Trends in the solar quiet geomagnetic field variation linked to the Earth's magnetic field secular variation and increasing concentrations of greenhouse gases
Trends in the solar quiet geomagnetic field variation linked to the Earth's magnetic field secular variation and increasing concentrations of greenhouse gases
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DOI：
10.1029/2009ja015136
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发表时间：
2010-08
影响因子：
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通讯作者：
A. Elias;M. M. Z. Artigas-M.;B. Barbas
中科院分区：
文献类型：
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作者：
A. Elias;M. M. Z. Artigas-M.;B. Barbas
[1]结合地球磁场的长期变化和温室气体浓度的增加，研究了太阳静止地磁场变化(Sq)的长期趋势。SQ主要是由在E区流动的电离层电流系统引起的，除其他变量外，还取决于电离层电导率。这些电导率反过来又取决于地球的主磁场(B)和E区的电子浓度，对于E区，FOE是其峰值的量度。由于B表现出长期变化，因此SQ的长期变化是可以预料的。另一个能够引起SQ趋势的可能机制是温室气体浓度的增加，这会在高层大气中产生冷却效应，并且根据模型预测和实验结果，FOE有增加的趋势。为了检测上述两种机制是否能够引起Sq的趋势，分析了三个地磁观测站(Apia、Fredericksburg和Hermanus)在1960-2001年期间的水平强度(H)的Sq变化，其中B是减小的。我们发现了显著的增长趋势(分别为6.6%、5.4%和9.9%)，这可能部分是由各自站点的B长期变化造成的。从理论上预测的FOE增长预期的SQ趋势很低(∼0.5%)，尽管是积极的，正如观察到的趋势一样。
[1] Long-term trends in solar quiet geomagnetic field variation (Sq) are studied in connection to the Earth's magnetic field secular variations and increasing greenhouse gas concentrations. Sq is mainly caused by ionospheric current systems that flow in the E region and depends, among other variables, on the ionospheric conductivities. These conductivities in turn depend on the Earth's main magnetic field (B) and the electron concentration in the E region, for which foE is a measure of its peak value. Since B shows secular variation, induced long-term changes in Sq might be expected. Another possible mechanism that would be able to induce Sq trends is the increasing concentrations of greenhouse gases that produce a cooling effect in the upper atmosphere and, according to model predictions and experimental results, an increasing trend in foE. To detect if both mechanisms mentioned are able to induce trends in Sq, the Sq variation of the horizontal intensity (H) of three magnetic observatories (Apia, Fredericksburg, and Hermanus), for which B is decreasing, is analyzed for the period 1960–2001. We find significant increasing trends (6.6%, 5.4%, and 9.9%, respectively) which may be partially accounted for by B secular variations in the respective sites. The Sq trend expected from the theoretically predicted foE increase is low (∼0.5%), although positive, as is the observed trend.