Anti-planetward auroral electron beams at Saturn
Anti-planetward auroral electron beams at Saturn
复制标题
土星上的反行星极光电子束
DOI：
10.1038/nature04401
复制
发表时间：
2006
期刊：
影响因子：
64.8
通讯作者：
M. Dougherty
中科院分区：
文献类型：
--
作者：
J. Saur;B. Mauk;D. Mitchell;N. Krupp;K. Khurana;S. Livi;S. Krimigis;P. Newell;D. Williams;P. Brandt;A. Lagg;E. Roussos;M. Dougherty
地球上强烈的离散极光是由电子激发的，电子沿着磁力线向行星加速。令人惊讶的是，最近观察到了以相反方向加速的电子。这种反地球加速的机制和意义是高度不确定的，因为传统上只考虑地球加速，观察结果仍然有限。目前也不清楚电子的向上加速是极光过程的必要部分，还是仅仅是地球复杂空间环境的一个特殊特征。在这里，我们报道了土星磁层中的电子束沿着统计上映射到极光区域的场线向行星方向的加速。这些波束的能谱在性质上与在地球上观测到的类似，而观测到的波束中的能量通量与激发土星极光所需的能量相当。这些光束，连同在地球上的观测和木星磁层中鲜为人知的电子束，证明了反行星加速是极光的普遍特征。光束中包含的能量表明，向上加速是整个极光过程的重要组成部分。
Strong discrete aurorae on Earth are excited by electrons, which are accelerated along magnetic field lines towards the planet. Surprisingly, electrons accelerated in the opposite direction have been recently observed. The mechanisms and significance of this anti-earthward acceleration are highly uncertain because only earthward acceleration was traditionally considered, and observations remain limited. It is also unclear whether upward acceleration of the electrons is a necessary part of the auroral process or simply a special feature of Earth's complex space environment. Here we report anti-planetward acceleration of electron beams in Saturn's magnetosphere along field lines that statistically map into regions of aurora. The energy spectrum of these beams is qualitatively similar to the ones observed at Earth, and the energy fluxes in the observed beams are comparable with the energies required to excite Saturn's aurora. These beams, along with the observations at Earth and the barely understood electron beams in Jupiter's magnetosphere, demonstrate that anti-planetward acceleration is a universal feature of aurorae. The energy contained in the beams shows that upward acceleration is an essential part of the overall auroral process.