Systematic Errors and Uncertainties in the HMI Magnetic Data

Near-continuous, full-disk measurements of the Stokes I, Q, U and V profiles with a 40962 camera on-board HMI make possible the investigation of solar events in new and important ways. We summarize the uncertainties and systematic errors in the HMI vector and line-of-sight magnetic field data, including synoptic maps. Some of these were estimated prior to launch and others were unanticipated or newly determined. We showcase the NOAA AR 11944 and January 2014 HMI data to illustrate the magnitude of errors and the dependence on spacecraft parameters (especially orbital velocity) and solar physics conditions. We estimate the relative importance of the uncertainties and how these errors propagate through the models for space weather event analysis.