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Short‐Term Variability of Equatorial Electrojet Modulation by Solar Tidal and Planetary Waves, as Derived From the Swarm Constellation
Journal of Geophysical Research: Space Physics ( IF 2.8 ) Pub Date : 2021-04-29 , DOI: 10.1029/2020ja028884
Hermann Lühr 1 , Yun‐Liang Zhou 2 , Patrick Alken 3, 4
Affiliation  

ESA’s constellation mission Swarm with its three identical spacecraft allows the separation of spatial and temporal variations of wave phenomena. Here we investigate the modulation of the equatorial electrojet (EEJ) amplitude by solar tides and planetary waves. This is the first study to exploit the short‐term variability of these signals in the EEJ. Based on 6‐day data sets of quasi‐simultaneous observations from the well separated Swarm A and Swarm B spacecraft we derive amplitudes and phases of solar tides and prominent planetary waves. Tidal amplitudes can vary by a factor of 2 from week to week. Conversely, the phases of the tides show steady changes, suggesting a stable tidal system. Simultaneous observations at different local times return quite different wave forms, suggesting local time dependent amplitude changes of the tidal signatures in EEJ. DE3 signatures get weak toward evening, while DE2 is strongest around 15:00 magnetic local time. Modulation of the EEJ by planetary waves up to 6 days is also analyzed. Clearly dominating is the westward propagating quasi‐6‐day wave. Derived amplitudes are largest around September and exhibit a secondary occurrence maximum at spring time. Generally, the influence of this planetary wave on the EEJ hardly reaches 30% of that caused by solar tides. For the first time we monitor the influence of eastward propagating ultra‐fast Kelvin waves at 2–3 days period on the EEJ. Related activity occurs sporadically at intervals of 1–4 months and the effects on the EEJ are even smaller than that from the 6‐day wave.

中文翻译:

群体星座图推导的太阳潮汐和行星波对赤道电喷调制的短期变化

ESA的星座任务Swarm及其三个相同的航天器允许分离波动现象的时空变化。在这里,我们研究太阳潮和行星波对赤道电喷(EEJ)振幅的调制。这是第一个利用这些信号在EEJ中的短期可变性的研究。根据来自完全分开的Swarm A和Swarm B航天器的六天同时观测数据集,我们得出了太阳潮和突出的行星波的振幅和相位。每周的潮汐幅度可能相差2倍。相反,潮汐的相位显示出稳定的变化,表明潮汐系统稳定。在不同的当地时间进行的同时观测会返回完全不同的波形,提示EEJ中潮汐信号的局部随时间变化的幅度变化。傍晚时分,DE3信号减弱,而当地时间15:00左右,DE2信号最强。还分析了长达6天的行星波对EEJ的调制。显然是占主导地位的是向西传播的准6天波。导出的振幅在9月前后最大,并且在春季显示出次生的最大值。通常,该行星波对EEJ的影响几乎不会达到由太阳潮引起的影响的30%。我们首次监测了在2-3天期间向东传播的超快开尔文波对EEJ的影响。相关活动偶尔发生,间隔为1-4个月,对EEJ的影响甚至小于6天波动。而DE2在当地时间15:00磁性最强。还分析了长达6天的行星波对EEJ的调制。显然是占主导地位的是向西传播的准6天波。导出的振幅在9月前后最大,并且在春季显示出次生的最大值。通常,该行星波对EEJ的影响几乎不会达到由太阳潮引起的影响的30%。我们首次监测了在2-3天期间向东传播的超快开尔文波对EEJ的影响。相关活动偶尔发生,间隔为1-4个月,对EEJ的影响甚至小于6天波动。而DE2在当地时间15:00磁性最强。还分析了长达6天的行星波对EEJ的调制。显然是占主导地位的是向西传播的准6天波。导出的振幅在9月前后最大,并且在春季显示出次生的最大值。通常,该行星波对EEJ的影响几乎不会达到由太阳潮引起的影响的30%。我们首次监测了在2-3天期间向东传播的超快开尔文波对EEJ的影响。相关活动偶尔发生,间隔为1-4个月,对EEJ的影响甚至小于6天波动。导出的振幅在9月前后最大,并且在春季显示出次生的最大值。通常,该行星波对EEJ的影响几乎不会达到由太阳潮引起的影响的30%。我们首次监测了在2-3天期间向东传播的超快开尔文波对EEJ的影响。相关活动偶尔发生,间隔为1-4个月,对EEJ的影响甚至小于6天波动。导出的振幅在9月前后最大,并且在春季显示出次生的最大值。通常,该行星波对EEJ的影响几乎不会达到由太阳潮引起的影响的30%。我们首次监测了在2-3天期间向东传播的超快开尔文波对EEJ的影响。相关活动偶尔发生,间隔为1-4个月,对EEJ的影响甚至小于6天波动。
更新日期:2021-05-17
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