About
56
Publications
6,044
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
943
Citations
Introduction
Skills and Expertise
Additional affiliations
January 2010 - December 2013
December 2003 - December 2009
Publications
Publications (56)
The concept of FAIR Digital Objects represents a foundational step towards realizing machine-actionable, interoperable data infrastructures across scientific and industrial domains. As digital spaces become increasingly heterogeneous, scalable mechanisms for data processing and interpretability are essential. This paper provides a comparative analy...
A project has beenstarted to create a distributed testbed based on FDOs and using the DOIP protocol. This paper describes the intentions and the required components to build such a testbed. It can beseen as a first step towards an international FDO testbed.
The FDO Manager is a free and open source reference implementation of basic FDO Operations like retrieve, create or update. It is based on the Digital Object Architecture and realizes an FDO architecture employing persistent identifiers that can be resolved via the Digital Object Identifier Resolution Protocol.
The FDO One project aims at building a global integrated dataspace based on FAIR digital objects (FDOs). The project's main contributions are the development of a publicly accessible FDO infrastructure, an international FDO testbed and bridges between multiple emerging dataspaces. These dataspaces are defined by important industrial standards, such...
The FAIR principles have become the gold standard for best practice in research data management. The acronym FAIR stands for Findable, Accessible, Interoperable, and Reusable. To guarantee the reusability of digital objects, it is essential to ensure that not only the object itself, but also its associated metadata, is accompanied by comprehensive...
Graph database has developed rapidly and plays an important role in research nowadays. It helps scientists in various ways, e.g., finding related works, exploring works in a research area, or gaining knowledge from connections between different nodes. There are already some graph databases for research available on the Internet. However, they do no...
This paper introduces a newly developed service called MINE. The service assists Digital Humanities scientists in solving two problems: data acquisition and text analysis on a large scale. MINE consists of two main components: a search engine and a workspace. The search engine does not only provide a way to search across various data sources, but a...
This paper introduces the MINE platform, which aims to help scientists overcome the difficulties in data acquisition and text analysis in a large scale. Foremost, MINE provides a search portal, which facilitates the data acquisition process by allowing users to search and download data across multiple repositories. After investigating other state-o...
The paper gives a brief introduction about the workflow management platform, Flowable, and how it is used for textual-data management. It is relatively new with its first release on 13 October, 2016. Despite the short time on the market, it seems to be quickly well-noticed with 4.6 thousand stars on GitHub at the moment. The focus of our project is...
COST (European Cooperation in Science and Technology) is a funding organisation for research and innovation networks. One of the objectives of the COSTAction called “Mobilising Data, Policies and Experts in Scientific Collections“ (MOBILISE) is to work on documents for expert training with broad involvement of professionals from the participating E...
The demand for processing power by modern data analyses is continuously increasing. High-Performance-Computing (HPC) resources can help but the standard process is for users to log in to use the HPC systems which is often complicated and not well suited for the integration in workflows. In order to bridge the gap between external workflow tools and...
The Pencil Code is a highly modular physics-oriented simulation code that can be adapted to a wide range of applications. It is primarily designed to solve partial differential equations (PDEs) of compressible hydrodynamics and has lots of add-ons ranging from astrophysical magnetohydrodynamics (MHD) to meteorological cloud microphysics and enginee...
The hot loop structures in the solar corona can be well modelled by three-dimensional magnetohydrodynamic simulations, where the corona is heated by field line braiding driven at the photosphere. To be able to reproduce the emission comparable to observations, one has to use realistic values for the Spitzer heat conductivity, which puts a large con...
The Handle Software manages references to resources of information. However, it does not support a search functionality. A prior implementation with Elasticsearch could not efficiently capture the complex structure of our dataset, especially the relationships between handles. In this paper, we apply a graph database together with Elasticsearch to p...
The hot loop structures in the solar corona can be well modeled by three dimensional magnetohydrodynamic simulations, where the corona is heated by field line braiding driven at the photosphere. To be able to reproduced the emission comparable to observations, one has to use realistic values for the Spitzer heat conductivity, which puts a large con...
