Three-dimensional Reconstruction Of The Escape Photons Of A Solar Hα Flare

Through the observational data which was transmitted back to the ground by space telescopes, we have seen many kinds of the three-dimensional structure of the active phenomena in solar atmosphere. As it well known, everything takes place in three-dimensional space and the simple two-dimensional simulation has lost some characteristics. But telescopes cannot lend us directly the information on the three-dimensional structure of the flare in opaque chromosphere and photosphere.Therefore we turn to reconstruct the three-dimensional structure based on theory of line formation which tells us that different lines are formed at different atmospheric layers and further, so do the different wavelength points. The contribution function for a line shows the contribution of different atmospheric levels to the emergent specific intensity. In the case of the emergent spectral intensity I_v, if it is regarded as the wavelength distribution of the photons escaping from solar atmosphere, the contribution function has been thought as the "probalility distribution" of these escape photons. Of course, the contribution function is also wavelength dependent, thus the escape photons with definite wavelength originate from different region. Redistributing the received photons of the observed area to the layers according to the corresponding contribution function and putting the photons together with different wavelength within a spectral line in each layer will result in the three-dimensional image. It is worthy noting that this process is quite different from constructing 3D image by locating 2D observational image of different lines to their formation depths respectively.The accuracy of three-dimensional image is decided by the contribution function, so is contribution function by the model of atmosphere. Thus obtaining the modelatmosphere is a key step. In this thesis, many sub-areas are plotted out in an Ha flare of selected durations by intensity contour. Within every sub-areas, we can get "quasi-profile" for each flaring point by the line center and the off-line-center observational data. By fitting the typical profile, we have obtained the model atmospheres for every sub-areas. Using the parameters of the model atmosphere, we can obtain contribution function exactly.Supervised by Prof. Qu and based on the line-center and off-line-center observations of 25cm refraction telescope of Big Bear Solar Observatory, we have reconstructed a series of the three-dimensional images of the escape photons. With the recovered model atmospheres, we make out the 2D temperature distribution. Combing the serial temperature distributions and the escape photon distributions, the evolvement of the flare is outlined.