低纬电离层f_0F_2夜间增强的模拟研究

MODELING STUDY OF NIGHT-TIMEENHANCEMENTS IN f_0F_2 AT LOW-LAfITUDES

以太阳活动低年冬季为代表，利用二维中低纬电离层理论模式模拟低纬电离层ｆ０Ｆ２夜间增强现象。探索在赤道异常驼峰纬度附近形成该现象的可能因素或物理机制．模式在给定磁子午面内求解等离子体输运方程，给出电子及各离子的浓度、速度的时空分布、在所考察条件下，低纬驼峰纬度附近ｆ０Ｆ２模式值夜间出现了明显的增强特征．在白天峰值电子浓度较高情形下ｆ０Ｆ２夜间增强峰幅度较大。与观测统计结果一致、模拟计算结果还表明：Ｅ×Ｂ垂直漂移和中性风等因素引起的等离子体输运在驼峰纬度附近ｆ０Ｆ２夜间增强形成过程中起着很重要的作用．

The nighttime anomalous enhancements in f0FZ are simulated in this paperusing a 2D low-latitude ionospheric theoretical model. The number densities, velocities of ions and electrons are calculated in the model by solving the plasmatransport equations. Typical characteristics of pre-midnight and post-midnight increases appeared in the values of calculated f0F2 near the equatorial anomaly crestlatitudes. The larger the peak electron densities, the stronger the enhancement is,which is in consistent with observed results. It is shown that the transport of plasmainduced by E x B vertical drift and the field-aligned neutral winds is important inthe formation of nighttime increases in f0F2 at crest latitudes.