A fast technique for improved 3-dimensional mapping of the solar corona

To obtain improved maps of the coronal electron density distribution, an iterative technique has been devised in which an approximation of the unknown distribution is successively modified to reduce discrepancies with the original data. With this technique, the corona can now be mapped to a much finer resolution than shown in the previous papers without greatly increasing the computational cost. The series representation of density may now contain >23,000 terms compared with the previous limit of 128. This results in a fourfold increase in linear resolution, so that features about a tenth of a solar radius in width are now separated. The iteration algorithm can be adjusted to apply a mathematically optimal correction to a given approximation of the density. Although this correction minimizes noise levels, a cheaper version of the algorithm yields a better result.