Magnetospherically driven optical and radio aurorae at the end of the stellar main sequence
Magnetospherically driven optical and radio aurorae at the end of the stellar main sequence
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DOI：
10.1038/nature14619
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发表时间：
2015-07
期刊：
影响因子：
64.8
通讯作者：
G. Hallinan;S. P. Littlefair;G. Cotter;S. Bourke;L. K. Harding;J. Pineda;R. P. Butler;A. Golden;G. Basri;J. Doyle;M. Kao;S. Berdyugina;A. Kuznetsov;M. Rupen;A. Antonova
中科院分区：
文献类型：
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作者：
G. Hallinan;S. P. Littlefair;G. Cotter;S. Bourke;L. K. Harding;J. Pineda;R. P. Butler;A. Golden;G. Basri;J. Doyle;M. Kao;S. Berdyugina;A. Kuznetsov;M. Rupen;A. Antonova
极光可以从太阳系中所有的磁化行星上探测到，包括地球。它们由磁层电流系统提供动力，导致高能电子沉淀到高层大气的高纬度地区。在气体巨行星的情况下，这些极光包括由沉淀电子产生的千赫兹和兆赫频率的高度极化无线电发射，以及光谱中红外线、光学、紫外线和X射线部分的连续和线发射，这些发射与氢为主的大气的碰撞激发和加热有关。在这里，我们报告同步无线电和光学光谱观测的对象在恒星主序的末端，位于恒星和褐矮星之间的边界，从那里我们已经检测到无线电和光学极光发射都由磁层电流供电。像我们的太阳这样的恒星的磁场活动是由它们的低层大气中发生的过程提供动力的，而这些极光则是由矮星星的磁层中更远的过程提供动力的，这些过程将能量耦合到低层大气中。耗散的能量至少比木星磁层中产生的能量大四个数量级，这表明极光可能是大规模磁层的普遍存在的特征，可以扩展到远大于我们太阳系中观测到的亮度。这些磁层电流系统也可能在为褐矮星上报告的一些天气现象提供动力方面发挥作用。
Aurorae are detected from all the magnetized planets in our Solar System, including Earth. They are powered by magnetospheric current systems that lead to the precipitation of energetic electrons into the high-latitude regions of the upper atmosphere. In the case of the gas-giant planets, these aurorae include highly polarized radio emission at kilohertz and megahertz frequencies produced by the precipitating electrons, as well as continuum and line emission in the infrared, optical, ultraviolet and X-ray parts of the spectrum, associated with the collisional excitation and heating of the hydrogen-dominated atmosphere. Here we report simultaneous radio and optical spectroscopic observations of an object at the end of the stellar main sequence, located right at the boundary between stars and brown dwarfs, from which we have detected radio and optical auroral emissions both powered by magnetospheric currents. Whereas the magnetic activity of stars like our Sun is powered by processes that occur in their lower atmospheres, these aurorae are powered by processes originating much further out in the magnetosphere of the dwarf star that couple energy into the lower atmosphere. The dissipated power is at least four orders of magnitude larger than what is produced in the Jovian magnetosphere, revealing aurorae to be a potentially ubiquitous signature of large-scale magnetospheres that can scale to luminosities far greater than those observed in our Solar System. These magnetospheric current systems may also play a part in powering some of the weather phenomena reported on brown dwarfs.