A new aspect of ionospheric E region electron density morphology
A new aspect of ionospheric E region electron density morphology
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DOI：
10.1029/2008ja014022
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发表时间：
2009-12
影响因子：
--
通讯作者：
Y. Chu;Kong-Hong Wu;C. Su
中科院分区：
文献类型：
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作者：
Y. Chu;Kong-Hong Wu;C. Su
[1]本文根据FORMOSAT-3/COSMIC卫星对电离层电子密度剖面的全球测量，研究了E区电子密度的形态。Chapman理论很好地描述了白天E层电子密度的季节变化、纬向变化和日变化，E层峰值电子密度NmE和峰值高度hmE分别受太阳天顶角χ的控制，满足NmE <$（cosχ）p和hmE <$ln（secχ）的关系。然而，它表明，有三个地磁纬度地区的E区电子密度发生显着增强。其中一个位于地磁赤道上，纬度范围较窄，约为6° ~ 10 °;另两个纬度范围较宽，约为10° ~ 20 °，分别出现在地磁赤道两侧±20° ~ 30 °的纬度区域。这些E区密度增强的位置是不对称的地磁赤道在冬至季节，他们有一个显着的趋势，转向（远离）夏（冬）半球。赤道外E区电子密度的增强与F区赤道异常峰的底侧密切相关，在F区赤道异常峰的底侧，平行于磁力线的电子密度分量最大。看来，离赤道E区电子密度增强很可能是F区赤道异常峰的足迹。研究了χ与foE（E区临界频率）之间幂律关系中指数n和系数K的形态。在纬向区域，n和K值有冬季大于夏季的趋势，这与离赤道电子密度的增强是一致的。此外，它被发现在K值的一个小峰几乎连续地存在于所有季节的地磁赤道。比较表明，COSMIC测量和IRI模型预测之间的E区电子密度形态的显着差异。此外，还提供了令人信服的证据，表明在100-200 km高度区域存在电子密度的3、4号纵波结构，这与赤道电急流的纵向结构是一致的。认为这些纵向3峰和4峰结构很可能与电离层E区向东传播的非迁移日潮有关。
[1] From global measurements of ionospheric electron density profiles made by the FORMOSAT-3/COSMIC satellites, the morphology of E region electron density is investigated. Seasonal, latitudinal, and diurnal variations in daytime E region electron density are well described by the Chapman theory, and the E layer peak electron density NmE and its peak height hmE are governed by the solar zenith angle χ in accordance with relations NmE ∝(cosχ)p and hmE ∝ln(secχ), respectively. However, it is revealed that there are three geomagnetic latitude regions where striking enhancements of the E region electron density occur. One of them is located at the geomagnetic equator with relatively narrow latitude extent of about 6°–10°, and the other two with much wider latitude extent of about 10°–20° appear on both sides of the geomagnetic equator in latitude regions ±20°–30°, respectively. The locations of these E region density enhancements are asymmetrical about the geomagnetic equator in solstice seasons, and they have a salient tendency to shift toward (away from) the summer (winter) hemisphere. The off-equator E region electron density enhancements are closely connected with the bottomside of the F region equatorial anomaly crests, where the component of the electron density parallel to the magnetic field line is maximum. It appears that the off-equator E region electron density enhancements are very likely the footprints of the F region equatorial anomaly crests. The morphologies of the exponent n and coefficient K in the power law relation between χ and foE (E region critical frequency) are also examined. There is a tendency for the n and K values to be larger in local winter than in local summer seasons in the latitudinal regions the same as the off-equator electron density enhancements. In addition, it is found that a minor peak in the K values is nearly continuously present in all seasons over the geomagnetic equator. A comparison shows significant discrepancies in the E region electron density morphologies between COSMIC measurement and IRI model prediction. Furthermore, compelling evidence is provided to show the presences of longitudinal wave number 3 and 4 structures of the electron density in the height region 100–200 km, which are in coincident with the longitudinal structures of equatorial electrojet. It is believed that these longitudinal 3- and 4-peak structures are very likely associated with nonmigrating diurnal tides propagating eastward in ionospheric E region.