Unusual nighttime impulsive foF2 enhancement below the southern anomaly crest under geomagnetically quiet conditions
Unusual nighttime impulsive foF2 enhancement below the southern anomaly crest under geomagnetically quiet conditions
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DOI：
10.1029/2011ja016593
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发表时间：
2011-12
影响因子：
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通讯作者：
M. Pezzopane;P. Fagundes;L. Ciraolo;E. Correia;M. Cabrera;R. Ezquer
中科院分区：
文献类型：
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作者：
M. Pezzopane;P. Fagundes;L. Ciraolo;E. Correia;M. Cabrera;R. Ezquer
[1]2010年3月6日，在南美洲赤道异常南峰以下的广阔区域，在太阳活动低和地磁平静的条件下，观测到了一个不寻常的夜间脉冲电子密度增强。这一现象几乎是通过在空间广泛分布的三个电离层台站，即卡舒埃拉保利斯塔观测站记录的F2层临界频率（foF2）同时观测到的（南纬22.4度，西经44.6度，磁纬13.4度），圣何塞多斯坎波斯（南纬23.2度，西经45.9度，磁纬14.1度），以及阿根廷的图库曼（南纬26.9度，西经65.4度，磁纬16.8度）。虽然是在图库曼上空一个较为有限的区域，但利用12个全球定位系统接收器的测量结果计算出的总电子含量图也观测到了这一现象。研究的现象是非常特殊的，因为除了短暂的持续时间，它的特点是一个明显的电离层压缩。通过上述电离层台站记录的F区底部的虚拟高度（h′F），以及通过计算出的图库曼上空的垂直电子密度剖面和板块厚度，都可以清楚地看到这种压缩。因此，增强的喷泉效应和等离子体扩散都不能被认为是这一不寻常事件的单一原因。等高度线和等电离层探测仪图的全面分析表明，重力波（GW）传播引起的电离层扰动（TID）可能在造成这种现象方面发挥了重要作用。
[1] An unusual nighttime impulsive electron density enhancement was observed on 6 March 2010 over a wide region of South America, below the southern crest of the equatorial anomaly, under low solar activity and quiet geomagnetic conditions. The phenomenon was observed almost simultaneously by the F2 layer critical frequency (foF2) recorded at three ionospheric stations which are widely distributed in space, namely Cachoeira Paulista (22.4°S, 44.6°W, magnetic latitude 13.4°S), Sao Jose dos Campos (23.2°S, 45.9°W, magnetic latitude 14.1°S), Brazil, and Tucuman (26.9°S, 65.4°W, magnetic latitude 16.8°S), Argentina. Although in a more restricted region over Tucuman, the phenomenon was also observed by the total electron content (TEC) maps computed by using measurements from 12 GPS receivers. The investigated phenomenon is very particular because besides being of brief duration, it is characterized by a pronounced compression of the ionosphere. This compression was clearly visible both by the virtual height of the base of the F region (h′F) recorded at the aforementioned ionospheric stations, and by both the vertical electron density profiles and the slab thickness computed over Tucuman. Consequently, neither an enhanced fountain effect nor plasma diffusion from the plasmasphere can be considered as the single cause of this unusual event. A thorough analysis of isoheight and isofrequency ionosonde plots suggest that traveling ionospheric disturbances (TIDs) caused by gravity wave (GW) propagation could have likely played a significant role in causing the phenomenon.