Feedback Interactions Between the Ionosphere and Magnetosphere at Middle Latitude
Feedback Interactions Between the Ionosphere and Magnetosphere at Middle Latitude
复制标题
DOI：
10.1029/2021ja029990
复制
发表时间：
2022-02
期刊：
影响因子：
--
通讯作者：
M. Alimaganbetov;Embry-Riddle Aeronautical
中科院分区：
文献类型：
--
作者：
M. Alimaganbetov;Embry-Riddle Aeronautical
观测表明，在地面、内磁层和太阳风的不同纬度上，经常同时探测到频率在1兆赫左右的磁脉动。一些研究表明，太阳风携带的动态压力或磁场振荡与高纬度地面上检测到的超低频（ULF）波之间存在耦合。我们提出了亚暴期间中纬度地面磁力仪检测到的超低频波的数值研究结果。我们研究了这些波是由电离层中大尺度电场驱动的电离层反馈不稳定性产生的假设。这个领域是与表面波传播沿着环境磁场上的等离子体密度发生在赤道磁层的一个强垂直梯度。等离子体密度的梯度与等离子体层顶有关。亚暴期间等离子体层顶发生侵蚀时，等离子体层顶向中纬度移动。来自外部驱动器的能量可以耦合到大尺度表面阿尔文波，阿尔文波沿着沿着场线传播到电离层，并在中纬度地区产生小尺度强ULF波和场向电流。双流体磁流体动力学模型的模拟证实了这种情况，数值结果显示出与观测良好的定量一致性。
Observations show that magnetic pulsations with frequencies around 1 mHz are frequently detected simultaneously at different latitudes on the ground, in the inner magnetosphere, and in the solar wind. The coupling between oscillations in the dynamic pressure or magnetic field carried by the solar wind and the ultra‐low frequency (ULF) waves detected on the ground at high latitudes has been suggested in several studies. We present results from a numerical study of ultra‐low‐frequency waves detected by the ground magnetometers at middle latitudes during substorm. We investigate the hypothesis that these waves are generated by the ionospheric feedback instability driven by the large‐scale electric field in the ionosphere. This field is associated with the surface waves propagating along the ambient magnetic field on a strong perpendicular gradient in the plasma density occurring in the equatorial magnetosphere. The gradient in the plasma density is associated with the plasmapause. The plasmapause moves to the middle latitude when the plasmasphere erodes during substorm. The energy from the external driver can be coupled to the large‐scale surface Alfvén waves traveling along the field lines into the ionosphere and generating small‐scale intense ULF waves and field‐aligned currents at middle latitudes. The simulations of the two‐fluid magnetohydrodynamics model confirm this scenario, and the numerical results show a good quantitative agreement with the observations.