Transmission Line Model for Driving Plasma Convection in the Inner Magnetosphere
Transmission Line Model for Driving Plasma Convection in the Inner Magnetosphere
复制标题
用于驱动内磁层等离子体对流的传输线模型
DOI：
10.1029/155gm20
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
T. Kikuchi
中科院分区：
文献类型：
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作者：
T. Kikuchi
在极帽电位增长后，内磁层中的等离子体对流反应迅速，正如Hashimoto等人[2002]所证明的部分环电流的快速发展所揭示的那样。为了解释内磁层的快速响应，我们采用了Kikuchi和Araki [979b]开发的地球电离层波导（传输线）模型。本文研究了随场向电流传输的电势如何在波导中激发TMO模式，并证明了电势在地球电离层波导中以光速水平传输。然后，我们通过计算从地球电离层波导向上传输到导电电离层的坡印亭通量来评估TMO模式的衰减。当磁层的阿尔芬电导与电离层电导相比不是很小时，坡印亭通量的一部分进一步被输送到磁层。坡印亭通量的向上输运会造成水平传输能量的损失，从而导致TMO模式的衰减，但由于极电场的大小有限，与几何衰减相比，这种衰减并不大。我们强调与电离层电流相关的电场通过Alfven模式向上映射到磁层，这驱动了内磁层的等离子体对流。我们注意到电离层不是一个发电机，而是构成一条传输线，将电磁能量传输到内部磁层。
The plasma convection in the inner magnetosphere reacts quickly after a growth of the polar cap potential, as revealed by the quick onset of the development of the partial ring current as demonstrated by Hashimoto et al. [2002]. In order to explain the quick response of the inner magnetosphere, we apply the Earth-ionosphere waveguide (transmission line) model developed by Kikuchi and Araki [ 979b]. In this paper, we examine how the TMO mode is excited in the waveguide by the electric potential transported along with the field-aligned currents, and show that the electric potential is transmitted horizontally at the speed of light in the Earth-ionosphere waveguide. We then evaluate the attenuation of the TMO mode by calculating the Poynting flux transported upward from the Earth-ionosphere waveguide into the conducting ionosphere. A fraction of the Poynting flux is further transported into the magnetosphere when the Alfven conductance of the magnetosphere is not very small compared with the ionospheric conductance. The upward transportation of the Poynting flux causes a loss of the horizontally transmitting energy, resulting in the attenuation of the TMO mode, but it is not substantial compared to the geometrical attenuation due to the finite size of the polar electric field. We stress that the electric field associated with the ionospheric current is mapped upward into the magnetosphere by the Alfven mode, which drives the plasma convection in the inner magnetosphere. We note that the ionosphere is not a generator but constitutes a transmission line for the electromagnetic energy to be transported into the inner magnetosphere.