Zusammenfassung
Durch die Zunahme an digitalen Forschungsmethoden in den Geisteswissenschaften nimmt auch die Nachfrage nach Diensten zum Forschungsdatenmanagement rasant zu. Wir beschreiben die sich daraus ergebenden Herausforderungen und Perspektiven eines geisteswissenschaftlichen Datenzentrums zur nachhaltigen Sicherung und Bereitstellung digit...
Aims. We study the magnetic field and current structure associated with a coronal loop. Through this we investigate to what extent the assumptions of a force-free magnetic field break down and where they might be justified. Methods. We analyze a three-dimensional (3D) magnetohydrodynamic (MHD) model of the solar corona in an emerging active region...
The project poster shows an overview of our project, i.e., the different work packages. In addition, we show current work, first results and describe our goal.
Research data is – regardless its disciplinary provenance – very heterogeneous in terms of data formats, applied research methods and content. In contrast to publications, a much broader spectrum of data representations has to be considered by research data infrastructures. Within the Humanities Data Centre project (HDC) an initial service portfoli...
The HDC Application Preservation – a Service for Archiving and Providing Complex Research Results. Research data today becomes more and more complex, moving away from file-based structures and content to more and more complex representations of data. These complex representations of research data usually convey a more complete picture of a research...
We study the magnetic field and current structure associated with a coronal loop. Through this we investigate to what extent the assumptions of a force-free magnetic field break down. We analyse a three-dimensional MHD model of the solar corona in an emerging active region with the focus on the structure of the forming coronal loops. The lower boun...
Complex software environments, like virtual research environments or visualisation frameworks, are increasingly used to conduct research and present its results. While there is a growing amount for solutions facilitating the (granular) citation of publications and research data, the citation of complex software environments remains a challenge. Thi...
Context. The structure and heating of coronal loops have been investigated for decades. Established scaling laws relate fundamental quantities like the loop apex temperature, pressure, length, and coronal heating.
Aims. We test these scaling laws against a large-scale 3D magneto-hydrodynamics (MHD) model of the solar corona, which became feasible w...
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-perform...
Context. We have conducted a 3D MHD simulation of the solar corona above an active region in full scale and high resolution, which shows coronal loops, and plasma flows within them, similar to observations.
Aims. We want to find the connection between the photospheric energy input by field-line braiding with the coronal energy conversion by Ohmic d...
The outer solar atmosphere, the corona, contains plasma at temperatures of
more than a million K, more than 100 times hotter that solar surface. How this
gas is heated is a fundamental question tightly interwoven with the structure
of the magnetic field in the upper atmosphere. Conducting numerical experiments
based on magnetohydrodynamics we accou...
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 fie...
We conducted a high-resolution numerical simulation of the solar corona above a stable active region. The aim is to test the
field line braiding mechanism for a sufficient coronal energy input. We also check the applicability of scaling laws for coronal
loop properties like the temperature and density. Our 3D MHD model is driven from below by Hinod...
Interna(onal collabora(on to provide PIDs for the research community ! Use of a commonly agreed process for the alloca(on, management and resolu(on of PIDs ! So=ware uses the Handle system (www.handle.net) ! Provides a global service of the handle system ! Close coopera(on with the RDA PIT working group ! Standardiza(on of the policies ! Represen(n...
We present the first model that couples the formation of the corona of a
solar active region to a model of the emergence of a sunspot pair. This allows
us to study when, where, and why active region loops form, and how they evolve.
We use a 3D radiation MHD simulation of the emergence of an active region
through the upper convection zone and the ph...
Parameter and setup files used for a 3D-MHD simulation with the Pencil Code. The parameters are needed to reproduce the simulation, while the setup files show which modules of the Pencil Code were used to conduct the simulation.
The parameters file are in the state as used at the end of the simulation, when the analysis was performed. With the log...
We will use new data from the High-resolution Coronal Imager (Hi-C) with
unprecedented spatial resolution of the solar corona to investigate the
structure of coronal loops down to 0.2 arcsec. During a rocket flight Hi-C
provided images of the solar corona in a wavelength band around 193 A that is
dominated by emission from Fe XII showing plasma at...
Aims. The goal is to employ a 3D magnetohydro dynamics (MHD) model including spectral synthesis to model the corona in an observed solar active region. This will allow us to judge the merits of the coronal heating mechanism built into the 3D model.
