| Polar mesosphere is a unique environment with icy dust grains to form a dusty plasma which causes the abnormal polar radar echoes composed of PMSE,PMWE,Es,NLC,etc.This thesis discusses the physical trait and the cause of abnormal echoes of the area from experimental data and theoretical models.Discovered that Es radar echoes have some subtle “peak shift” in UHF radar frequency.Found that under the influence of high energy electron precipitation the intensity of PMSE radar echo in UHF has dominant contact with the ratio of radar volume reflectivity coefficient to frequency's logarithm;Through theoretical simulation obtained that the radiation pressure of the sun to icy dust grains has the same order of magnitude with gravity,and can be resolved into light drag force towards the sun and the lateral force which causes spin moment.The main work is as follows:1.Start with the mechanism of incoherent scatter radar,introducing the concept of backscattering cross section to export radar equation,explained some of PMSE's basic characteristics incarnated in radar data : electron density “bite-out”,frequency dependency,etc.Take a full-day complete experiment with incoherent scatter radar in Troms?,Norway as example,the traits of frequency dependency and direction sensitivity are drew forth and given interpretation conformed to the theories.There is a lack of comparison between Sporadic-E(Es)echoes in UHF and VHF.Based on 2007,08,15 EISCAT observation data,a classical Es is compared of its similarity and differentiation to double frequency's echo traits.The similarity conforms to existing theories,yet discrete to what is generally deemed,Es also has a frequency dependency to some extent.Constrastive analyzes made it clear that there exists wispy “peak shift” under different frequencies.The cause of Es should have some resemblance to the one which has notable frequency dependency of PMSE in hint,awaiting further theoretical studies around the academic circle.2.In view of several main theories of PMSE origin,such as negative feedback of particle growth,gas turbulence and stratified medium,the core ideas are briefly explained.Instructions on PMSE area routine observations,and outside of the artificial heating experiment is important in the simulation results of the simulation of microwave heating experiment after finishing summary,waves of 2006 China joined the European an artificial joint after the incoherent scattering radar heating experiment,at the same time in the UHF and VHF made detailed introduction and observation data is given adequate comparison and analysis.This is the first time China has full of PMSE phenomenon under the UHF radar observation record,record the complete artificial heating overshoot,finely analyzes the reflectivity and the frequency of inner link,support hierarchical structure of objective existence.3.From the creative thought of light pressure from solar radiation to the polar icy dust grains,this paper considers the radius distribution of near spherical particles,and establish optical models for simulating calculation.Qualitatively and quantitatively to some extent theoretically the influence of dynamics of its and the crystal grains to discuss,ice crystals dust particles are drawn toward the sun and the light of the same order of magnitude of gravity stress,and under the action of lateral radiation pressure have rotational moment of conclusion,for its height distribution under the influence of electromagnetic force and background wind,the Alfonso wave effect caused by vertical transport is presumed,which is convenient for further research in the future,and helps to explain the phenomena of PMSE and other phenomena. |
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