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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Effects of station relocation in the aa index
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Effects of station relocation in the aa index

机译：站搬迁aa指数的影响

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Earlier studies have shown that the long-term measure of geomagnetic activity, the aa index, is inhomogeneous and depicts an excessively large (about 12 nT) centennial increase. This has preliminarily been suggested to be due to possible station intercalibration problems in 1957 when the northern aa station was changed from Abinger to Hartland. In the present paper we show that the 3-hourly aa index time series is not uniform but includes systematic jump-like changes in the distribution of the various aa values with each change of stations in 1920, 1926, 1957, and 1980. We estimate how large a change to the aa index was caused by each particular aa value. We find that the changes to the aa index due to different ranges of activity are smooth and fairly similar for all jumps. In 1957 the largest aa values had, at the expense of more moderate aa values, a relatively larger contribution to the jump than in other station changes because the relative station coefficient was somewhat larger in 1957, leading to larger spreading and a higher average level of aa values. However, while this difference could cause a slight overestimate of the aa values, we find that the total changes in the aa index over jumps are in agreement, in both sign and magnitude, with the solar cycle variation. So it is unlikely that the excessive increase of the aa index would be due to erroneously estimated station coefficients.
机译：早期的研究表明,长期的aa指数,衡量地磁活动的不均匀,描绘了一个特别大的(约12元)纪念增加。初步认为是由于可能相互校准问题1957年北方aa站了从产品到一起。显示,3小时aa指数时间序列没有统一,但是包括系统的弹跳各种aa的分布的变化值与每一个站在1920年的变化,1926、1957和1980。aa指数是由每一个变化特定的aa的价值。aa指数由于不同范围的活动是光滑的和相当类似的跳跃。1957年最大的aa值,为代价的更温和aa值,一个相对更大贡献比其他跳站相对站,因为变化系数1957年略大,导致更大的吗传播和aa的平均水平更高值。导致轻微高估aa的价值观,我们发现总aa指数的变化跳跃在协议,标志和级,太阳周期变化。不太可能的过度增加aa指数会由于错误估计站系数。

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