Determining solar effects in Neptune's atmosphere.
Determining solar effects in Neptune's atmosphere.
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DOI：
10.1038/ncomms11976
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发表时间：
2016-07-15
影响因子：
16.6
通讯作者：
Harrison RG
中科院分区：
文献类型：
--
作者：
Aplin KL;Harrison RG
在两个可见光波段对海王星亮度的长时间观测提供了其大气气溶胶的圆盘平均估计。亮度变化以前与11年的太阳周期有关，通过太阳调制机制与紫外线或银河宇宙射线（GCR）对大气粒子的影响有关。在这里，我们使用了最近扩展的亮度数据集（1972-2014），物理上逼真的建模显示，而不是替代品，紫外线和GCR可能会调制海王星的大气组合。海王星大气层对1.5- 1.9年周期的间歇性响应进一步支持了GCR的重要性，这在20世纪80年代中期优先发生在GCR（而不是紫外线）。这种周期性在地球和旅行者2号在海王星附近测量的GCR中都被检测到。海王星亮度的类似变化表明GCR离子成核。GCR和紫外线机制都可能比随后的大气粒子输送更快地发生。 从地球上观测到的海王星亮度波动背后的原因被证明是谜。在这里，Aplin和Harrison使用光度观测来表明太阳紫外线辐射和银河宇宙射线相结合是海王星大气层中起源的波动的原因。
Long-duration observations of Neptune's brightness at two visible wavelengths provide a disk-averaged estimate of its atmospheric aerosol. Brightness variations were previously associated with the 11-year solar cycle, through solar-modulated mechanisms linked with either ultraviolet or galactic cosmic ray (GCR) effects on atmospheric particles. Here, we use a recently extended brightness data set (1972–2014), with physically realistic modelling to show, rather than alternatives, ultraviolet and GCR are likely to be modulating Neptune's atmosphere in combination. The importance of GCR is further supported by the response of Neptune's atmosphere to an intermittent 1.5- to 1.9-year periodicity, which occurred preferentially in GCR (not ultraviolet) during the mid-1980s. This periodicity was detected both at Earth, and in GCR measured by Voyager 2, then near Neptune. A similar coincident variability in Neptune's brightness suggests nucleation onto GCR ions. Both GCR and ultraviolet mechanisms may occur more rapidly than the subsequent atmospheric particle transport. The causes behind fluctuations in Neptune's brightness as observed from Earth have proved enigmatic. Here, Aplin and Harrison use photometric observations to show that solar ultraviolet radiation and galactic cosmic rays combined are responsible for the fluctuations originating in Neptune's atmosphere.