title: Direct observations of the evolution of polar cap ionization patches.
abstract: Patches of ionization are common in the polar ionosphere, where their motion and associated density gradients give variable disturbances to high-frequency (HF) radio communications, over-the-horizon radar location errors, and disruption and errors to satellite navigation and communication. Their formation and evolution are poorly understood, particularly under disturbed space weather conditions. We report direct observations of the full evolution of patches during a geomagnetic storm, including formation, polar cap entry, transpolar evolution, polar cap exit, and sunward return flow. Our observations show that modulation of nightside reconnection in the substorm cycle of the magnetosphere helps form the gaps between patches where steady convection would give a "tongue" of ionization (TOI).
authors.affiliation: State Oceanic Administration People's Republic of China Key Laboratory for Polar Science, Polar Research Institute of China, Shanghai, China. zhangqinghe@pric.gov.cn
authors.forename: Qing-He
authors.initials: QH
authors.lastname: Zhang
authors.forename: Bei-Chen
authors.initials: BC
authors.lastname: Zhang
authors.forename: Michael
authors.initials: M
authors.lastname: Lockwood
authors.forename: Hong-Qiao
authors.initials: HQ
authors.lastname: Hu
authors.forename: Jøran
authors.initials: J
authors.lastname: Moen
authors.forename: J Michael
authors.initials: JM
authors.lastname: Ruohoniemi
authors.forename: Evan G
authors.initials: EG
authors.lastname: Thomas
authors.forename: Shun-Rong
authors.initials: SR
authors.lastname: Zhang
authors.forename: Hui-Gen
authors.initials: HG
authors.lastname: Yang
authors.forename: Rui-Yuan
authors.initials: RY
authors.lastname: Liu
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: McWilliams
authors.forename: Joseph B H
authors.initials: JB
authors.lastname: Baker