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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Impedance characteristics of an active antenna at whistler mode frequencies
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Impedance characteristics of an active antenna at whistler mode frequencies

机译：有源天线的阻抗特征惠斯勒模式频率

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摘要

We use the radio plasma imager (RPI) on the IMAGE satellite to investigate the impedance characteristics of an active electric antenna in space plasma at whistler mode frequencies. A dedicated experiment was carried out on 21-22 September 2005 for two orbits in the plasmasphere. The input impedance characteristics of the dipole antenna submerged in plasma is determined at whistler frequencies. The results are consistent with a physical model in which the antenna is negatively charged to a large voltage and the plasma around each antenna element forms an ion sheath that varies with time in its radius. Within the plasmasphere, these sheaths are a part of the antenna-plasma system and represent a capacitive component of the tuned antenna circuit. It is shown that, inside the plasmasphere, the RPI antenna capacitance varied from 430 to 480 pF. The plasma sheath formed around the antenna in the plasmasphere increases its capacitance by 20-30 with respect to the near-free space capacitance (364 pF). Comparison of these values to model calculations shows good agreement with a difference smaller than 5. Measurements of the antenna input resistance showed that, inside the plasmasphere, its value was between 200 and 500 Ω, varying considerably with changes in the ambient electron density and cyclotron frequency. The measured antenna input resistance is compared to model calculations.
机译：我们用收音机等离子成像仪(RPI)的形象卫星调查阻抗一个活跃的电动天线的特性空间等离子体在惠斯勒模式频率。专门的实验进行了21 - 222005年9月两个轨道等离子体层。偶极子天线的淹没在等离子体在惠斯勒频率决定。和的物理模型是一致的吗天线是带负电荷的很大的电压和每个天线元素周围的等离子体形式离子鞘,随时间的半径。是一个antenna-plasma系统的一部分代表一个电容组件的调优天线电路。等离子体层,零售物价指数天线电容变化从430年到480年pF,形成的等离子体鞘在天线的等离子体层增加其电容的20% - -30%近乎免费空间电容(364 pF)。这些值模型计算显示良好协议差异小于5%。天线输入电阻的测量显示,等离子体层内,它的价值在200年和500年之间Ω,明显不同与周围的电子密度的变化回旋频率。电阻相比,模型计算。

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