Patterns of F2-layer variability
Patterns of F2-layer variability
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DOI：
10.1016/s1364-6826(01)00036-0
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发表时间：
2001-10
影响因子：
1.9
通讯作者：
H. Rishbeth;M. Mendillo
中科院分区：
文献类型：
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作者：
H. Rishbeth;M. Mendillo
电离层在广泛的时间尺度上表现出变化，从小时和天数的运作时间尺度到太阳周期或更长时间。我们使用来自13个站的电离层探空仪数据来研究峰值F2层电子密度NmF2的逐日变异性，我们用它来定义对当地时间、季节和太阳周期的变异性的定量描述。平均而言，对于中等太阳活动年份(太阳分米通量约为140个单位)，NmF2的日波动在白天有20%的标准偏差，在夜间有33%。我们研究和讨论了电离层和地磁变化的行为模式，特别是赤道分峰。为了进一步分析，我们集中在一个典型的中纬度站，斯劳。结果表明，SLough NmF2的昼夜标准差随数据集长度的增加而先增大，在10-20天时基本不变，然后由于季节变化而进一步增大(特别是在春分时)。我们发现了一些两天波的证据，但它们似乎不是斯劳F2层的主要特征。综合地磁和电离层资料，并考虑太阳和地磁参数的逐日变化，我们发现，F2层的变化很大一部分与地磁活动有关，其余的归因于大气低层的气象来源。我们认为，夜间变化较大是由于极光能量输入增加，以及缺乏白天存在的对F2层的强烈光化学控制。
The ionosphere displays variations on a wide range of time-scales, ranging from operational time-scales of hours and days up to solar cycles and longer. We use ionosonde data from thirteen stations to study the day-to-day variability of the peak F2-layer electron density, NmF2, which we use to define quantitative descriptions of variability versus local time, season and solar cycle. On average, for years of medium solar activity (solar decimetric flux approximately 140 units), the daily fluctuations of NmF2 have a standard deviation of 20% by day and 33% by night. We examine and discuss the patterns of behaviour of ionospheric and geomagnetic variability, in particular the equinoctial peaks. For further analysis we concentrate on one typical midlatitude station, Slough. We find that the standard deviations of day-to-day and night-to-night values of Slough NmF2 at first increase with increasing length of the dataset, become fairly constant at lengths of 10–20 days and then increase further (especially at equinox) because of seasonal changes. We found some evidence of two-day waves, but they do not appear to be a major feature of Slough's F2 layer. Putting together the geomagnetic and ionospheric data, and taking account of the day-to-day variability of solar and geomagnetic parameters, we find that a large part of F2-layer variability is linked to that of geomagnetic activity, and attribute the rest to ‘meteorological’ sources at lower levels in the atmosphere. We suggest that the greater variability at night is due to enhanced auroral energy input, and to the lack of the strong photochemical control of the F2-layer that exists by day.