We describe the PDFI_SS software library, which is designed to find the electric field at the Suns photosphere from a sequence of vector magnetogram and Doppler velocity measurements, and estimates of horizontal velocities obtained from local correlation tracking using the recently upgraded FLCT code. The library, a collection of Fortran subroutines, uses the PDFI technique described by Kazachenko et al. (2014), but modified for use in spherical, Plate-Carree geometry on a staggered grid. The domain over which solutions are found is a subset of the global spherical surface, defined by user-specified limits of colatitude and longitude. Our staggered-grid approach, based on that of Yee (1966), is more conservative and self-consistent compared to the centered, Cartesian grid used by Kazachenko et al. (2014). The library can be used to compute an end-to-end solution for electric fields from data taken by the HMI instrument aboard NASAs SDO Mission. This capability has been incorporated into the HMI pipeline processing system operating at SDOs JSOC. The library is written in a general and modular way so that the calculations can be customized to modify or delete electric field contributions, or used with other data sets. Other applications include nudging numerical models of the solar atmosphere to facilitate assimilative simulations. The library includes an ability to compute global (whole-Sun) electric field solutions. The library also includes an ability to compute Potential Magnetic Field solutions in spherical coordinates. This distribution includes a number of test programs which allow the user to test the software.
تحميل البحث