Periodic variations of oxygen EUV dayglow in the upper atmosphere of Venus: Hisaki/EXCEED observations
Periodic variations of oxygen EUV dayglow in the upper atmosphere of Venus: Hisaki/EXCEED observations
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金星高层大气中氧气 EUV 日光的周期性变化：Hisaki/EXCEED 观测
DOI：
10.1002/2015je004849
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
I.
中科院分区：
文献类型：
--
作者：
Masunaga;K.; Seki;K.; Terada;N.; Tsuchiya;F.; Kimura;T.; Yoshioka;K.; Murakami;G.; Yamazaki;A.; Kagitani;M.; Tao;C.; Fedorov;A.; Futaana;Y.; Zhang;T. L.; Shiota;D.; Leblanc;F.; Chaufray;J.-Y.; Yoshikawa;I.
利用Hisaki上的外层动力学极紫外光谱仪（EXCEED）和太阳和日光层观测站上的太阳极紫外监测器，研究了3 - 4月金星高层大气中OII 83.4nm、OI 130.4nm和OI 135.6nm极紫外日辉亮度的变化（第1期）、4月至5月（第2期）和6月至7月（第3期）。结果表明，除太阳自转效应外，日辉变化还存在特征周期：周期1为1.8，2.8，3.1，4.5和9.9d，周期2为1.1d，周期3为1.0和11 d。许多这些周期性与以前的观察和理论是一致的。我们认为这些周期性与热层中氧原子或光电子的密度振荡有关。这些周期性的原因仍然不确定，但行星尺度波和/或从中层大气传播的重力波，和/或太阳EUV辐射通量的微小周期性变化可能起作用。太阳风参数（速度、动压和行星际磁场强度）对日光变化的影响也利用金星快车上的空间等离子体和高能原子分析仪（ASPERA-4）和磁力计进行了研究。虽然没有发现与日光变化的明显相关性，但它们的小周期与日光周期相似。太阳风对日辉的贡献尚不清楚，但太阳风参数可能会影响日辉的变化。
Using the Extreme Ultraviolet Spectroscope for Exospheric Dynamics (EXCEED) aboard Hisaki and the Solar Extreme Ultraviolet Monitor on the Solar and Heliospheric Observatory, we investigate variations of the extreme ultraviolet (EUV) dayglow brightness for OII 83.4 nm, OI 130.4 nm, and OI 135.6 nm in the Venusian upper atmosphere observed in March–April (period 1), April–May (period 2), and June–July (period 3) in 2014. The result shows that characteristic periodicities exist in the dayglow variations other than the ~27 day solar rotational effect of the solar EUV flux: 1.8, 2.8, 3.1, 4.5, and 9.9 day in period 1; 1.1 day in period 2; and 1.0 and 11 day in period 3. Many of these periodicities are consistent with previous observations and theory. We suggest these periodicities are related to density oscillations of oxygen atoms or photoelectrons in the thermosphere. The cause of these periodicities is still uncertain, but planetary‐scale waves and/or gravity waves propagating from the middle atmosphere, and/or minor periodic variations of the solar EUV radiation flux may play a role. Effects of the solar wind parameters (velocity, dynamic pressure, and interplanetary magnetic field's intensity) on the dayglow variations are also investigated using the Analyser of Space Plasma and Energetic Atoms (ASPERA‐4) and magnetometer aboard Venus Express. Although clear correlation with the dayglow variations is not found, their minor periodicities are similar to the dayglow periodicities. Contribution of the solar wind to the dayglow remains still unknown, but the solar wind parameters might affect the dayglow variations.