Journal ArticleDOI
A New Algorithm for Pattern Recognition and its Application to Granulation and Limb Faculae
Burkart Bovelet,E. Wiehr +1 more
TLDR
In this article, a new pattern recognition algorithm based on multiple intensity clips was developed, which assures an optimal adaptation to the solar structure under study, and is demonstrated by application to the intensity structure of solar granulation near the disk center, both speckle reconstructed and not.Abstract:
We have developed a new pattern-recognition algorithm based on multiple intensity clips which assures an optimal adaptation to the solar structure under study. The shapes found at higher clip levels are repeatedly extended to lower levels, thus filling more and more of the observed intensity contours. Additionally, at each intensity threshold new shapes, exceeding the level, are integrated. The number and height of the levels can be optimized making this `multiple level tracking' algorithm (MLT) superior to commonly used Fourier-based recognition techniques (FBR). The capability of MLT is demonstrated by application to the intensity structure of solar granulation near the disk center, both speckle reconstructed and not. Comparisons with Doppler maps prove its reliability. The granular pattern recognized by MLT differs essentially from that obtained with FBR. Elongated `snake-like' granules do not occur with MLT and, consequently, the perimeter-area distribution exhibits only a marginal `second branch' of higher fractal dimension, which dramatically diminishes the better the MLT pattern matches the granular structure. The final distribution obtained with optimized parameters has a single fractal dimension near 1.1, making the question of a `critical size', a `second branch', and the often discussed dimension of 4/3; highly questionable. This result is equally obtained from application of MLT to the corresponding Doppler velocity map of granular up-flows. In contrast, the pattern of down-flows contains some elongated `snake-like' structures with higher fractal dimension. We also use the new algorithm to recognize speckle-reconstructed limb faculae, which MLT separates from their granular surroundings, and compare both, granules and faculae, using large statistical samples. The facular grains near cosθ=57° exhibit a slightly different ellipticity than the (geometrically foreshortened) adjacent granules. However, small facular grains are more round than small granules and larger grains are more similar to granules.read more
Citations
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Journal ArticleDOI
25 Years of Self-Organized Criticality: Solar and Astrophysics
Markus J. Aschwanden,Norma Crosby,M. Dimitropoulou,Manolis K. Georgoulis,Stefan Hergarten,James McAteer,Alexander V. Milovanov,Alexander V. Milovanov,Alexander V. Milovanov,Shin Mineshige,Laura Morales,Naoto Nishizuka,Gunnar Pruessner,Raul Sanchez,A. Surja Sharma,Antoine Strugarek,Vadim M. Uritsky +16 more
TL;DR: In the following years, an inspiring cross-fertilization from complexity theory to solar and astrophysics took place, where the Self-Organized Criticality (SOC) concept was initially applied to solar flares, stellar flares, and magnetospheric substorms, and later extended to the radiation belt, the heliosphere, lunar craters, the asteroid belt and the Saturn ring, pulsar glitches, soft X-ray repeaters, blazars, blackhole objects, cosmic rays, and boson clouds as discussed by the authors.
Journal ArticleDOI
25 Years of Self-Organized Criticality: Solar and Astrophysics
Markus J. Aschwanden,Norma Crosby,M. Dimitropoulou,Manolis K. Georgoulis,Stefan Hergarten,James MdAteer,Alexander V. Milovanov,Shin Mineshige,Laura Morales,Naoto Nishizuka,Gunnar Pruessner,Raul Sanchez,Surja Sharma,Antoine Strugarek,Vadim M. Uritsky +14 more
TL;DR: In the following years, an inspiring cross-fertilization from complexity theory to solar and astrophysics took place, where the Self-Organized Criticality (SOC) concept was initially applied to solar flares, stellar flares, and magnetospheric substorms, and later extended to the radiation belt, the heliosphere, lunar craters, the asteroid belt and the Saturn ring, pulsar glitches, soft X-ray repeaters, blazars, blackhole objects, cosmic rays, and boson clouds as discussed by the authors.
Journal ArticleDOI
Statistics of Active Region Complexity: A Large-Scale Fractal Dimension Survey
TL;DR: In this paper, the magnetic complexity of active regions using a fractal dimension measure is quantified using full-disk MDI magnetograms of active region from a large data set (2742 days of the SOHO mission, 9342 active region images).
Journal ArticleDOI
Transverse Component of the Magnetic Field in the Solar Photosphere Observed by SUNRISE
Sanja Danilovic,B. Beeck,A. Pietarila,Manfred Schüssler,Sami K. Solanki,V. Martínez Pillet,J. A. Bonet,J. C. del Toro Iniesta,V. Domingo,Peter Barthol,Th. Berkefeld,Achim Gandorfer,Michael Knölker,Wolfgang Schmidt,A. M. Title +14 more
TL;DR: In this article, the first observations of the transverse component of a photospheric magnetic field acquired by the imaging magnetograph SUNRISE/IMaX were presented, and the authors obtained statistical properties of 4536 features with significant linear polarization signal.
Journal ArticleDOI
Image Processing Techniques and Feature Recognition in Solar Physics
TL;DR: This review presents a comprehensive and systematic overview of image-processing techniques used in automated feature-detection algorithms applied to solar data, such as visualization of solar imagery, cataloguing, statistics, theoretical modeling, prediction, and forecasting.
References
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Journal ArticleDOI
Statistical properties of solar granulation derived from the SOUP instrument on Spacelab 2
TL;DR: In this paper, computer algorithms and statistical techniques were used to identify, measure, and quantify the properties of solar granulation derived from movies collected by the Solar Optical Universal Polarimeter on Spacelab 2.
Journal ArticleDOI
Structure of the solar granulation.
Th. Roudier,R. Muller +1 more
TL;DR: In this paper, the structure of the solar granulation has been analyzed using computer-processed images of two very high resolution (0.25) white-light pictures obtained at the Pic-du-Midi Observatory.
Journal ArticleDOI
Time Series of Solar Granulation Images. I. Differences between Small and Large Granules in Quiet Regions
TL;DR: In this paper, a 90 minute time series of high spatial resolution white-light images of solar granulation, obtained at the Swedish Vacuum Solar Tower (Observatorio del Roque de los Muchachos, La Palma), was analyzed to study how the physical properties of the granules changed with size.
Journal ArticleDOI
Time Series of Solar Granulation Images. II. Evolution of Individual Granules
TL;DR: In this article, the properties of the evolution of solar granulation have been studied using an 80 minute time series of high-resolution white-light images obtained with the Swedish Vacuum Solar Telescope at the Observatorio del Roque de los Muchachos, La Palma.
Journal Article
Statistical Properties of Solar Granulation Derived from the Soup Instrument on Spacelab 2
TL;DR: In this paper, it was shown that the autocorrelation lifetime of granulation is a factor of two greater in magnetic field regions than in field-free quiet sun, and that exploding granules are a common feature of the granule evolution.
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