Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique, Observatoire de Paris, Université Paris Sciences et Lettres, Centre National de la Recherche Scientifique, Sorbonne Université, Université Paris Diderot, Sorbonne Paris Cité, 5 Place Jules Janssen, 92195 Meudon, France.
Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, USA.
Science. 2018 Oct 5;362(6410). doi: 10.1126/science.aat2027.
Understanding how auroral radio emissions are produced by magnetized bodies requires in situ measurements within their source region. Saturn's kilometric radiation (SKR) has been widely used as a remote proxy of Saturn's magnetosphere. We present wave and plasma measurements from the Cassini spacecraft during its ring-grazing high-inclination orbits, which passed three times through the high-altitude SKR emission region. Northern dawn-side, narrow-banded radio sources were encountered at frequencies of 10 to 20 kilohertz, within regions of upward currents mapping to the ultraviolet auroral oval. The kilometric waves were produced on the extraordinary mode by the cyclotron maser instability from 6- to 12-kilo-electron volt electron beams and radiated quasi-perpendicularly to the auroral magnetic field lines. The SKR low-frequency sources appear to be strongly controlled by time-variable magnetospheric electron densities.
理解磁化体产生极光无线电辐射的机制需要在其源区进行原位测量。土星的千赫兹辐射（SKR）已被广泛用作土星磁层的远程代理。我们展示了卡西尼号飞船在其掠过土星环的高倾斜轨道期间的波动和等离子体测量数据，该飞船三次穿过高空 SKR 发射区域。在朝向极昼侧、频率为 10 至 20 千赫兹的狭窄无线电波源，与映射到紫外线极光椭圆的向上电流区域内被探测到。千赫兹波由回旋脉泽不稳定性在 6 至 12 千电子伏特电子束中以超常模式产生，并准垂直于极光磁场线辐射。SKR 低频源似乎受到时变磁层电子密度的强烈控制。
