Bingert, Sven

[["dc.bibliographiccitation.artnumber","A30"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","550"],["dc.contributor.author","Bingert, Sven"],["dc.contributor.author","Hardi, Peter"],["dc.date.accessioned","2019-12-13T08:29:03Z"],["dc.date.available","2019-12-13T08:29:03Z"],["dc.date.issued","2012"],["dc.description.abstract","Context. We investigate the statistics of the spatial and temporal distribution of the coronal heating in a three-dimensional magneto- hydrodynamical (3D MHD) model. The model describes the temporal evolution of the corona above an observed active region. The model is driven by photospheric granular motions which braid the magnetic field lines. This induces currents and their dissipation heats the plasma. We evaluate the transient heating as subsequent heating events and analyze their statistics. The results are then interpreted in the context of observed flare statistics and coronal heating mechanisms. Methods. To conduct the numerical experiment we use a high order finite difference code which solves the partial differential equations for the conservation of mass, the momentum and energy balance, and the induction equation. The energy balance includes the Spitzer heat conduction and the optical thin radiative loss in the corona. Results. The temporal and spatial distribution of the Ohmic heating in the 3D MHD model follow a power law and can therefore be explained by system in a self-organized critical state. The slopes of the power law are similar to the results based on flare observations. We find that the corona is heated foot point dominated and the coronal heating is dominated by events called nanoflares with energies on the order of 1017 J."],["dc.identifier.arxiv","1211.6417v2"],["dc.identifier.doi","10.1051/0004-6361/201220469"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/62749"],["dc.language.iso","en"],["dc.relation.issn","0004-6361"],["dc.relation.issn","1432-0746"],["dc.title","Nanoflare statistics in an active region 3D MHD coronal model"],["dc.type","journal_article"],["dc.type.internalPublication","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","A86"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","589"],["dc.contributor.author","Bourdin, Philippe-A."],["dc.contributor.author","Bingert, Sven"],["dc.contributor.author","Hardi, Peter"],["dc.date.accessioned","2019-12-13T08:11:40Z"],["dc.date.available","2019-12-13T08:11:40Z"],["dc.date.issued","2016"],["dc.description.abstract","Context. The structure and heating of coronal loops are investigated since decades. Established scaling laws relate fundamental quantities like the loop apex temperature, pressure, length, and the coronal heating. Aims. We test such scaling laws against a large-scale 3D MHD model of the Solar corona, which became feasible with nowadays high-performance computing. Methods. We drive an active region simulation a with photospheric observations and found strong similarities to the observed coronal loops in X-rays and EUV wavelength. A 3D reconstruction of stereoscopic observations showed that our model loops have a realistic spatial structure. We compare scaling laws to our model data extracted along an ensemble of field lines. Finally, we fit a new scaling law that represents well hot loops and also cooler structures, which was not possible before only based on observations. Results. Our model data gives some support for scaling laws that were established for hot and EUV-emissive coronal loops. For the RTV scaling law we find an offset to our model data, which can be explained by 1D considerations of a static loop with a constant heat input and conduction. With a fit to our model data we set up a new scaling law for the coronal heat input along magnetic field lines. Conclusions. RTV-like scaling laws were fitted to hot loops and therefore do not predict well the coronal heat input for cooler structures that are hardly observable. The basic differences between 1D and self-consistent 3D modeling account for deviations between our and earlier scaling laws. We also conclude that a heating mechanism by MHD-turbulent dissipation within a braided flux tube would heat the corona stronger than consistent with our model corona."],["dc.identifier.arxiv","1603.05276v2"],["dc.identifier.doi","10.1051/0004-6361/201525840"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/62744"],["dc.language.iso","en"],["dc.relation.issn","0004-6361"],["dc.relation.issn","1432-0746"],["dc.title","Scaling laws of coronal loops compared to a 3D MHD model of an Active Region"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","113"],["dc.bibliographiccitation.lastpage","120"],["dc.bibliographiccitation.volumetitle","High Performance Computing in Science and Engineering ‘14"],["dc.contributor.author","Bingert, Sven"],["dc.contributor.author","Hardi, Peter"],["dc.contributor.editor","Nagel, W."],["dc.contributor.editor","Kröner, D."],["dc.contributor.editor","Resch, M."],["dc.date.accessioned","2019-12-13T08:21:57Z"],["dc.date.available","2019-12-13T08:21:57Z"],["dc.date.issued","2015"],["dc.description.abstract","We employ a three dimensional magneto-hydrodynamical (3D MHD) model to investigate the statistics of the spatial and temporal distribution of the coronal heating. The model describes the evolution of the solar corona above an observed Active Region. This model is additionally compared to coronal models where the underlying photospheric magnetic field consists of simplified