Development of intermediate‐scale structure at different altitudes within an equatorial plasma bubble: Implications for L‐band scintillations
Development of intermediate‐scale structure at different altitudes within an equatorial plasma bubble: Implications for L‐band scintillations
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赤道等离子体气泡内不同高度的中尺度结构的发展：对 L 波段闪烁的影响
DOI：
10.1002/2016ja023478
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
S. Sunda
中科院分区：
文献类型：
--
作者：
A. Bhattacharyya;B. Kakad;P. Gurram;S. Sripathi;S. Sunda
中间尺度长度发展的一个重要方面赤道等离子体泡（EPB）中的不规则性（大约几百米到几公里），在预测低纬度地区L波段振荡发生模式的方案中没有考虑到，当EPB在日落后赤道电离层中上升时，由于瑞利-泰勒不稳定性的增长，这些结构如何在EPB内的不同高度发展。倾角赤道上不同高度的辐照度映射到不同的纬度，它们的光谱以及背景电子密度决定了不同纬度L带辐照度的强度。在本文中，VHF和L-波段在不同的纬度记录到的反气旋与反气旋的理论模型一起被用来研究这种结构的EPBs的L-波段反气旋的发生和强度在不同的纬度的影响。理论模拟表明，虽然在赤道站记录的VHF信号上的不规则性的S4指数可能>1，但在赤道电离异常（EIA）波峰附近记录的VHF信号上的不规则性的S4指数通常不超过1，因为EIA波峰附近的F层峰值处的中尺度不规则性谱比赤道F层峰值处的中尺度不规则性谱浅。这也解释了L-波段重叠的纬度分布。因此，可以得出结论，有更大的结构的EPB上的赤道F区的顶侧比附近的赤道F层峰。
An important aspect of the development of intermediate‐scale length (approximately hundred meters to few kilometers) irregularities in an equatorial plasma bubble (EPB) that has not been considered in the schemes to predict the occurrence pattern of L‐band scintillations in low‐latitude regions is how these structures develop at different heights within an EPB as it rises in the postsunset equatorial ionosphere due to the growth of the Rayleigh‐Taylor instability. Irregularities at different heights over the dip equator map to different latitudes, and their spectrum as well as the background electron density determine the strength of L‐band scintillations at different latitudes. In this paper, VHF and L‐band scintillations recorded at different latitudes together with theoretical modeling of the scintillations are used to study the implications of this structuring of EPBs on the occurrence and strength of L‐band scintillations at different latitudes. Theoretical modeling shows that while S4 index for scintillations on a VHF signal recorded at an equatorial station may be >1, S4 index for scintillations on a VHF signal recorded near the crest of the equatorial ionization anomaly (EIA) generally does not exceed the value of 1 because the intermediate‐scale irregularity spectrum at F layer peak near the EIA crest is shallower than that found in the equatorial F layer peak. This also explains the latitudinal distribution of L‐band scintillations. Thus, it is concluded that there is greater structuring of an EPB on the topside of the equatorial F region than near the equatorial F layer peak.