Electron acceleration at Jupiter: input from cyclotron-resonant interaction with whistler-mode chorus waves
Electron acceleration at Jupiter: input from cyclotron-resonant interaction with whistler-mode chorus waves
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DOI：
10.5194/angeo-31-1619-2013
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发表时间：
2013-10
影响因子：
1.9
通讯作者：
E. Woodfield;R. Horne;S. Glauert;J. Menietti;Y. Shprits
中科院分区：
文献类型：
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作者：
E. Woodfield;R. Horne;S. Glauert;J. Menietti;Y. Shprits
木星的辐射带是所有外行星中最强的。目前还不知道电子如何被加速到10兆电子伏或更高的能量。有人提出，回旋加速器-共振波-粒子之间的协同波相互作用可以在木卫一轨道附近将电子加速到几MeV。在这里，我们使用伽利略航天器观测到的合唱波强度来计算由于俯仰角和能量扩散而导致的电子通量的变化。我们表明，当考虑到波的带宽及其随L的变化时，俯仰角和由合唱波引起的能量扩散在L-壳处比先前显示的大8倍，大于10倍。我们利用伽利略数据的纬向波强度剖面图，利用英国南极调查辐射带（BAS）模式模拟了电子通量的时间演变。这个剖面将强烈的合唱波限制在磁力线附近，其峰值强度在纬度5处。在BAS模型中，当能量在3mev左右时，电子通量增加了一个数量级。将我们的结果推广到L = 14，表明回旋共振与合唱波的相互作用对于L = 10以上的电子加速同样重要。这些结果表明，木星上的回旋共振相互作用产生了显著的电子加速，有助于木星辐射带的形成，也增加了l -壳层的范围，这种机制应该被考虑。
Jupiter has the most intense radiation belts of all the outer planets. It is not yet known how electrons can be accelerated to energies of 10 MeV or more. It has been sug- gested that cyclotron-resonant wave-particle interactions by chorus waves could accelerate electrons to a few MeV near the orbit of Io. Here we use the chorus wave intensities ob- served by the Galileo spacecraft to calculate the changes in electron flux as a result of pitch angle and energy diffusion. We show that, when the bandwidth of the waves and its vari- ation with L are taken into account, pitch angle and energy diffusion due to chorus waves is a factor of 8 larger at L- shells greater than 10 than previously shown. We have used the latitudinal wave intensity profile from Galileo data to model the time evolution of the electron flux using the British Antarctic Survey Radiation Belt (BAS) model. This pro- file confines intense chorus waves near the magnetic equa- tor with a peak intensity at 5 latitude. Electron fluxes in the BAS model increase by an order of magnitude for ener- gies around 3 MeV. Extending our results to L = 14 shows that cyclotron-resonant interactions with chorus waves are equally important for electron acceleration beyond L = 10. These results suggest that there is significant electron ac- celeration by cyclotron-resonant interactions at Jupiter con- tributing to the creation of Jupiter's radiation belts and also increasing the range of L-shells over which this mechanism should be considered.