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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Nightside Magnetosphere-Ionosphere Current Circuit: Implications for Auroral Streamers and Pi2 Pulsations
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Nightside Magnetosphere-Ionosphere Current Circuit: Implications for Auroral Streamers and Pi2 Pulsations

机译：阴面Magnetosphere-Ionosphere当前电路:对极光的条幅和的影响Pi2 Pulsations

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We investigate the electrodynamic coupling of the nightside magnetosphere-ionosphere system using the analogy of a current circuit. In our model circuit the generator drives a constant current, which flows through the magnetotail and ionosphere branches. The magnetotail branch has a capacitor C and resistor R_T, whereas the ionospheric branch has an inductor L and resistor R_I. Each element is physically described with local quantities and geometries. For R_T ? R_I the electric circuit is characterized by three time constants: τ_(CR)(=CR_T), τ_(LC)(=√LC), and τ_(L/R)(=L/R_I). It is found that τ_(CR) is of the order of the ion gyroperiod in the plasma sheet, and τ_(LC) and τ_(L/R) correspond to the eigenperiod and decay time of the field line oscillation, respectively. Therefore, despite the variability of each circuit element, τ_(CR) ? τ_(LC) ? τ_(L/R) holds generally. It is found that under this condition the current circuit is characterized as overdamped, and its decay time constant is given by τ_(L/R). R_I is smaller, and therefore, τ_(L/R) is longer as the structure is more elongated in the direction of convection. This may explain why the auroral streamers, which are considered to be the ionospheric manifestation of fast flows in the plasma sheet, last significantly longer than the flows themselves. Another application is the Pi2 pulsations at the substorm onsets. If R_T increases by a factor of τ_(LC)/τ_(CR), the system indeed becomes underdamped, and the oscillation period is given by 2πτ_(LC). It is suggested that the substorm initiation is a distinct process with a significant enhancement of tail resistivity in a localized area.
机译：我们调查的电动耦合阴面magnetosphere-ionosphere系统使用当前的类比电路。发电机驱动恒流电路,流经磁尾和电离层分支。电容器C和电阻器R_T,而电离层分支有电感L和电阻R_I。当地的数量和几何图形。电路的特点是三个时间常数τ_ (CR) (= CR_T),τ_ (LC)(=√LC)τ_ (L / R) (= L / R_I)。等离子体中的离子gyroperiod的顺序表,τ_ (LC)和τ_ (L / R)对应线的固有周期和衰减时间字段分别振荡。每个电路元件的可变性,τ_ (CR) ?τ_ (LC) ?在这种情况下,目前的电路过阻尼的特点,其衰减时间常数是由τ_ (L / R)。因此,τ_ (L / R)长结构在对流的方向更细长。这或许可以解释为什么极光带,被认为是电离层表现的快速流动等离子体,去年显著长于流动他们自己。在亚暴发作脉动。增加系数τ_ (LC) /τ_ (CR)系统确实变得欠阻尼的,振荡周期是2πτ_ (LC)。建议亚暴启动是一个不同的过程有显著的增强的尾巴在局部区域电阻率。

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