A PHYSICAL MODEL OF IONOSPHERE FOR LOW LATITUDES AND ITS' APPLICATIONS IN DISCUSSIONS OF F1 VALLEY FORMATION
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摘要: 在电离层F区考虑了三种中性成分的4种离子(O+、No+、N2+和O2+),从严格的电子和离子密度连续方程出发,由中性风所满足的动力学方程和离子运动方程解出水平中性风,从而得到离子垂直漂移速度,由此建立了一种电离层的物理模式;并用此模式,针对我国中、低纬(116°E,30°N)地区,讨论了光化学作用对F1层的影响和动力学效应在F层中的作用。着重讨论由水平中性风引起的离子垂直漂移运动对F1谷区的影响。结果表明:在光化平衡模式下,E区明显形成。在太阳活动低年夏季可产生明显的F1“凸缘”。但仅靠光化平衡作用不能产生深的F1谷区,也不能解释F2层的形成;双极扩散是F2层形成的主要机制;中性风的因素对E层影响不大,却可以在太阳活动低年夏季产生谷深在0.05—0.1的深F1谷区。用此模式还计算了F1谷区日变化,结果表明:中性风影响模式能较好地反映我国中低纬地区F1谷区变化的地域特征。Abstract: F1 valley has recently been one of the interesting issues in ionospheric F2 region.In this paper,a physical model of ionosphere for mid-and low-latitudes is taking into account self-consistently both the neutral wind and motions of ions.The speeds of neutral particles and ions are obtained by simultaneously solving sets of dynamic equations satisfied by those two kinds of particles,with are coupled through collisions.Four species of ions are included to represent photo-chemical reactions.With this ionospheric model and focusing on the area of China's central part,i.e.,116° and 30℃,the effects of photo-chemical and dynamical processes on the F2 region are discussed with particular emphasis put on the influence of ions' vertical motion on F1 valley.Results show that under photo-chemical equalibrium,E region always forms and a F1 ledge appears only in summer at low solar activity,but deep F1 valley and formation of F2 region can not be explained solely by photo-chemical process.Ambipolar diffusion is falally important for F2 formation.Vertical motions of ions caused by neutral wind does not affect E region much,but can produce a considerably profound valley in summer at low solar activity with a depth of 0.05-0.1.Diurnal variations of F1 valley is also examined and results show that this model can reflect some features of F1 valley for China's mid-and low-latitude area.
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Key words:
- F1 ledge /
- F1 valley /
- Thermo pheric wind /
- Ionospheric modelling
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