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

Dimitropoulou, M; Georgoulis, M; Isliker, H; Vlahos, L; Anastasiadis, A; Strintzi, D; Moussas, X

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