The PDFI_SS Electric Field Inversion Software
Abstract
We describe the PDFI_SS software library, which is designed to find the electric field at the Sun's 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 Fourier Local Correlation Tracking code. The library, a collection of FORTRAN subroutines, uses the "PDFI" technique described by Kazachenko et al., but modified for use in spherical, Plate Carrée geometry on a staggered grid. The domain over which solutions are found is a subset of the global spherical surface, defined by userspecified limits of colatitude and longitude. Our staggered grid approach, based on that of Yee, is more conservative and selfconsistent compared to the centered, Cartesian grid used by Kazachenko et al. The library can be used to compute an endtoend solution for electric fields from data taken by the HMI instrument aboard NASA's SDO mission. This capability has been incorporated into the HMI pipeline processing system operating at SDO's Joint Science Operations Center. 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" (wholeSun) 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 that allow the user to test the software.
 Publication:

The Astrophysical Journal Supplement Series
 Pub Date:
 May 2020
 DOI:
 10.3847/15384365/ab8303
 arXiv:
 arXiv:1912.08301
 Bibcode:
 2020ApJS..248....2F
 Keywords:

 Solar magnetic fields;
 Solar active region magnetic fields;
 Active solar corona;
 Solar photosphere;
 Space weather;
 Solar activity;
 Theoretical techniques;
 Magnetohydrodynamical simulations;
 1503;
 1975;
 1988;
 1518;
 2037;
 1475;
 2093;
 1966;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 68 pages, 28 figures, 3 tables. This version (arXiv) will be updated when major changes to the software occur