Discriminant analysis is a statistical approach for assigning a measurement to one of several mutually exclusive groups. Presented here is an application of the approach to solar flare forecasting, adapted to provide the probability that a measurement belongs to either group, the groups in this case being solar active regions which produced a flare within 24 hours and those that remained flare quiet. The technique is demonstrated for a large database of vector magnetic field measurements obtained by the University of Hawai?i Imaging Vector Magnetograph. For a large combination of variables characterizing the photospheric magnetic field, the results are compared to a Bayesian approach for solar flare prediction, and to the method employed by the U.S. Space Environment Center (SEC). Although quantitative comparison is difficult as the present application provides active region (rather than whole-Sun) forecasts, and the
present database covers only part of one solar cycle, the performance of the method appears comparable to
the other approaches.
Authors: G. Barnes, K.D. Leka, E.A. Schumer and D.J. Della-Rose
Publication Status: published
Last Modified: 2007-09-07 10:19
Photospheric Magnetic Field Properties of Flaring Versus Flare-Quiet Active Regions. III. Magnetic Charge Topology Models
A Magnetic Charge Topology (MCT) model is applied to time series of photospheric vector magnetic field data for seven active regions divided into epochs classified as flare-quiet and flare-productive. In an approach which parallels an earlier study by the authors using quantities describing the photospheric properties of the vector magnetic field, we define quantities derived from the MCT analysis that quantify the complexity and topology of the active region coronal fields. With the goal of distinguishing between flare-quiet and flare-imminent magnetic topology, the time series are initially displayed for three active regions for visual inspection with few clear distinguishing characteristics resulting. However, an analysis of all twenty-four epochs using the Discriminant Analysis statistical approach indicates that coronal field topology, derived from observed photospheric vertical field, may indeed hold relevant information for distinguishing these populations, although the small sample size precludes a definite conclusion. The variables derived from the characterization of coronal topology routinely result in higher probabilities of being able to distinguish between the two populations than the analogous variables derived for the photospheric field.
Authors: G. Barnes and K.D. Leka
Publication Status: ApJ (in press)
Last Modified: 2006-06-14 11:23
Implementing a Magnetic Charge Topology Model for Solar Active Regions
Information about the magnetic topology of the solar corona is crucial to understanding solar energetic events. One approach to characterizing the topology which has had some success is Magnetic Charge Topology, in which the topology is defined by partitioning the observed photospheric field into a set of discrete sources and determining which pairs are interlinked by coronal field lines. The level of topological activity is then quantified through the transfer of flux between regions of differing field line connectivity. We discuss in detail how to implement such a model for a time series of vector magnetograms, paying particular attention to distinguishing real evolution of
the photospheric magnetic flux from changes due to variations in atmospheric seeing, as well as uncorrelated noise. We determine the reliability of our method and estimate the uncertainties in its results. We then demonstrate it through an application to NOAA active region 8210, which has been the subject of extensive previous study.
Authors: G. Barnes, D.W. Longcope & K.D. Leka
Publication Status: ApJ (accepted)
Last Modified: 2005-04-22 13:18