Spatio-temporal analysis and forward modeling of solar polar plumes in white light

摘要

The analysis of the data provided by the LASCO/C2 coronagraph on board the SOHO spatial observatory revealed the fractal characteristics of many remarkable structures of the solar corona forming the solar atmosphere. A multiscale analysis of recent image sequences has brought a clearer view of the evolution and the local structure of these features which results from a two steps projection process of the 2D electron distribution over the Sun polar caps. To get an insight in the volume density distribution over these caps and their evolution within time, we used the forward modeling approach based on the present knowledge about the plasma distribution, the physical process of diffusion and the projection geometry on the field of view. The analysis provides us with the multifractal characterization of the observed phenomena. In the forward modeling process the goal is to reconstruct the time sequence of 2D electronic distributions slowly evolving over the Sun polar caps. We used different methodologies: the inverse Fourier transform of 2D+1D (surface and time) frequency modeling, the evolving multiscale synthesis with Gaussian wavelets and the concealed Markov approach. Finaly, a procedure derived from the Voss generation scheme of fBm (fractal Brownian motion) fractals has been successfully developped. These different methods are compared and their relative advantages and drawbacks discussed.