Geospace Concussion: Global Reversal of Ionospheric Vertical Plasma Drift in Response to a Sudden Commencement

• Published in: Geophysical research letters Vol. 49; no. 19; pp. e2022GL100014 - n/a
• Main Authors: Shi, Xueling, Lin, Dong, Wang, Wenbin, Baker, Joseph B. H., Weygand, James M., Hartinger, Michael D., Merkin, Viacheslav G., Ruohoniemi, J. Michael, Pham, Kevin, Wu, Haonan, Angelopoulos, Vassilis, McWilliams, Kathryn A., Nishitani, Nozomu, Shepherd, Simon G.
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 16.10.2022; John Wiley and Sons Inc
• Subjects: Charged particles; Compression; Concussion; Current Systems; Drift; Earth magnetosphere; Electric currents; Electric field; Electric Fields; Field‐aligned Currents and Current Systems; Geomagnetic field; geomagnetic storm; Ionosphere; Ionosphere/Magnetosphere Interactions; Ionospheric Dynamics; Ionospheric electric fields; ionospheric vertical drift; Magnetic field; Magnetic fields; Magnetism; Magnetosphere/Ionosphere Interactions; Magnetospheric Physics; Magnetospheric waves; Movement; Numerical Modeling; Plasma drift; Radar; Radar data; Radar networks; Research Letter; Resolution; Shock; Shock waves; Space Sciences; sudden commencement; SuperDARN; Temporal resolution; Thermosphere; Vertical drift; Vertical motion; ionospheric vertical drift; geomagnetic storm; SuperDARN; sudden commencement
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2022GL100014

An interplanetary shock can abruptly compress the magnetosphere, excite magnetospheric waves and field‐aligned currents, and cause a ground magnetic response known as a sudden commencement (SC). However, the transient (<∼1 min) response of the ionosphere‐thermosphere system during an SC has been little studied due to limited temporal resolution in previous investigations. Here, we report observations of a global reversal of ionospheric vertical plasma motion during an SC on 24 October 2011 using ∼6 s resolution Super Dual Auroral Radar Network ground scatter data. The dayside ionosphere suddenly moved downward during the magnetospheric compression due to the SC, lasting for only ∼1 min before moving upward. By contrast, the post‐midnight ionosphere briefly moved upward then moved downward during the SC. Simulations with a coupled geospace model suggest that the reversed E⃗×B⃗ $\vec{E}\times \vec{B}$ vertical drift is caused by a global reversal of ionospheric zonal electric field induced by magnetospheric compression during the SC. Plain Language Summary It is well‐known that a shock wave can suddenly compress objects they directly interact with. In this study, we report a special case in the geospace environment in which an interplanetary shock produced a concussion‐like response in the ionosphere that was tens of thousands of kilometers away from the location where the shock first impacted. The ionized part of the atmosphere, or the ionosphere, was remotely connected to the magnetosphere‐the region of geospace dominated by the Earth's magnetic field‐via electric currents. When the magnetosphere was abruptly compressed after the shock arrival, a pair of electric currents flowing along the geomagnetic field lines was generated in the dayside mid‐latitudes. The newly generated currents flipped the dayside ionospheric electric field from eastward to westward, leading to a downward motion of dayside ionospheric charged particles. Within 1 minute, the vertical motion and zonal electric field flipped again to the direction before the compression due to the generation of another pair of electric currents with an opposite sense to the first pair. This study depicts a global picture of the transient ionospheric response using multi‐point high‐resolution measurements and simulations with a state‐of‐the‐art fully coupled geospace model. Key Points Dayside ionospheric plasma undergoes a transient motion from downward to upward during a sudden commencement (SC) Both observations and simulations show that the reversed vertical drift is a global response of the ionosphere to the SC The transient response is caused by a reversal of induced zonal electric field during the SC