A Comprehensive Method of Estimating Electric Fields from Vector Magnetic Field and Doppler Measurements
Abstract
Photospheric electric fields, estimated from sequences of vector magnetic field and Doppler measurements, can be used to estimate the flux of magnetic energy (the Poynting flux) into the corona and as timedependent boundary conditions for dynamic models of the coronal magnetic field. We have modified and extended an existing method to estimate photospheric electric fields that combines a poloidaltoroidal decomposition (PTD) of the evolving magnetic field vector with Doppler and horizontal plasma velocities. Our current, more comprehensive method, which we dub the "PTDDopplerFLCT Ideal" (PDFI) technique, can now incorporate Doppler velocities from nonnormal viewing angles. It uses the FISHPACK software package to solve several twodimensional Poisson equations, a faster and more robust approach than our previous implementations. Here, we describe systematic, quantitative tests of the accuracy and robustness of the PDFI technique using synthetic data from anelastic MHD (ANMHD) simulations, which have been used in similar tests in the past. We find that the PDFI method has less than 1% error in the total Poynting flux and a 10% error in the helicity flux rate at a normal viewing angle (θ = 0) and less than 25% and 10% errors, respectively, at large viewing angles (θ < 60°). We compare our results with other inversion methods at zero viewing angle and find that our method's estimates of the fluxes of magnetic energy and helicity are comparable to or more accurate than other methods. We also discuss the limitations of the PDFI method and its uncertainties.
 Publication:

The Astrophysical Journal
 Pub Date:
 November 2014
 DOI:
 10.1088/0004637X/795/1/17
 arXiv:
 arXiv:1404.4027
 Bibcode:
 2014ApJ...795...17K
 Keywords:

 magnetic fields;
 Sun: evolution;
 Sun: flares;
 Sun: fundamental parameters;
 Sun: photosphere;
 sunspots;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 56 pages, 10 figures, ApJ (in press)