magnetic configurations. In all models random like photospheric motions braid the magnetic field. This induces currents in the upper atmosphere eventually leading to coronal heating by their dissipation. We analyze the heating process which is in general transient in time and space. We compare the results to observed flare statistics."],["dc.identifier.doi","10.1007/978-3-319-10810-0_8"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/62747"],["dc.language.iso","de"],["dc.publisher","Springer"],["dc.publisher.place","Cham"],["dc.relation.doi","10.1007/978-3-319-10810-0"],["dc.relation.isbn","978-3-319-10809-4"],["dc.relation.isbn","978-3-319-10810-0"],["dc.relation.ispartof","High Performance Computing in Science and Engineering ‘14"],["dc.title","Nanoflare Heating in the Solar Corona"],["dc.type","book_chapter"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A112"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","530"],["dc.contributor.author","Bingert, Sven"],["dc.contributor.author","Hardi, Peter"],["dc.date.accessioned","2019-12-13T08:36:37Z"],["dc.date.available","2019-12-13T08:36:37Z"],["dc.date.issued","2011"],["dc.description.abstract","We investigate the spatial and temporal evolution of the heating of the corona of a cool star such as our Sun in a three-dimensional magneto-hydrodynamic (3D MHD) model. We solve the 3D MHD problem numerically in a box representing part of the (solar) corona. The energy balance includes Spitzer heat conduction along the magnetic field and optically thin radiative losses. The self-consistent heating mechanism is based on the braiding of magnetic field lines rooted in the convective photosphere. Magnetic stress induced by photospheric motions leads to currents in the atmosphere which heat the corona through Ohmic dissipation. While the horizontally averaged quantities, such as heating rate, temperature or density, are relatively constant in time, the simulated corona is highly variable and dynamic, on average reaching temperatures and densities as found in observations. The strongest heating per particle is found in the transition region from the chromosphere to the corona. The heating is concentrated in current sheets roughly aligned with the magnetic field and is transient in time and space. This supports the idea that numerous small heating events heat the corona, often referred to a nanoflares."],["dc.identifier.arxiv","1103.6042v2"],["dc.identifier.doi","10.1051/0004-6361/201016019"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/62752"],["dc.language.iso","en"],["dc.relation.issn","0004-6361"],["dc.relation.issn","1432-0746"],["dc.title","Intermittent heating in the solar corona employing a 3D MHD model"],["dc.type","journal_article"],["dc.type.internalPublication","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A97"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","531"],["dc.contributor.author","Zacharias, Pia"],["dc.contributor.author","Bingert, Sven"],["dc.contributor.author","Hardi, Peter"],["dc.date.accessioned","2019-12-13T08:38:53Z"],["dc.date.available","2019-12-13T08:38:53Z"],["dc.date.issued","2011"],["dc.description.abstract","The origin of solar transition region redshifts is not completely understood. Current research is addressing this issue by investigating three-dimensional magneto-hydrodynamic models that extend from the photosphere to the corona. By studying the average properties of emission line profiles synthesized from the simulation runs and comparing them to observations with present-day instrumentation, we investigate the origin of mass flows in the solar transition region and corona. Doppler shifts were determined from the emission line profiles of various extreme-ultraviolet emission lines formed in the range of =10^4-10^6$ K. Plasma velocities and mass flows were investigated for their contribution to the observed Doppler shifts in the model. In particular, the temporal evolution of plasma flows along the magnetic field lines was analyzed. Comparing observed vs. modeled Doppler shifts shows a good correlation in the temperature range $\\log(T$/[K])=4.5-5.7, which is the basis of our search for the origin of the line shifts. The vertical velocity obtained when weighting the velocity by the density squared is shown to be almost identical to the corresponding Doppler shift. Therefore, a direct comparison between Doppler shifts and the model parameters is allowed. A simple interpretation of Doppler shifts in terms of mass flux leads to overestimating the mass flux. Upflows in the model appear in the form of cool pockets of gas that heat up slowly as they rise. Their low temperature means that these pockets are not observed as blueshifts in the transition region and coronal lines. For a set of magnetic field lines, two different flow phases could be identified. The coronal part of the field line is intermittently connected to subjacent layers of either strong or weak heating, leading either to mass flows into the loop or to the draining of the loop."],["dc.identifier.arxiv","1105.5491v1"],["dc.identifier.doi","10.1051/0004-6361/201016047"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/62753"],["dc.language.iso","en"],["dc.relation.issn","0004-6361"],["dc.relation.issn","1432-0746"],["dc.title","Investigation of mass flows in the transition region and corona in a three-dimensional numerical model approach"],["dc.type","journal_article"],["dc.type.internalPublication","no"],["dspace.entity.type","Publication"]]