The origin of Jupiter's outer radiation belt
The origin of Jupiter's outer radiation belt
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DOI：
10.1002/2014ja019891
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发表时间：
2014-05-01
影响因子：
2.8
通讯作者：
Shprits, Y. Y.
中科院分区：
文献类型：
--
作者：
Woodfield, E. E.;Horne, R. B.;Shprits, Y. Y.
木星强烈的内部辐射带（在1.5 RJ时超过50 MeV）通常被认为是由远离行星的电子径向扩散造成的。然而，这需要一个能量超过1 MeV的源，在5.9 RJ的木卫一轨道之外，这从来没有得到令人满意的解释。在这里，我们测试的假设，这个源人口可以形成一个非常软的能谱，粒子注入过程和共振电子加速通过哨声模式合唱波。我们使用英国南极调查辐射带模型来计算6.5和15 RJ之间的电子通量的变化，这些是第一次在木星结合波粒子相互作用和径向扩散的模拟。100 keV和1 MeV的电子通量分别在1天和10天后非常接近伽利略中期辐射电子模型谱。通量增加的主要驱动力是由合唱波引起的回旋共振加速。在相空间密度的峰值形成，使得在L内部近似9的径向扩散向木星输送电子，但在L外部近似9的径向扩散远离行星。结果是不敏感的初始能谱的柔软度，但依赖于在最小能量边界的通量的值。我们的结论是，在木星的内部辐射带的源人口确实可以形成波粒相互作用。
The intense inner radiation belt at Jupiter (>50 MeV at 1.5 RJ) is generally accepted to be created by radial diffusion of electrons from further away from the planet. However, this requires a source with energies that exceed 1 MeV outside the orbit of the moon Io at 5.9 RJ, which has never been explained satisfactorily. Here we test the hypothesis that this source population could be formed from a very soft energy spectrum, by particle injection processes and resonant electron acceleration via whistler mode chorus waves. We use the British Antarctic Survey Radiation Belt Model to calculate the change in the electron flux between 6.5 and 15 RJ; these are the first simulations at Jupiter combining wave particle interactions and radial diffusion. The resulting electron flux at 100 keV and 1 MeV lies very close to the Galileo Interim Radiation Electron model spectrum after 1 and 10 days, respectively. The primary driver for the increase in the flux is cyclotron resonant acceleration by chorus waves. A peak in phase space density forms such that inside L approximate to 9 radial diffusion transports electrons toward Jupiter, but outside L approximate to 9 radial diffusion acts away from the planet. The results are insensitive to the softness of the initial energy spectrum but do depend on the value of the flux at the minimum energy boundary. We conclude by suggesting that the source population for the inner radiation belt at Jupiter could indeed be formed by wave-particle interactions.