Electron Density Reconstruction of Solar Coronal Mass Ejections Based on Genetic Algorithm: Method and Application

We present a new method to reconstruct three dimensional density of Coronal Mass Ejection (CME) based on genetic algorithm (GA), namely genetic reconstruction method (GRM). At first, a model "CME" is constructed to produce synthetic CME images for the genetic reconstruction. Then the method is applied to coronagraph data from SOHO, STEREO-A and B on September 30th, 2013. In comparison with the existing methods for density reconstruction, GRM obtain global optimization of CME electron distribution. On the other hand, GRM decreases the difficulty of reconstruction by calculating electron number of every CME pixel in one of the view angles. Then the electrons are randomly redistributed along each line of sight (LOS) of CME pixel. Genetic operators named "crossover" and "mutation" are employed to optimize the electron distribution. Brightness of each pixel are recalculated through mechanism of Thomson scattering in multiple view angles. Genetic operator named "selection" is then employed to hold better distributions and eliminate the worse distributions according to fitness of recalculated brightness to the observed brightness. Such process may iterate through hundreds of times to obtain globally optimized electron distributions. We compare the reconstructed brightness with observation to show the availability of GRM. Results of GRM are also compared with those of polarimetric reconstruction and forward modeling for the method availability. We further apply the reconstructed CME into Space Weather Modeling Framework (SWMF) to obtain evolution of interplanetary CME and its geo-effectiveness. Time difference of the CME arrival between ACE measurement and SWMF simulation is less than 5 hours.