The Key Technology Of Solar K-corona Detection

Corona is the outermost layer of the solar atmosphere.It is the places where the physical process related to coronal heating and solar eruptions take place,and thus observing corona is the key to the physics works.K corona is part of the white-light corona,which consists of free electrons and exhibits a linearly polarized continuous spectrum owing to Thomson scattering,by the electrons,of light from the photosphere.The formation of the K corona indicates that it is extremely sensitive to the dynamic changes in the plasma density of the corona.By observing the K corona,one can monitor the density disturbances due to the heating of the corona and/or the activity of the solar eruptions.It helps to understand the physical processes of coronal heating and solar eruption,also provides basic data for predicting the space weather events.Therefore,Observing the K corona has significance in both scientific and applicational aspects.This thesis aims to investigate the key technologies in detecting the K corona.We first simulate the brightness and polarization properties of the K corona based on the Thomson scattering principle,and then design the polarization measurement scheme of the K corona by using optics modeling.In this thesis,the K corona brightness distributions in the 4°-20°and 10°-60°fields of view and from multiple viewing angles are simulated.From the simulation,we found that the morphological characteristics of the K corona images relies on the observing angle,which is directly resulted from the density structures of the interplanetary solar wind.The results confirm that the brightness of the K corona rapidly decreases by more than 100 times from the inner edge to the outer edge of the field-of-view.The thesis also confirms that brightens structures rapidly expand while extending from near the sun toward the interplanetary space.Through the simulation of the polarization properties of K corona,the thesis found that the degree of polarization of K corona changes with the field of view.The trends are not monotonously increasing or decreasing,because the polarization is affected by the scattering angles.We also found that the polarization degree of K corona also depends on the viewing angle.Then,the design and parameter simulation of the polarization measurement device of K corona are carried out.The thesis found that the overall modulation efficiency of ferroelectric liquid crystal as the core device is better than that of the traditional design,by nearly three orders of magnitude.The study found that the use of dual ferroelectric liquid crystal polarization control can obtain K corona full polarization Stokes parameters through four shots.Finally,the dual ferroelectric liquid crystal device was optimized.we found that the optimized polarization measurement device could obtain Stokes parameters of I,Q and U through two modulations when one of the ferroelectric liquid crystals was replaced by a ?/4 wave plate.This increases the modulation efficiency by a factor of 2.Through the in-depth study of detection technologies,we achieve experiences for developing K corona detecting technologies,and also has some significance for the prospected solar ring mission that will observe the sun from multiple viewing angles simultaneously.