Frequency drift of Saturn chorus emission compared to nonlinear theory
Frequency drift of Saturn chorus emission compared to nonlinear theory
复制标题
DOI：
10.1002/jgra.50165
复制
发表时间：
2013-03
期刊：
影响因子：
--
通讯作者：
J. Menietti;Y. Katoh;G. Hospodarsky;D. Gurnett
中科院分区：
文献类型：
--
作者：
J. Menietti;Y. Katoh;G. Hospodarsky;D. Gurnett
卡西尼射电和等离子体波研究在土星观测到非线性漂移频率合唱的精细结构。在一个高倾角的轨道上，卡西尼号在磁赤道10°以内的接近恒定的L壳层，观察到适度强烈的非线性合唱。卡西尼号在磁赤道两侧观测到一个强烈的合唱和大带宽的区域，在磁赤道附近观测到较低的强度和带宽。利用观测到的等离子体波谱和电子相空间分布，我们测量了合唱产生区域内或附近的等离子体参数，并根据Omura等人的非线性波增长理论和Trakhtengerts的后向波振子理论，估算了频率扫描速率的理论值。这两种理论产生的速率都在观测值的2倍以内，但非线性波增长理论的值更接近于所研究情况下的观测值。提出的工作是一致的非线性理论的代合唱，但也揭示了一个明显的区域较弱或线性合唱增长最接近的磁赤道在土星。
The fine structure of nonlinear drifting‐frequency chorus is observed at Saturn by the Cassini Radio and Plasma Wave Investigation. During a high‐inclination orbit in which Cassini is at near‐constant L‐shell within about 10° of the magnetic equator, moderately intense nonlinear chorus is observed. Cassini observed a region of intense chorus and large bandwidth a few degrees on either side of the magnetic equator, with lower intensities and bandwidths observed nearest the magnetic equator. Using the observed plasma wave spectra and electron phase space distribution, we have measured plasma parameters within or near the chorus generation region and evaluated the theoretical value of the frequency sweep rate, ∂f/∂t, based on the nonlinear wave growth theory of Omura et al. and the backward wave oscillator theory of Trakhtengerts. Both theories produce rates that are within a factor of 2 of the observed values, but the nonlinear wave growth theory values are closer to the observations for the cases examined. The work presented is consistent with nonlinear theory in the generation of chorus, but also reveals a distinct region of weaker or linear chorus growth nearest to the magnetic equator at Saturn.