Ruhunusiri S, Howes G G, Halekas J S
Department of Physics and Astronomy, The University of Iowa, Iowa City, IA, USA.
J Geophys Res Space Phys. 2020 Sep;125(9). doi: 10.1029/2020ja028100. Epub 2020 Aug 21.
We perform a power spectral analysis of magnetic field fluctuations measured by the Rosetta spacecraft's magnetometer at comet 67P/Churyumov-Gerasimenko. We interpret the power spectral signatures in terms of plasma turbulent processes and discover that different turbulent processes are prominent during different active phases of the comet. During the weakly active phase of the comet, dominant injection is prominent at low frequencies near 10 Hz, while partial energy cascade or dispersion is prominent at high frequencies near 10 Hz. During the intermediately active phase, uniform injection is prominent at low frequencies, while partial energy cascade or dispersion is prominent at high frequencies. During the strongly active phase of the comet, we find that partial energy cascade or dissipation is dominant at low frequencies, while partial energy cascade, dissipation, or dispersion is dominant at high frequencies. We infer that the temporal variations of the turbulent processes occur due to the evolution of the plasma environment of the comet as it orbits the Sun.
我们对罗塞塔号航天器的磁力计在67P/丘留莫夫－格拉西缅科彗星上测量到的磁场波动进行了功率谱分析。我们根据等离子体湍流过程来解释功率谱特征，并发现不同的湍流过程在彗星的不同活跃阶段占主导地位。在彗星的弱活跃阶段，主导注入在接近10赫兹的低频处较为突出，而部分能量级联或频散在接近10赫兹的高频处较为突出。在中等活跃阶段，均匀注入在低频处较为突出，而部分能量级联或频散在高频处较为突出。在彗星的强活跃阶段，我们发现部分能量级联或耗散在低频处占主导地位，而部分能量级联、耗散或频散在高频处占主导地位。我们推断，湍流过程的时间变化是由于彗星绕太阳公转时其等离子体环境的演化所致。
