Statistical techniques for the detection and analysis of solar explosive events

Abstract

Context. Solar explosive events are commonly explained as small-scale magnetic reconnection events, although an unambiguous confirmation of this scenario remains elusive owing to the lack of spatial resolution and the statistical analysis of sufficiently large samples of this type of events. Aims. We propose a sound statistical treatment of data cubes consisting of a temporal sequence of long-slit spectra of the solar atmosphere. The analysis comprises all stages from the explosive event detection to its characterization and the subsequent sample study. Methods. We designed two complementary approaches based on the combination of standard statistical techniques (the robust principal component analysis in one approach and wavelet decomposition and independent component analysis in the second) to obtain least biased samples. These techniques are implemented in the spirit of letting the data speak for themselves. The analysis is carried out for two spectral lines: the C iv line at 1548.2 Å and the Ne viii line at 770.4 Å. Results. We find significant differences between the characteristics of the line profiles emitted in the proximities of two active regions, and in the quiet Sun, most visible in the relative importance of a separate population of red shifted profiles. We also find a higher frequency of explosive events near the active regions, and in the C iv line. The distribution of the explosive events characteristics is interpreted in the light of recent numerical simulations. Finally, we point out several regions of the parameter space where the reconnection model has to be refined in order to explain the observations.

Comparative Analysis of a Transition Region Bright Point with a Blinker and Coronal Bright Point Using Multiple EIS Emission Lines

“…The blinker was selected at 16:49:18 UT in the O v λ192.900Å (log T = 5.4) emission line. After each event was selected their heliographic solar coordinates were then tracked throughout the EIS observation sequence by accounting for solar rotation (≈ 0.17 arcsec min −1 ) and instrument pointing (Sarro and Berihuete, 2011). …”

Temporal Pointing Variations of the Solar Dynamics Observatory’s HMI and AIA Instruments on Subweekly Time Scales

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A Multi-wavelength Analysis of Active Regions and Sunspots by Comparison of Automatic Detection Algorithms

“…PCA has been used previously for various purposes in solar-physics and space-weather literature, e.g. to detect outliers (Sarro and Berihuete, 2011), to reduce dimensionality (Dudok de Wit and Auchère, 2007), or for exploratory data analysis of space-weather data sets (Habash Krause, Franz, and Stevenson, 2011).…”