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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Temporal properties of magnetospheric line radiation
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Temporal properties of magnetospheric line radiation

机译：磁层线辐射的时间特性

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摘要

Magnetospheric line radiation (MLR) events are relatively narrowband VLF signals that sometimes drift in frequency and have been observed in both ground-based and satellite data sets. We present the results of a survey undertaken on the basis of measurements made of MLR events observed at Halley, Antarctica (75 degrees 30'S, 26 degrees 54'W, L approximate to 4.3), in June, July, September, and December 1995, specifically looking at the temporal properties of Halley MLR events. We find that (1) single MLR lines described in previous papers tend to be comprised of up to 3 lines with widths of 5-10 Hz. (2) The multiple lines show highly variable spacings (e.g., < 10 to similar to 100 Hz). (3) The rate at which MLR lines appears from the noise is similar to 0.1 to 0.2 dB s(-1), considerably smaller than previously reported for other VLF emissions; MLR exhibits slow growth, relative frequency stability, and long lifetimes in comparison with other coherent whistler mode emissions and thus may be generated by a separate mechanism. (4) The diurnal occurrence of MLR observed at Halley is twin-peaked, indicating an association with a combination of chorus and midlatitude hiss. (5) MLR occurrence rates can vary greatly within a given month, but the proportion of MLR present as part of the overall Halley wave activity is roughly constant (10-13%) throughout the year. (6) The occurrence of MLR activity at Halley is weakly linked to geomagnetic activity but only 24-48 hours after very large storms (Kp > 6), which affects only 8% of the total MLR events in this study. For smaller storms, there is little effect, although MLR events tend not to occur when the geomagnetic activity has been quiet in the previous 48 hours. (7) There is no dependence of MLR occurrence rates upon the instantaneous levels of geomagnetic activity. (8) The average duration of a typical MLR event at Halley is similar to 30 min, quite similar to previous reports. [References: 27]
机译：磁层线辐射（MLR）事件是相对窄带的VLF信号，有时会发生频率漂移，并且已在地面和卫星数据集中观察到。我们提供的调查结果是基于对1995年6月，7月，9月和1995年南极州哈雷（南纬75度，南纬26度，54度，L值约为4.3）观测到的MLR事件进行的测量而得出的，特别关注哈雷MLR事件的时间特性。我们发现（1）先前论文中描述的单条MLR线往往由多达3条线组成，宽度为5-10 Hz。 （2）多行显示高度可变的间距（例如，<10到100 Hz相似）。 （3）来自噪声的MLR线出现的速率类似于0.1到0.2 dB s（-1），比以前报道的其他VLF发射要小得多;与其他相干的惠斯勒模式发射相比，MLR表现出缓慢的增长，相对的频率稳定性和长的使用寿命，因此可能是由单独的机制生成的。 （4）在哈雷观测到的MLR的昼夜是双峰的，表明与合唱和中纬度嘶嘶声有关。 （5）在给定的月份内，MLR发生率变化很大，但全年中，作为总哈雷波活动一部分的MLR比例大致保持恒定（10-13％）。 （6）哈雷MLR活动的发生与地磁活动之间存在微弱的联系，但是在非常大的风暴之后（Kp> 6）仅在24-48小时后发生，这仅影响本研究中总MLR事件的8％。对于较小的风暴，几乎没有影响，尽管在过去48小时内地磁活动处于安静状态时，MLR事件往往不会发生。 （7）MLR的发生率与地磁活动的瞬时水平无关。 （8）在哈雷，典型的MLR事件的平均持续时间类似于30分钟，与以前的报告非常相似。 [参考：27]

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