Limb polarization of Uranus and Neptune - I. Imaging polarimetry and comparison with analytic models
Limb polarization of Uranus and Neptune - I. Imaging polarimetry and comparison with analytic models
复制标题
天王星和海王星的肢体偏振 - I. 成像偏振测量及其与解析模型的比较
DOI：
10.1051/0004-6361:20053273
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发表时间：
2006
影响因子：
6.5
通讯作者：
D. Tschan
中科院分区：
文献类型：
--
作者：
H. Schmid;F. Joos;D. Tschan
本文介绍了天王星和海王星在R、i、a ndz波段的成像偏振测量。在所有的观察径向肢体极化的顺序为1%，检测到的位置角垂直于肢体。在两颗行星上，波长越短，偏振度越高。作为第一近似，极化似乎沿整个翼沿着同样强。这与木星和土星不同，在木星和土星上，只有在两极才能观察到显著的临边偏振。我们确定的肢体偏振和径向肢体偏振配置文件的通量加权平均值，并研究了由于我们的观测的有限空间分辨率的偏振信号的退化和抵消效应。考虑到这一点，我们推导出在天王星和海王星的肢体极化校正值。结果进行了比较，与瑞利散射大气的半无限情况下，有限层与地面反射的分析模型。比较表明，检测到的偏振与预期是兼容的。这表明，临边偏振测量提供了一个强大的诊断工具，调查散射粒子在天王星和海王星的上层大气的属性，特别是如果更复杂的数值模拟的临边偏振变得可用。从总体的临边极化强度可以看出，天王星和海王星在大相位角时的盘积分极化强度较高（p > 20%）。这对于未来对具有类似天王星和海王星的大气特性的太阳系外行星的偏振探测是有意义的。
Imaging polarimetry of Uranus and Neptune in the R, i ,a ndz bands are presented. In all observations a radial limb polarization on the order of 1% was detected with a position angle perpendicular to the limb. The polarization is higher in both planets for the shorter wavelength bands. As a first approximation, the polarization seems to be equally strong along the entire limb. This is unlike Jupiter and Saturn, where significant limb polarization is only observed at the poles. We determined flux-weighted averages of the limb polarization and radial limb polarization profiles, and investigated the degradation and cancellation effects in the polarization signal due to the seeing-limited spatial resolution of our observations. Taking this into account we derived corrected values for the limb polarization in Uranus and Neptune. The results are compared with analytic models for Rayleigh scattering atmospheres for the semi-infinite case and finite layers with ground albedo. The comparison shows that the detected polarization is compatible with expectations. This indicates that limb-polarization measurements offer a powerful diagnostic tool for investigating the properties of scattering particles in the upper atmospheres of Uranus and Neptune, in particular if more sophisticated numerical modeling of the limb polarization becomes available. It is also concluded from the overall strength of the limb polarization that the disk-integrated polarization of Uranus and Neptune for large phase angles is high (p > 20%). This is of interest for future polarimetric detections of extra-solar planets with atmospheric properties similar to Uranus and Neptune.