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dc.contributor.advisor Büchner, Jörg Prof. Dr.
dc.contributor.author Widmer, Fabien
dc.date.accessioned 2016-08-31T08:06:39Z
dc.date.available 2016-08-31T08:06:39Z
dc.date.issued 2016-08-31
dc.identifier.uri http://hdl.handle.net/11858/00-1735-0000-0028-8820-4
dc.language.iso eng de
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subject.ddc 530 de
dc.title Magnetohydrodynamic Simulation of Reconnection in Turbulent Astrophysical Plasmas de
dc.type doctoralThesis de
dc.contributor.referee Büchner, Jörg Prof. Dr.
dc.date.examination 2016-07-19
dc.subject.gok Physik (PPN621336750) de
dc.description.abstracteng Turbulence is ubiquitous at large-Reynolds-number astrophysical plasmas like in the Solar corona. In such environments, the turbulence is thought to enhance the energy conversion rate by magnetic reconnection above the classical model predictions. Since turbulence cannot be simulated together with the large scale behaviour of the plasma, magnetic reconnection is studied through the average properties of turbulence. A Reynolds-averaged turbulence model is explored in which turbulence is self-sustained and -generated by the large scales (mean-) field inhomogeneities. Employing that model, the influence of turbulence is investigated by large-scale MHD numerical simulations solving evolution equations of the energy and cross-helicity of the turbulence together with the MHD equations. Magnetic reconnection is found to be either rapidly enhanced or suppressed by turbulence depending on the turbulence timescale. If the turbulence timescale is self-consistently calculated, reconnection is always strongly enhanced. Since the solar corona bears strong guide magnetic fields perpendicular to the reconnecting magnetic fields, the influences of a strong guide field on turbulent reconnection is separately investigated. A slow down of reconnection, obtained in the presence of a finite guide field, can be understood by a finite residual helicity working against the enhancement of reconnection by the turbulence. The influence of turbulence on magnetic reconnection is further studied by means of high resolution simulations of plasmoid-unstable current sheets. These simulations revealed the importance of turbulence for reaching fast reconnection. de
dc.contributor.coReferee Dreizler, Stefan Prof. Dr.
dc.contributor.thirdReferee Peter, Hardi Prof. Dr.
dc.contributor.thirdReferee Schmidt, Wolfram Pd Dr.
dc.contributor.thirdReferee Tilgner, Andreas Prof. Dr.
dc.contributor.thirdReferee Gizon, Laurent Prof. Dr.
dc.subject.eng Magnetic reconnection, Mean-field turbulence, Guide field, Subgrid-scale de
dc.identifier.urn urn:nbn:de:gbv:7-11858/00-1735-0000-0028-8820-4-5
dc.affiliation.institute Fakultät für Physik de
dc.identifier.ppn 869469622

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