Stokes Line Parameters as Possible Indicators of Flaring Activity: A Comparison of Flaring and Non-Flaring Active Regions
Abstract
While the association between solar active regions (ARs) and solar flares is well-established, there is currently no reliable means of determining when (or if) a given AR will flare. Much of flare forecasting is based on the application of machine-learning statistical techniques that use parameters derived from the local magnetic field as predictors; these are commonly obtained through spectropolarimetric inversions using Stokes profiles from the observed radiation. The standard inversion codes, such as those based on the Milne-Eddington approximation, yield the average magnetic field values at or near flare locations. However, this fails to utilize the rich information contained in the shape of Stokes profiles, such as the existence of line-of-sight (LOS) magnetic and velocity gradients and multiple magnetic components along the LOS or within the resolving element. The resulting loss of information can potentially lead to inaccurate forecasts. We propose a novel approach, in which line parameters derived from spectrally-resolved Stokes profiles are considered as possible precursors to flare events. Using data from the spectropolarimeter onboard the Hinode satellite, we examine the amplitude asymmetry, net circular polarization, and degree of complexity of Stokes V profiles from several flaring and non-flaring ARs. Particular attention is given to regions near the polarity inversion line (PIL) due to its documented role in flare initiation. We define the PIL using the magnetic field vector relative to the solar surface, which we calculate from the Stokes Q, U, and V profiles; this corrects for projection effects arising from LOS observations of magnetic flux from ARs off disc center. In light of the shortcomings of existing methods, we hope to expand the set of viable indicators of flaring activity with the long-term goal of improving flare forecasting models.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSH31D3338R
- Keywords:
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- 7519 Flares;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY;
- 7524 Magnetic fields;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY;
- 7924 Forecasting;
- SPACE WEATHER;
- 7959 Models;
- SPACE WEATHER