Statistical studies of auroral MF burst emissions observed at South Pole Station and at multiple sites in northern Canada
Statistical studies of auroral MF burst emissions observed at South Pole Station and at multiple sites in northern Canada
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南极站和加拿大北部多个地点观测到的极光中频爆发发射的统计研究
DOI：
10.1029/2004ja010608
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发表时间：
2005
影响因子：
--
通讯作者：
J. Linder
中科院分区：
文献类型：
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作者：
J. Labelle;A. Weatherwax;M. Tantiwiwat;E. Jackson;J. Linder
[1]极光MF爆发是在地面观测到的极光起源的宽带脉冲自然射电发射，频率范围为0.8-4.5 MHz。应用半自动分析方法对南极站（磁纬74°）收集的数据进行分析，得到了2003年1月1日至12月31日期间观测到的中频爆发发射的频率、振幅和世界时的数据库。除了证实，MF爆发的排放量只在黑暗中观察到在地面水平和磁当地时间在控制MF爆发的发生率，这在前磁午夜小时最大化起着重要的作用，这些数据显示，MF爆发的频率往往是更高的日落后和日出前比他们在仲冬。这一观测结果支持了发射频率与电离层中最大等离子体频率之间的联系。南极数据还显示，MF爆发的频率远低于电离层的陀螺频率，这带来了他们的可能性，部分在哨声模式。从一个超低频MF爆发的例子的光学和riometer数据的分析表明，MF爆发是与一个相对较高的能量（>10千电子伏）的极光电子束。1997-1998年加拿大多个天文台的观测资料表明，MF爆发发生率在磁纬74°附近最大。在观测站间距为260-585 km的情况下，大约10%的MF爆发事件在两个或更多个站被观测到。在符合事件中，约有3/4首先发生在低纬站，然后转移到高纬站。在两个或两个以上的观测站检测到的MF爆发事件的平均持续时间随着纬度的增加而增加。
[1] Auroral MF burst is a broadband impulsive natural radio emission of auroral origin observed at ground level in the frequency range 0.8–4.5 MHz. Application of a semiautomated analysis method to data collected at South Pole Station, 74° magnetic latitude, results in a database of frequencies, amplitudes, and universal times of MF burst emissions observed during 1 January–31 December 2003. Besides confirming that MF burst emissions are observed at ground level only during darkness and that magnetic local time plays a significant role in controlling the MF burst occurrence rate, which maximizes in the pre-magnetic-midnight hours, these data reveal that the frequencies of MF burst emissions tend to be higher just after sunset and before sunrise than they are during midwinter. This observation supports a link between the emission frequency and the maximum plasma frequency in the ionosphere. South Pole data also show evidence for MF burst extending to frequencies well below the ionospheric gyrofrequency, which brings up the possibility that they are partly in the whistler mode. Analysis of optical and riometer data from one extra-low-frequency MF burst example suggests that MF burst is associated with a relatively high-energy (>10 keV) auroral electron beam. Data from multiple Canadian observatories during 1997–1998 show that the MF burst occurrence rate maximizes near 74° magnetic latitude. With observatories spaced by 260–585 km, about 10% of the MF burst events are observed at two or more stations. Among coincident events, about 3/4 occur first at the lower-latitude station and shift to the higher-latitude station. The average duration of the MF burst events detected at two or more observatories increases with latitude.