Abstract. During the main phase of geomagnetic storms large positive ionospheric plasma density anomalies arise at middle and polar latitudes. A prominent example is the tongue of ionisation (TOI), which extends poleward from the dayside storm-enhanced density (SED) anomaly, often crossing the polar cap and streaming with the plasma convection flow into the nightside ionosphere. A fragmentation of the TOI anomaly contributes to the formation of polar plasma patches partially responsible for the scintillations of satellite positioning signals at high latitudes. To investigate this intense plasma anomaly, numerical simulations of plasma and neutral dynamics during the geomagnetic superstorm of 20 November 2003 are performed using the Thermosphere Ionosphere Electrodynamics Global Circulation Model (TIE-GCM) coupled with the statistical parameterisation of high-latitude plasma convection. The simulation results reproduce the TOI features consistently with observations of total electron content and with the results of ionospheric tomography, published previously by the authors. It is demonstrated that the fast plasma uplift, due to the electric plasma convection expanded to subauroral mid-latitudes, serves as a primary feeding mechanism for the TOI anomaly, while a complex interplay between electrodynamic and neutral wind transports is shown to contribute to the formation of mid-latitude SED anomaly. It is suggested that better representation of the high-latitude plasma convection is needed. The results are discussed in the context of space weather modelling.

中文翻译：

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地磁超级暴风雨中的电离极舌

摘要。在地磁风暴的主要阶段，在中纬度和纬度会出现较大的正电离层等离子体密度异常。一个突出的例子是电离舌（TOI），它从白天的风暴增强密度（SED）异常向极地延伸，经常越过极帽，并随等离子体对流流向夜间的电离层。TOI异常的碎片导致极性等离子体斑块的形成，部分导致了高纬度卫星定位信号的闪烁。为了调查这种严重的血浆异常，利用热球电离层电动力学全球环流模型（TIE-GCM）结合高纬度等离子对流的统计参数化，对2003年11月20日地磁超级风暴期间的等离子体和中性动力学进行了数值模拟。仿真结果重现了TOI的特征，与总电子含量的观察结果以及电离层层析成像的结果（作者先前发表的结果）一致。结果表明，由于电浆对流扩展到了极光下中纬度，快速的等离子体隆起是TOI异常的主要进给机制，而电动力和中性风之间的复杂相互作用被证明有助于形成中纬度SED异常。建议需要更好地表示高纬度等离子体对流。在空间天气建模的背景下讨论了结果。