Measurement of the latitudinal distributions of total electron content during equatorial spread F events
Measurement of the latitudinal distributions of total electron content during equatorial spread F events
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赤道扩散 F 事件期间总电子含量纬度分布的测量
DOI：
10.1029/2000ja000426
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发表时间：
2001
影响因子：
--
通讯作者：
R. Sheehan
中科院分区：
文献类型：
--
作者：
C. Valladares;S. Basu;K. Groves;M. P. Hagan;D. Hysell;A. Mazzella;R. Sheehan
我们已经构建了纬度剖面的总电子含量（TEC）使用测量6个GPS接收机在1998年进行。TEC配置文件已被分为两组：一个对应的日子，当羽流或赤道扩展F（ESF）的发展，和第二组描绘的日子没有ESF的条件。ESF的存在/不存在是基于由Jicamarca无人值守长期调查（JULIA）雷达测量的相干回波的特征和来自纬度上间隔的两个地点的反气旋记录。一个闪烁站位于磁赤道附近（Ancon），另一个位于南12°（Antofagasta）。TEC的配置文件显示了典型的日常和季节性变化，在低纬度地区看到。在春分点期间，我们经常观察到距磁赤道12°至20°之间的异常峰和其间的低谷。异常出现的月分布及其出现的当地时间与已报道的垂直向上漂移的变率和目前的赤道喷泉效应理论非常一致。在春分和冬至期间，几乎每天都可以观察到TEC异常，有时是在没有ESF活动的情况下。然而，精细检查的TEC纬向配置文件表明，存在着密切的关系的TEC配置文件的时间演变接近日落和ESF的开始。我们用两种不同的方法研究了TEC的纬向分布。首先，我们计算时间差配置文件使用对应于1800和2000 LT的分布。第二，我们使用的TEC分布在2000 LT的参数化。第一种方法表明相当急剧增加的峰值和急剧下降的低谷附近在ESF天。相反，在没有ESF的日子里，在所有纬度都存在几乎一致的TEC下降。第二种方法在ESF事件期间显示出较高的波峰/波谷比（>2）、波谷处较小的TEC值和较大的纬向积分值。
We have constructed latitudinal profiles of the total electron content (TEC) using measurements from six GPS receivers conducted during 1998. The TEC profiles have been divided into two groups: One corresponds to days when plumes or equatorial spread F (ESF) develops, and the second group portrays days of no-ESF condition. The presence/absence of ESF is based on the signature of the coherent echoes measured by the Jicamarca Unattended Long-Term Investigation (JULIA) radar and records of scintillations from two sites spaced in latitude. One scintillation station is located near the magnetic equator (Ancon) and the other 12° southward (Antofagasta). The TEC profiles display the typical day-to-day and seasonal variability seen at low latitudes. During the equinoxes, we observed quite often the crests of the anomaly located between 12° and 20° away from the magnetic equator and a trough in-between. The monthly distribution of the appearance of the anomaly and the local time of their appearance are in very good agreement with the reported variability of the upward vertical drifts and the current theory of the equatorial fountain effect. During the equinoxes and the December solstice, the TEC anomaly is observed almost every day, sometimes when there is no ESF activity. Nevertheless, fine inspection of the TEC latitudinal profiles suggests the existence of a close relationship between the temporal evolution of the TEC profiles near sunset and the onset of ESF. We have examined the TEC latitudinal distributions in two different ways. First, we calculated time difference profiles using the distributions corresponding to 1800 and 2000 LT. Second, we used a parameterization of the TEC distributions obtained at 2000 LT. The first method indicates quite drastic increases of the crest values and sharp decreases near the trough during ESF days. In contrast, during days of no ESF there exist almost uniform TEC decreases at all latitudes. The second method displays a preferred high crest/trough ratio (>2), small TEC values at the trough, and large latitudinal integrated values during ESF events.