Photospheric Magnetic Evolution in the WHI Active Regions

TL;DR

This study analyzes photospheric magnetic evolution in three active regions using magnetogram data to explore their relation to flares and CMEs, revealing limitations in current forecasting methods based solely on magnetic data.

Contribution

It introduces a comprehensive analysis of magnetic parameters across multiple scales in active regions and evaluates their effectiveness in predicting solar eruptions.

Findings

AR 10988 was expected to be most flare-productive but was not

AR 10989 produced similar flares and some CMEs as AR 10988

Current magnetic data-based forecasts have significant limitations

Abstract

Sequences of line-of-sight (LOS) magnetograms recorded by the Michelson-Doppler Imager are used to quantitatively characterize photospheric magnetic structure and evolution in three active regions that rotated across the Sun's disk during the Whole Heliosphere Interval (WHI), in an attempt to relate the photospheric magnetic properties of these active regions to flares and coronal mass ejections (CMEs). Several approaches are used in our analysis, on scales ranging from whole active regions, to magnetic features, to supergranular scales, and, finally, to individual pixels. We calculated several parameterizations of magnetic structure and evolution that have previously been associated with flare and CME activity, including total unsigned magnetic flux, magnetic flux near polarity inversion lines, amount of cancelled flux, the "proxy Poynting flux," and helicity flux. To catalog flare events, we used flare lists derived from both GOES and RHESSI observations. By most such measures, AR 10988 should have been the most flare- and CME-productive active region, and AR 10989 the least. Observations, however, were not consistent with this expectation: ARs 10988 and 10989 produced similar numbers of flares, and AR 10989 also produced a few CMEs. These results highlight present limitations of statistics-based flare and CME forecasting tools that rely upon line-of-sight photospheric magnetic data alone.