Modeling Jovian hectometric attenuation lanes during the Cassini flyby of Jupiter
Modeling Jovian hectometric attenuation lanes during the Cassini flyby of Jupiter
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卡西尼号飞越木星期间对木星百米衰减线进行建模
DOI：
10.1002/2014ja020815
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
James R. Thieman
中科院分区：
文献类型：
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作者：
Masafumi Imai;Alain Lecacheux;Michel Moncuquet;Fran Bagenal;Charles A. Higgins;Kazumasa Imai;James R. Thieman
卡西尼号宇宙飞船在 2000 年底和 2001 年初遭遇木星，揭示了木星百米辐射 (HOM) 的持久特性，这些辐射源自极地地区的极光磁场线。 HOM 动态频谱的独特属性之一，称为衰减通道，表现为旋转调制、明确的强度降低区域，两侧是增强区域。这些通道似乎是无线电波在高密度介质中折射的结果——要么是由情况（i）与木卫一轨道相连的磁性L-壳层中密度增强造成的，要么是由木卫一等离子体环面本身的情况（ii）引起的，或者两者兼而有之。在本文中，我们研究了在磁 L 值等于 30 时产生的连续射电经度中具有不同锥体半角的 0.5-3.0 MHz 发射的 HOM 射线路径。我们使用双卡帕粒子分布来推导 Io 等离子体环中密度的扩散平衡分布。沿 Io 通量壳“带”区域增强的密度不规则性可以用最大密度 n0 和宽度（通量壳分布的半宽）σ 的高斯密度分布来描述。结果，我们发现情况（i）的解释可以通过所有圆锥半角出现的衰减带来解释，并且合理的通量壳密度n0是，在来自扩散平衡模型的特定纬度相关密度之上，估计为100 cm−3，半宽σ= 5.0 Io半径。
The Jupiter encounter by the Cassini spacecraft in late 2000 and early 2001 unveiled persistent properties of Jupiter's hectometric (HOM) radiation originating along auroral magnetic field lines in the polar regions. One of the unique properties of the HOM dynamic spectrum, known as attenuation lanes, appears as rotationally modulated, well‐defined regions of lowered intensity, flanked by regions of enhancement. These lanes seem to be the result of refraction of radio waves in a high‐density medium–either caused by Case (i) enhanced density in the magnetic L‐shell connected to Io's orbit or Case (ii) in the Io plasma torus itself or both. In this paper, we investigate the HOM ray paths of 0.5–3.0 MHz emissions with various cone half‐angles in the continuous radio longitudes generating at the magneticL‐value equal to 30. We use bi‐kappa particle distributions to derive diffusive equilibrium distributions of density in the Io plasma torus. The enhanced density irregularities along the Io flux shell “ribbon” region can be described with a Gaussian density distribution of a maximum densityn0and breadth (half‐width of the distribution across the flux shell)σ. As a result, we found that the interpretation of Case (i) can be accounted for by the attenuation lanes which appear for all cone half‐angles, and the reasonable flux shell densityn0is, on top of specific latitude‐dependent density from the diffusive equilibrium model, estimated as 100 cm−3with the half‐widthσ= 5.0 Io radii.