Methods. Photospheric observations of the magnetic field and horizontal velocities in an active regio...
We investigate the difference in the spatial distribution of the energy input
for parametrizations of different mechanisms to heat the corona of the Sun and
possible impacts on the coronal emission. We use a 3D MHD model of a solar
active region as a reference and compare the Ohmic-type heating in this model
to parametrizations for alternating curr...
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. Thi...
The corona of the Sun is dominated by emission from loop-like structures.
When observed in X-ray or extreme ultraviolet emission, these million K hot
coronal loops show a more or less constant cross section. In this study we show
how the interplay of heating, radiative cooling, and heat conduction in an
expanding magnetic structure can explain the...
Condensations in the more than 10^6 K hot corona of the Sun are commonly
observed in the extreme ultraviolet (EUV). While their contribution to the
total solar EUV radiation is still a matter of debate, these condensations
certainly provide a valuable tool for studying the dynamic response of the
corona to the heating processes. We investigate diff...
We investigate the processes that lead to the formation, ejection and fall of
a confined plasma ejection that was observed in a numerical experiment of the
solar corona. By quantifying physical parameters such as mass, velocity, and
orientation of the plasma ejection relative to the magnetic field, we provide a
description of the nature of this par...
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...
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...
We present data from Hinode/EIS, compare these to 3D MHD coronal models and outline forward models using SDO data. EUV lines originating in an active region show asymmetric line profiles that are interpreted using multi-Gaussian line fitting. Depending of the structure, a minor component can show high upflow speeds of above 100 km/S or it can be su...
The structure and dynamics of a box in a stellar corona can be modeled employing a 3D MHD model for different levels of magnetic activity. Depending on the magnetic flux through the surface the nature of the resulting coronal structures can be quite different. We investigate a model of an active region for two sunspots surrounded by magnetic field...
We study extreme-ultraviolet emission line spectra derived from three-dimensional magnetohydrodynamic models of structures in the corona. In order to investigate the effects of increased magnetic activity at photospheric levels in a numerical experiment, a much higher magnetic flux density is applied at the photosphere as compared to the Sun. Thus,...
We study extreme-ultraviolet emission line spectra derived from three-dimensional magnetohydrodynamic models of structures in the corona. In order to investigate the effects of increased magnetic activity at photospheric levels in a numerical experiment, a much higher magnetic flux density is applied at photospheric levels as compared to the Sun. T...
Emission lines in the transition region and corona show persistent line shifts. It is a major challenge to understand the dynamics in the upper atmosphere and thus these line shifts, which are a signature of the mass cycle between the chromosphere and the corona. We examine EUV emission line profiles synthesized from a 3D MHD coronal model of a sol...
Observations of the solar corona show loop-like structures formed by plasma at temperatures of one million degrees and higher. Since the solar surface is much cooler than the corona, a heating mechanism must be responsible for the high temperatures. The dissipation of magnetic fields in the corona could provide such a heating mechanism. However, th...
We study EUV emission line spectra derived from 3D MHD models of structures in the corona, in particular of an active region surrounded by a strong chromospheric network. The 3D MHD models account properly for the energy balance, especially for heat conduction and radiative losses. This allows us to reliably synthesize the profiles of EUV emission...
The structure and dynamics of a box in a stellar corona can be modeled
employing a 3D MHD model for different levels of magnetic activity. In
these models we account for the mass, momentum and energy balance
including heat conduction and radiative losses. The heating is through
current dissipation in the corona driven by photospheric motions (flux...
We study EUV emission line spectra derived from 3D MHD models of structures in the corona, in particular of an active region surrounded by a strong chromospheric network. The 3D MHD models account properly for the energy balance, especially for heat conduction and radiative losses, which allows us to reliably synthesize the profiles of EUV emission...
Using a 3D forward model of the corona we investigate the structure of the base of the corona. Spectral profiles of various emission lines synthesized from the 3D MHD coronal model of Gudiksen & Nordlund (2002, 2005a,b) allow us to compare the source regions of transition region and coronal lines to the magnetic field. By this we can study the conn...