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The correlation of fractal structures in the photospheric and the coronal magnetic field

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dc.contributor.author Dimitropoulou, M en
dc.contributor.author Georgoulis, M en
dc.contributor.author Isliker, H en
dc.contributor.author Vlahos, L en
dc.contributor.author Anastasiadis, A en
dc.contributor.author Strintzi, D en
dc.contributor.author Moussas, X en
dc.date.accessioned 2014-03-01T01:32:03Z
dc.date.available 2014-03-01T01:32:03Z
dc.date.issued 2009 en
dc.identifier.issn 0004-6361 en
dc.identifier.uri https://dspace.lib.ntua.gr/xmlui/handle/123456789/20041
dc.subject Sun: corona en
dc.subject Sun: flares en
dc.subject Sun: photosphere en
dc.subject.classification Astronomy & Astrophysics en
dc.subject.other Coronal magnetic fields en
dc.subject.other Coronal structure en
dc.subject.other Extrapolation methods en
dc.subject.other Force free fields en
dc.subject.other Fractal properties en
dc.subject.other Fractal structures en
dc.subject.other Lower limits en
dc.subject.other Magnetic features en
dc.subject.other Magnetic patterns en
dc.subject.other Nonlinear force en
dc.subject.other Photospheric magnetic field en
dc.subject.other Second level en
dc.subject.other Sun: corona en
dc.subject.other Sun: flares en
dc.subject.other Sun: photosphere en
dc.subject.other Vector magnetograms en
dc.subject.other Approximation theory en
dc.subject.other Correlation methods en
dc.subject.other Extrapolation en
dc.subject.other Fractal dimension en
dc.subject.other Magnetic fields en
dc.subject.other Solar energy en
dc.subject.other Sun en
dc.subject.other Three dimensional en
dc.subject.other Magnetic materials en
dc.title The correlation of fractal structures in the photospheric and the coronal magnetic field en
heal.type journalArticle en
heal.identifier.primary 10.1051/0004-6361/200911852 en
heal.identifier.secondary http://dx.doi.org/10.1051/0004-6361/200911852 en
heal.language English en
heal.publicationDate 2009 en
heal.abstract Context. This work examines the relation between the fractal properties of the photospheric magnetic patterns and those of the coronal magnetic fields in solar active regions.Aims. We investigate whether there is any correlation between the fractal dimensions of the photospheric structures and the magnetic discontinuities formed in the corona.Methods. To investigate the connection between the photospheric and coronal complexity, we used a nonlinear force-free extrapolation method that reconstructs the 3d magnetic fields using 2d observed vector magnetograms as boundary conditions. We then located the magnetic discontinuities, which are considered as spatial proxies of reconnection-related instabilities. These discontinuities form well-defined volumes, called here unstable volumes. We calculated the fractal dimensions of these unstable volumes and compared them to the fractal dimensions of the boundary vector magnetograms.Results. Our results show no correlation between the fractal dimensions of the observed 2d photospheric structures and the extrapolated unstable volumes in the corona, when nonlinear force-free extrapolation is used. This result is independent of efforts to (1) bring the photospheric magnetic fields closer to a nonlinear force-free equilibrium and (2) omit the lower part of the modeled magnetic field volume that is almost completely filled by unstable volumes. A significant correlation between the fractal dimensions of the photospheric and coronal magnetic features is only observed at the zero level (lower limit) of approximation of a current-free (potential) magnetic field extrapolation.Conclusions. We conclude that the complicated transition from photospheric non-force-free fields to coronal force-free ones hampers any direct correlation between the fractal dimensions of the 2d photospheric patterns and their 3d counterparts in the corona at the nonlinear force-free limit, which can be considered as a second level of approximation in this study. Correspondingly, in the zero and first levels of approximation, namely, the potential and linear force-free extrapolation, respectively, we reveal a significant correlation between the fractal dimensions of the photospheric and coronal structures, which can be attributed to the lack of electric currents or to their purely field-aligned orientation. © 2009 ESO. en
heal.publisher EDP SCIENCES S A en
heal.journalName Astronomy and Astrophysics en
dc.identifier.doi 10.1051/0004-6361/200911852 en
dc.identifier.isi ISI:000270907100027 en
dc.identifier.volume 505 en
dc.identifier.issue 3 en
dc.identifier.spage 1245 en
dc.identifier.epage 1253 en


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