Io‐related Jovian auroral arcs: Modeling parallel electric fields
Io‐related Jovian auroral arcs: Modeling parallel electric fields
复制标题
与木卫一相关的木星极光弧：平行电场建模
DOI：
10.1029/2002ja009247
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发表时间：
2003
影响因子：
--
通讯作者：
P. Delamere
中科院分区：
文献类型：
--
作者：
Y. Su;R. Ergun;F. Bagenal;P. Delamere
[1] 最近对木星极光弧的观测表明，电子正在木卫一磁足迹下游加速，产生可检测到的发射。在准中性和施加电势降的约束下，使用一维空间、二维速度静态 Vlasov 解研究下游电子加速。该代码确定了木卫一尾流向上（相对于木星）电流区域中沿磁场通量管的自洽带电粒子分布和电势结构。通量管的边界一端是木卫一环面，另一端是木星的电离层。结果表明，局部电势下降倾向于在 1.5-2.5 Rj Jovicentric 距离处形成。足够高的二次电子密度会导致产生类似于地球上的极光腔。有趣的是，模型结果表明，木卫一环面中的质子和热电子群控制着木卫一环面和木星之间的电子电流密度，因此可能控制木卫一磁足迹下游极光的能量通量和亮度。平行电场预计还会在极光腔内产生不稳定的马蹄形电子分布，这可能导致壳层电子回旋脉泽不稳定。我们模型的结果表明，尽管木星的边界条件不同且离心势较大，但极光腔的形成可能与地球相似，并且平行电场可能是木卫一控制的十米无线电发射的源机制。
[1] Recent observations of auroral arcs on Jupiter suggest that electrons are being accelerated downstream from Io's magnetic footprint, creating detectable emissions. The downstream electron acceleration is investigated using one-dimensional spatial, two-dimensional velocity static Vlasov solutions under the constraint of quasi-neutrality and an applied potential drop. The code determines self-consistent charged particle distributions and potential structure along a magnetic field flux tube in the upward (with respect to Jupiter) current region of Io's wake. The boundaries of the flux tube are the Io torus on one end and Jupiter's ionosphere on the other. The results indicate that localized electric potential drops tend to form at 1.5-2.5 Rj Jovicentric distance. A sufficiently high secondary electron density causes an auroral cavity to be produced similar to that on Earth. Interestingly, the model results suggest that the proton and the hot electron population in the Io torus control the electron current densities between the Io torus and Jupiter and thus may control the energy flux and the brightness of the aurora downstream from Io's magnetic footprint. The parallel electric fields also are expected to create an unstable horseshoe electron distribution inside the auroral cavity, which may lead to the shell electron cyclotron maser instability. Results from our model suggest that in spite of the differing boundary conditions and the large centrifugal potentials at Jupiter, the auroral cavity formation may be similar to that of the Earth and that parallel electric fields may be the source mechanism of Io-controlled decametric radio emissions.