热层钠及突发钠层的机制研究

发布时间：2018-03-19 20:03

本文选题：钠荧光测风测温激光雷达　切入点：突发钠层　出处：《中国科学技术大学》2017年博士论文　论文类型：学位论文

【摘要】：中间层顶及低热层(80-105 km)是大气的一个过渡区域,由于太阳辐射的影响,该区域存在短期(周日变化,半日变化)及长期(大气年震荡,半年震荡)变化,并受太阳11年活动周期影响。另外中间层及低热层区域的大气成分也十分复杂,它不只有大气中的中性成分(氧气分子和氮气分子),由于这个高度有很强的光解作用,会产生大量的氧原子,另外由于流星常年飞过该区域时发生流星消融过程,在该区域注入很多金属粒子(例如:钠、铁、钾等),使得该区域形成了一个金属层。这些金属层的密度不仅会受动力学过程影响,同时还会受到化学过程的影响。钠荧光测风测温激光雷达,利用金属原子荧光共振散射,可以同时测量中间层顶及低热层(MLT,Mesopause and Lower Thermosphere)区域的温度,风场及中性钠原子密度。在钠原子层某些高度,钠原子的密度会突然增加几倍甚至十几倍并持续几分钟到几小时,这种现象称为突发钠层。另外,最近在110-160公里高度,激光雷达观测到有中性金属原子存在,且金属原子密度很低,这种现象叫做热层金属层。本论文利用两套钠荧光测风测温激光雷达(]、中国合肥;2、智利)的观测对突发钠层及热层钠原子层的形成机制进行研究。利用中国合肥中国科学技术大学自主研制的钠测风测温激光雷达、武汉流星雷达及卫星数据对一次重力波破碎及其之后发生的钠层突发现象进行个例研究。发现该次重力波破碎事件影响范围较广,对大气风场和温度场有很强的作用。重力波破碎45分钟之后,发生了的钠层突发现象,突发钠层首先在激光雷达西向通道被观测到,两分钟之后才在东向通道出现,出现高度及强度都有延迟,且该延迟持续一段时间,由此我们认为该次突发钠层事件应该是一次高密度钠原子团传输形成的,根据激光雷达及流星雷达的大气风场数据,对该钠原子团的传输方向、传输速度及水平尺度等参数进行了分析。美国Embry-Riddle Aeronautical University在智利的钠测温测风激光雷达,于2015年4月连续观测到热层钠原子层现象,同时首次得到110-140km连续观测的大气风场数据。利用TIEGCM模式与激光雷达观测的大气风场进行对比,我们发现模式可以很好的模拟观测的风场结果。利用模式水平风我们对热层钠原子层的成因进行了研究,经过分析,我们发现热层钠出现在离子最大发散区附近,这说明钠离子-电子中和理论无法解释智利观测到的热层钠原子层现象(因为钠离子-电子中和理论需要在离子汇聚区发生并产生更多的钠原子)。同时我们对不同季节、不同地点的热层金属原子层进行分析,发现中低纬度的热层金属原子层大都出现在离子最大发散区附近。在120 km以上,由于空气密度很低,流星溅射过程可以直接注入金属原子,另外大气分子离子(NO+和O2+)可以通过化学反应消耗钠原子。根据以上结果,我们提出一种可能的热层钠原子层形成机制:首先流星溅射过程将金属原子注入大气中,而后在离子发散区,大气分子离子密度降低,增加钠原子的化学寿命,使得钠原子密度变大,从而被激光雷达观测到。根据这一理论,我们进行了简单模拟,模拟的热层钠原子层和观测很一致。最后,我们就热层钠原子层的传播特性进行了简单分析。
[Abstract]:The middle and upper and lower thermosphere (80-105 km) is a transition region of the atmosphere, because of the influence of solar radiation in the region, there are short-term (Sunday, semidiurnal variation) and long-term (annual atmospheric turbulence, the first half of the shock) changes, and affected by the sun 11 year cycle of activity. In addition the middle layer and the lower thermosphere region the composition of the atmosphere is very complex, it is not only the neutral components in the atmosphere (oxygen and nitrogen molecules), because this is the height of photolysis is very strong, will produce a large number of oxygen atoms, also due to the flow of the ablation process occurred over the perennial star meteor in the region, in the region into many metal particles (such as: sodium, potassium, iron, etc.) the area formed in a metal layer. The metal layer will not only affect the density by kinetic process, but also affected by chemical process. The sodium fluorescence lidar wind temperature, using metal atomic fluorescence The resonance scattering can be measured at the same time, the middle and upper and lower thermosphere (MLT, Mesopause and Lower Thermosphere) the temperature, wind and neutral sodium atom density. In some highly sodium atomic layer, the density of sodium atoms will suddenly increase several times or even ten times and lasts a few minutes to several hours, this phenomenon is called burst the sodium layer. In addition, recently at an altitude of 110-160 km, the laser radar observed the presence of neutral metal atoms, and the metal atom density is very low, this phenomenon is called hot metal layers. This paper uses two sets of sodium fluorescence lidar (wind, Chinese Hefei; 2, Chile) observation to study the formation mechanism the sudden sodium layer and heat insulation layer. Using the sodium sodium atom wind lidar China Hefei developed by University of Science & Technology China, the Wuhan meteor radar and satellite data of a gravity wave breaking and after sodium Case studies found that the layer burst phenomenon. Gravity wave breaking events affecting a wide range, with a strong role of the atmospheric wind field and temperature field. After wave breaking 45 minutes, the sudden sodium layer phenomenon, sudden sodium layer first in the west to laser radar channel was observed after two minutes only in the East Channel, high intensity and delay, and the delay for a period of time, so we think that the sudden sodium layer events should be a high density of sodium atoms to form transmission, according to the atmospheric wind field data of laser radar and meteor radar, the transmission direction of the sodium atoms the transmission speed and the horizontal scale are analyzed. The Embry-Riddle Aeronautical University in the sodium temperature lidar in Chile in April 2015, observed a continuous layer of hot sodium layer phenomenon, and for the first time by 110- 140km atmospheric wind field data of continuous observation. Compared with the atmospheric wind field model and TIEGCM laser radar observations, we found that the simulation results of wind field observation mode can be very good. We are the causes of hot wind layer sodium atomic layer were studied using the model, through the analysis, we found that the thermal layer appears sodium in the vicinity of maximum ion divergence zone, indicating that the sodium ion electron neutralization theory cannot explain the observed thermal layer Chile sodium atom layer phenomenon (because the sodium ion - electron neutralization theory needs to produce more sodium atoms in the ion accumulation area and). At the same time we in different seasons, analyze the thermal layer of metal atomic layer in different locations the hot layer of metal atomic layer in the low latitude mostly appears in the nearby area. Ion maximum divergence is over 120 km, because the air density is very low, the meteor can be injected directly into the metal atom sputtering process, In addition the atmospheric molecular ions (NO+ and O2+) can consume sodium atoms by chemical reaction. According to the above results, we proposed a possible formation mechanism of sodium layer thermal atomic layer: the first meteor sputtering process metal atoms into the atmosphere, and then in the ion diffusion area, atmospheric molecular ion density decreases, increase the life of sodium atom chemistry so, the sodium atom density change, which was observed by laser radar. According to this theory, we conducted a simple simulation, simulation of the thermal layer sodium atomic layer and observation is very consistent. Finally, we made a simple analysis on the propagation characteristics of hot layer sodium atomic layer.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P35

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