Average field-aligned ion velocity over the EISCAT radars
Average field-aligned ion velocity over the EISCAT radars
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EISCAT 雷达上的平均场对准离子速度
DOI：
10.1002/2017ja023974
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
and Y. Ogawa
中科院分区：
文献类型：
--
作者：
Yamazaki;Y.;M. J. Kosch;and Y. Ogawa
欧洲非相干散射（EISCAT）雷达在特罗姆瑟（69.6°N，19.2°E）和斯瓦尔巴（78.2°N，16.0°E）的长期测量被用来确定高纬度F区电离层（175-475 km）场向离子速度的气候学。平均离子速度是在不同的海拔高度和一天中的不同时间计算的。平均场向离子速度的大小约为10 m/s，类似于先前在中低纬度的结果。这两种雷达的结果是一致的。在白天，平均场向离子速度的方向在350公里左右从向下变为向上，而在夜间，它在所有高度都是向上的。白天场向离子速度的反转高度取决于太阳活动。在高太阳通量期间，它比低太阳通量期间升高100公里以上。热层电离层电动力学大气环流模式再现了场向离子速度气候学的主要特征。模拟结果表明，等离子体压力梯度力和重力对白天场向离子运动起主导作用。场向离子速度的高度模式在恒定压力表面的不同太阳活动条件下倾向于保持不变，但在恒定高度下则不然，这解释了观察到的对太阳活动的依赖性。在夜间，中性风的影响主导了场向离子速度。
Long‐term measurements by the European Incoherent Scatter (EISCAT) radars at Tromsø (69.6°N, 19.2°E) and Svalbard (78.2°N, 16.0°E) are used to determine the climatology of the field‐aligned ion velocity in theFregion ionosphere (175–475 km) at high latitudes. The average ion velocity is calculated at various altitudes and times of day. The magnitude of the average field‐aligned ion velocity is on the order of 10 m/s, similar to previous results at middle and low latitudes. The results obtained for the two radars are in good agreement. During daytime the direction of the average field‐aligned ion velocity changes from downward to upward around 350 km, while during nighttime it is upward at all heights. The reversal height of the daytime field‐aligned ion velocity depends on solar activity. It is elevated by more than 100 km during high solar flux periods compared to low solar flux periods. The Thermosphere Ionosphere Electrodynamics General Circulation Model reproduces the main features of the field‐aligned ion velocity climatology. The simulation results suggest that the plasma pressure gradient force and gravity force play a dominant role for the daytime field‐aligned ion motion. The height pattern of the field‐aligned ion velocity tends to be preserved in different solar activity conditions at constant pressure surfaces, but not at constant altitudes, which explains the observed dependence on solar activity. During nighttime, the effect of the neutral wind dominates the field‐aligned ion velocity.