Comparison of fine structures of electron cyclotron harmonic emissions in aurora
Comparison of fine structures of electron cyclotron harmonic emissions in aurora
复制标题
极光电子回旋谐波发射精细结构比较
DOI：
10.1002/2015ja021631
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
M. Dundek
中科院分区：
文献类型：
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作者：
J. Labelle;M. Dundek
最近在日光条件下发现了极光中的高次谐波回旋辐射，这促使南极南极站的无线电接收器进行了修改，以测量2013-2014年和2014-2015年连续两个南方夏季这种辐射的精细结构。该实验在376天的观测中记录了347次发射事件。这些事件的季节分布表明，如果它们在匹配条件fuh = Nfce下产生，则更高的谐波需要更高的太阳天顶角才能出现，这是预期的，对于更高的N需要更高的电子密度，这与更高的太阳天顶角相关。这一结果表明，通过波-波过程从低次谐波产生高次谐波只能解释少数事件。对21个两次谐波同时发生的情况的详细研究表明，在几乎所有事件中，高次谐波都来自较高的海拔，只有在一小部分事件中，发射的精细结构的频率是相关的，并且是精确的整数比。这一观测结果给出了发射部分15-20%的上界，这部分可以用在fce处涉及Z模波的波-波相互作用来解释，并且结合源高度的考虑，给出了在2fce处Z模波聚并解释的部分的上界为75%。综上所述，这些结果表明，高次谐波的主要机制是在匹配点fuh = Nfce处独立产生，波-波相互作用机制解释了相对较小的一部分事件。
Recent discoveries of higher harmonic cyclotron emissions in aurora occurring under daylight conditions motivated the modification of radio receivers at South Pole Station, Antarctica, to measure fine structure of such emissions during two consecutive austral summers, 2013–2014 and 2014–2015. The experiment recorded 347 emission events over 376 days of observation. The seasonal distribution of these events reveals that successively higher harmonics require higher solar zenith angles for occurrence, as expected if they are generated at the matching condition fuh = Nfce, which for higher N requires higher electron densities which are associated with higher solar zenith angles. This result implies that generation of higher harmonics from lower harmonics via wave‐wave processes explains only a minority of events. Detailed examination of 21 cases in which two harmonics occur simultaneously shows that in almost all events the higher harmonic comes from higher altitudes, and only for a small fraction of events is it plausible that the frequencies of the fine structures of the emissions are correlated and in exact integer ratio. This observation puts an upper bound of 15–20% on the fraction of emissions which can be explained by wave‐wave interactions involving Z mode waves at fce and, combined with consideration of source altitudes, puts an upper bound of 75% on the fraction explained by coalescence of Z mode waves at 2fce. Taken together, these results suggest that the dominant mechanism for the higher harmonics is independent generation at the matching points fuh = Nfce and that the wave‐wave interaction mechanisms explain a relatively small fraction of events.
曙光卫星对上部电离层发出的中频/高频极光无线电发射的观测
DOI：
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发表时间：
2010
期刊：
影响因子：
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作者：
佐藤由佳;他
通讯作者：
他
4fce 极光咆哮的首次观测
DOI：
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发表时间：
2011
期刊：
影响因子：
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作者：
佐藤由佳;小野高幸;佐藤夏雄;小川泰信
通讯作者：
小川泰信
4fce 极光咆哮排放的首次观测
DOI：
10.1029/2012gl051205
发表时间：
2012
期刊：
Geophys. Res., Lett
影响因子：
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作者：
Sato;Y.;T. Ono;N. Sato;Y. Ogawa
通讯作者：
Y. Ogawa