The complete spectrum of the equatorial electrojet related to solar tides: CHAMP observations
The complete spectrum of the equatorial electrojet related to solar tides: CHAMP observations
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DOI：
10.5194/angeo-31-1315-2013
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发表时间：
2013-08
影响因子：
1.9
通讯作者：
H. Lühr;C. Manoj
中科院分区：
文献类型：
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作者：
H. Lühr;C. Manoj
抽象的。根据 CHAMP 卫星 10 年的磁场测量，我们绘制了赤道电喷流 (EEJ) 潮汐变化的详细图像。首次编制了与平均太阳潮汐相关的完整 EEJ 光谱。产生的频谱的很大一部分与白天和夜间 EEJ 的打开/关闭有关。在解释结果时已仔细考虑了这种效应。正如预期的那样，最大振幅是由代表平均日变化的潮汐迁移引起的。每日变化的高次谐波显示幅度有 1/f 下降。需要这样的频谱来表示 EEJ 电流在夜间的消失。迁徙潮汐信号表现出明显的年度变化，在 12 月至日和春分季节振幅较大，但在 6 月至 7 月左右减弱了 1.7 倍。推断出一系列丰富的非迁移潮汐效应。最突出的是八月左右的四峰纵向图案。几乎 90% 的结构可归因于日间向东传播的潮汐 DE3。此外，向西传播的 DW5 正在促成第 4 波。第二大非迁移潮是 12 月至日左右的半日潮 SW4。它在卫星观测中引起了第二波特征。通常被认为是十二月季节典型特征的三峰纵向形态明显较弱。在 5 月至 6 月左右的几个月里，出现了一个突出的第一波特征。对于一阶，它代表静止行星波 SPW1，导致西经 60° 以上的 EEJ 增强，并在非洲/印度上空减弱。此外，显着的三日非迁移潮 TW4 导致 EEJ 较晚在西段于当地时间 14:00 后达到峰值。一个特别有趣的非迁移潮汐是半日潮 SW3。它在 10 月到 12 月期间引起最大的 EEJ 振幅。该潮汐分量显示出对太阳通量水平的强烈依赖性，并且随着太阳最大值的幅度增加。我们不知道之前有任何研究提到 SW3 的这种行为。本研究的主要重点是展示观测到的 EEJ 频谱及其与潮汐驱动的关系。对于几个已识别的光谱成分，我们无法为生成机制提供令人信服的解释。
Abstract. Based on 10 yr of magnetic field measurements by the CHAMP satellite we draw a detailed picture of the equatorial electrojet (EEJ) tidal variations. For the first time the complete EEJ spectrum related to average solar tides has been compiled. A large fraction of the resulting spectrum is related to the switch on/off of the EEJ between day and night. This effect has carefully been considered when interpreting the results. As expected, largest amplitudes are caused by the migrating tides representing the mean diurnal variation. Higher harmonics of the daily variations show a 1/f fall-off in amplitude. Such a spectrum is required to represent the vanishing of the EEJ current at night. The migrating tidal signal exhibits a distinct annual variation with large amplitudes during December solstice and equinox seasons but a depression by a factor of 1.7 around June–July. A rich spectrum of non-migrating tidal effects is deduced. Most prominent is the four-peaked longitudinal pattern around August. Almost 90% of the structure can be attributed to the diurnal eastward-propagating tide DE3. In addition the westward-propagating DW5 is contributing to wave-4. The second-largest non-migrating tide is the semi-diurnal SW4 around December solstice. It causes a wave-2 feature in satellite observations. The three-peaked longitudinal pattern, often quoted as typical for the December season, is significantly weaker. During the months around May–June a prominent wave-1 feature appears. To first order it represents a stationary planetary wave SPW1 which causes an intensification of the EEJ at western longitudes beyond 60° W and a weakening over Africa/India. In addition, a prominent ter-diurnal non-migrating tide TW4 causes the EEJ to peak later, at hours past 14:00 local time in the western sector. A particularly interesting non-migrating tide is the semi-diurnal SW3. It causes largest EEJ amplitudes from October through December. This tidal component shows a strong dependence on solar flux level with increasing amplitudes towards solar maximum. We are not aware of any previous studies mentioning this behaviour of SW3. The main focus of this study is to present the observed EEJ spectrum and its relation to tidal driving. For several of the identified spectral components we cannot offer convincing explanations for the generation mechanisms.