Statistical study of photospheric bright points in an active region and quiet Sun

The statistical properties of photospheric bright points (PBPs) in active regions (ARs) and the quiet Sun (QS) are investigated using two data sets obtained with the Dutch Open Telescope. Data for AR NOAA 10642 (July 12, 2004) and the QS (October 19, 2005) near the disk center are analyzed. For extracting PBPs, an automatic algorithm, employing Laplacian and morphological dilation (LMD) technique, is developed. The statistical properties of PBPs such as size distribution, contrast between maximum of PBPs and mean photospheric intensity, area coverage, number coverage and geometric shape are quantified. We then use goodness-of-fit to evaluate the fit of the size distribution of PBPs in the two regions. Finally, the Kolmogorov-Smirnov test is used to analyze the statistical difference in the AR and the QS. The following results are obtained: (1) the size distributions (probability density function) of PBPs in the two regions follow a lognormal distribution, moreover they are from the same size distribution; (2) the number coverage and the area coverage in the AR are about twice larger than those in the QS, respectively; (3) the geometrical shape of PBPs is quantified by the ratio of the length of major axis to the length of minor axis by the center of gravity. The ratio of about 50 % PBPs is less than 1.5, and their geometrical shapes are exactly alike in the two regions; (4) the ratio of maximum intensity of PBPs to their corresponding mean photospheric intensity is larger in the AR than in the QS. The results suggest that size and shape of PBPs in the AR and the QS are just the same, but the brightness of PBPs in the AR is different from that in the QS.

[1]  B. Bovelet,et al.  Dynamics of the solar active region finestructure , 2003 .

[2]  T. Ebisuzaki,et al.  Relationships between magnetic foot points and G-band bright structures , 2007, 0802.1765.

[3]  R. Schlichenmaier,et al.  Magnetic properties of G-band bright points in a sunspot moat , 2007, 0707.1232.

[4]  J. Hirzberger,et al.  Brightness and size of small-scale solar magnetic flux concentrations , 2004 .

[5]  T. Rimmele.  Plasma Flows Observed in Magnetic Flux Concentrations and Sunspot Fine Structure Using Adaptive Optics , 2004 .

[6]  R. Muller,et al.  The size distribution of magnetic bright points derived from Hinode/SOT observations , 2008, 0912.2637.

[7]  V. Abramenko,et al.  Distribution of the Magnetic Flux in Elements of the Magnetic Field in Active Regions , 2005 .

[8]  V. Yurchyshyn,et al.  STATISTICAL DISTRIBUTION OF SIZE AND LIFETIME OF BRIGHT POINTS OBSERVED WITH THE NEW SOLAR TELESCOPE , 2010, 1012.1584.

[9]  F. Giorgi,et al.  A Comparative Analysis of Photospheric Bright Points in an Active Region and in the Quiet Sun , 2012 .

[10]  D. Del Moro,et al.  IMAGING SPECTROPOLARIMETRY WITH IBIS: EVOLUTION OF BRIGHT POINTS IN THE QUIET SUN , 2009 .

[11]  Robert H. Hammerschlag,et al.  DOT tomography of the solar atmosphere. I. Telescope summary and program definition , 2004 .

[12]  Mats G. Lofdahl,et al.  Solar magnetic elements at 0".1 resolution. General appearance and magnetic structure , 2004 .

[13]  B. Bovelet,et al.  The quiet Sun's magnetic flux estimated from Ca II H bright inter-granular G-band structures , 2008, 1208.2160.

[14]  Peng-Yeng Yin,et al.  Pattern Recognition Techniques, Technology and Applications , 2008 .

[15]  P. J. Crockett,et al.  THE AREA DISTRIBUTION OF SOLAR MAGNETIC BRIGHT POINTS , 2010, 1009.2410.

[16]  Tenerife,et al.  MAGNETIC BRIGHT POINTS IN THE QUIET SUN , 2010, 1004.1885.

[17]  F. Berrilli,et al.  IMAGING SPECTROPOLARIMETRY WITH IBIS. II. ON THE FINE STRUCTURE OF G-BAND BRIGHT FEATURES , 2010, 1009.0721.

[18]  W. Cao,et al.  RESPONSE OF GRANULATION TO SMALL-SCALE BRIGHT FEATURES IN THE QUIET SUN , 2011, 1102.3404.

[19]  A. M. Title,et al.  New Observations of Subarcsecond Photospheric Bright Points , 1995 .

[20]  P. J. Crockett,et al.  Automated detection and tracking of solar magnetic bright points , 2009, 0905.3138.

[21]  J. Bonet,et al.  Bright Points in the Internetwork Quiet Sun , 2004, astro-ph/0405515.

[22]  B. Bovelet,et al.  Multiple-Scale Pattern Recognition Applied to Faint Intergranular G-band Structures , 2007 .

[23]  The size of penumbral fine structure , 2001 .