuited system that acted as a voltage generator. Thermospheric observations reveal earthward energy deposition from the ionosphere that drove wind surges—implying the presence of Atmospheric Gravity Waves (AGWs) and Traveling Ionospheric Disturbances (TIDs)—propagating equatorward/poleward and passing through the trough region, and further enhancing the subauroral flows by deepening the trough. From these results we conclude that the strong M‐I‐T coupling occurring under superstorm conditions played a significant role in the enhancement of the subauroral flows investigated.