Ionospheric long-term trends: can the geomagnetic control and the greenhouse hypotheses be reconciled?
Ionospheric long-term trends: can the geomagnetic control and the greenhouse hypotheses be reconciled?
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电离层长期趋势：地磁控制和温室假设能否协调一致？
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
A. Mikhailov
中科院分区：
文献类型：
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作者：
A. Mikhailov
从地磁控制概念和温室假说的角度考虑电离层F2层参数的长期趋势。需要强调的是，长期地磁活动变化对于电离层长期趋势至关重要，因为它们决定了 foF2 和 hmF2 长期变化的基本自然模式。应从分析数据中去除地磁活动影响以获得电离层参数的真实趋势，但通常不这样做。只有热层冷却（被认为是中性密度下降的解释）不能与同期揭示的负 foF2 趋势相一致。需要更明显地降低 O/N2 比，而经验热层模型无法提供这一点。由于 NmF2 对中性温度的依赖性较弱，因此在 foF2 趋势中实际上看不到热层冷却；因此，foF2的趋势主要受地磁活动长期变化的控制。长期 hmF2 变化也受到地磁活动变化的控制，因为 NmF2 和 hmF2 这两个参数都与 F2 层形成机制相关。但hmF2对中性温度变化非常敏感，因此1972年后在斯劳观测到的强阻尼hmF2长期变化可以被认为是热层变冷的直接表现。早些时候揭示了西欧的负 hmF2 趋势，其中磁偏角 D 0) 可能与西向热层风有关，由于 20 世纪 60 年代末后地磁活动增加，热层冷却（CO2 增加）和加热之间的竞争，西向热层风的作用得到了增强。
The ionospheric F2-layer parameter long-term trends are considered from the geomagnetic control concept and the greenhouse hypothesis points of view. It is stressed that long-term geomagnetic activity variations are crucial for ionosphere long-term trends, as they determine the basic nat- ural pattern of foF2 and hmF2 long-term variations. The ge- omagnetic activity effects should be removed from the ana- lyzed data to obtain real trends in ionospheric parameters, but this is not usually done. Only a thermosphere cooling, which is accepted as an explanation for the neutral density decrease, cannot be reconciled with negative foF2 trends revealed for the same period. A more pronounced decrease of the O/N2 ratio is required which is not provided by empirical thermo- spheric models. Thermospheric cooling practically cannot be seen in foF2 trends, due to a weak NmF2 dependence on neutral temperature; therefore, foF2 trends are mainly con- trolled by geomagnetic activity long-term variations. Long- term hmF2 variations are also controlled by geomagnetic ac- tivity variations, as both parameters, NmF2 and hmF2 are re- lated by the F2-layer formation mechanism. But hmF2 is very sensitive to neutral temperature changes, so strongly damped hmF2 long-term variations observed at Slough after 1972 may be considered as a direct manifestation of the ther- mosphere cooling. Earlier revealed negative hmF2 trends in western Europe, where magnetic declination D 0), can be related to westward thermospheric wind whose role has been enhanced due to a competition between the thermosphere cooling (CO2 increase) and its heating under increasing geomagnetic activ- ity after the end of the 1960s.