Author name code: dorch ADS astronomy entries on 2022-09-14 author:"Dorch, Bertil" ------------------------------------------------------------------------ Title: Astronomical observatory publications: information exchange before the Internet era Authors: Ellegaard, Ole; Dorch, Bertil F. Bibcode: 2022JAHH...25...91E Altcode: 2022arXiv220508386E For decades, perhaps even centuries, the exchange of publications between observatories was the most important source of information on new astronomical results, either in the form of observational data or new scientific theories. In particular, small observatories or institutions used this method. The exchange of physical material between observatories has now been replaced by the exchange of information via the Internet. Yet much of the ancient material has never been digitized and can only be found in the few existing collections of observatory publications. A recent donation of such a collection from the University of Copenhagen to our own library at the University of Southern Denmark has led us to investigate the uniqueness of such collections: Which observatories and publications are represented in the collections that still exist today? We also examine the availability of the material in the collections. Title: The history of the Observatory Library at Østervold in Copenhagen, Denmark Authors: Dorch, Bertil F.; Petersen, Jørgen Otzen Bibcode: 2021JAHH...24.1090D Altcode: About fifty years after the work that astronomer Tycho Brahe carried out while living on the island of Hven had made him world famous, King Christian IV of Denmark built the Trinity Buildings in Copenhagen: a students' church, a university library, and an astronomical observatory at the top of the Round Tower. The Tower observatory was opened in 1642, and it housed the astronomers from the University of Copenhagen until 1861 when a new, modern observatory was built at Østervold in the eastern part of the city. In 1996, all the University astronomers from the observatories at Østervold and the small town of Brorfelde were relocated to the Rockefeller Buildings at Østerbro, and the two observatories were closed. Title: The uniqueness of astronomical observatory publications Authors: Ellegaard, Ole; Dorch, Bertil F. Bibcode: 2021IAUS..367..487E Altcode: 2021arXiv210412838E Astronomical observatory publications include the work of local astronomers from observatories around the world and are traditionally exchanged between observatories through their libraries. However, large collections of these publications appear to be rare and are often incomplete. In order to assess the unique properties of the collections, we compare observatories present in our own collection from the university at Copenhagen, Denmark with two collections from the USA: one at the Woodman Library at Wisconsin-Madison and another at the Dudley Observatory in Loudonville, New York. Title: Making Tycho Brahe's Sky Accessible to Future Astronomers Authors: Dorch, Bertil Fabricius; Holck, Jakob Povl; Rasmussen, Kaare Lund; Christensen, Majken Brahe Ellegaard Bibcode: 2019IAUS..349..510D Altcode: Can we make a copy of Tycho's "De Nova Stella" that can in fact survive a nova? At first, this may seem at best a nerdish, if not distinctly foolish question. However, it is also both a technological and a philosophical question: in fact, answering questions like this is linked to both technical, physical and sociological problems related to the long-term preservation and curation of objects from current and past civilizations. Title: The Cost of Astronomy Publishing fees in astronomy: Is something rotten in the case of Denmark? Authors: Dorch, Bertil F. Bibcode: 2018EPJWC.18612005D Altcode: Using Scopus and national sources, I have investigated the evolution of the cost of publishing in Danish astronomy on a fine scale over a number of years. I find that the number of publications per year from Danish astronomers increased by a factor of four during 15 years: naturally, the corresponding potential cost of publishing must have increased similarly. The actual realized cost of publishing in core journals are investigated for a high profile Danish astronomy research institutions. I argue that the situation is highly unstable if the current cost scenario continues, and I speculate that Danish astronomy is risking a scholarly communication collapse due to the combination of increasing subscription cost, increased research output, and increased direct publishing costs related to Open Access and other page charges. Title: The Cost of Astronomy Authors: Dorch, Bertil F. Bibcode: 2017lisa.confP...2D Altcode: Using Scopus and national sources, I have investigated the evolution of the cost of publishing in Danish astronomy on fine scale over a number of years. I find that e.g. the number of publications per year from Danish astronomers increased by a factor of 4 during 15 years: naturally, the corresponding potential cost of publishing increased similarly. The actual realized cost of publishing in core journals are investigated for high profile Danish astronomy research institutions and compared to the corresponding library license expenditures for those particular core journals. It is illustrated that the situation is highly unstable if the current cost scenario continues, and I speculate that Danish astronomy is risking a catastrophic collaps due to the combination of increasing subscription cost, increased research output, and increased direct publishing costs related to Open Access and other page charges. Title: The data sharing advantage in astrophysics Authors: Dorch, Bertil F.; Drachen, Thea M.; Ellegaard, Ole Bibcode: 2016IAUFM..29A.172D Altcode: We present here evidence for the existence of a citation advantage within astrophysics for papers that link to data. Using simple measures based on publication data from NASA Astrophysics Data System we find a citation advantage for papers with links to data receiving on the average significantly more citations per paper than papers without links to data. Furthermore, using INSPEC and Web of Science databases we investigate whether either papers of an experimental or theoretical nature display different citation behavior. Title: Helicity and Dynamo Action Authors: Archontis, Vasilis D.; Dorch, Bertil F. Bibcode: 2003IAUJD...3E..10A Altcode: We performed numerical 3-d MHD simulations to study whether or not the presence of helicity is a necessary ingredient for fast dynamo action. A steady 3-d flow with no mean helicity is used and is turned out that apart from the high growth rate in the linear regime the dynamo saturates at a level significantly higher that the intermittent turbulent dynamos. It becomes clear from this example that the precense of a mean helicity is not at all a requirement for dynamo action but it is rather the stretching ability of the flow that amplifies the magnetic energy in an exponential manner. Title: Spots on the surface of Betelgeuse -- Results from new 3D stellar convection models Authors: Freytag, B.; Steffen, M.; Dorch, B. Bibcode: 2002AN....323..213F Altcode: The observed irregular brightness fluctuations of the well-known red supergiant Betelgeuse (alpha Ori, M2 Iab) have been attributed by M. Schwarzschild (1975) to the changing granulation pattern formed by only a few giant convection cells covering the surface of this giant star. The surface structure revealed by modern interferometric methods appears to be generally consistent with the explanation as large-scale granular intensity fluctuations. The interferometric data can be modeled equally well by assuming the presence of a few (up to 3) unresolved hot or cool spots on a limb-darkened disk. In an effort to improve our theoretical understanding of the Betelgeuse phenomena, we have applied a new radiation hydrodynamics code (CO5BOLD) to the problem of global convection in giant stars. For this purpose, the "local box" setup usually employed for the simulation of solar-type surface convection cannot be used. Rather, we have chosen a radically different approach: the whole star is enclosed in a cube ("star-in-a-box" setup). The properties of the stellar model are defined by the prescribed gravitational central potential and by a special inner boundary condition which replaces the unresolved core, including the source of nuclear energy production. We present current results obtained from this novel generation of 3D stellar convection simulations, proceeding from a toy model ("Mini-Sun") towards the numerically more demanding supergiant regime. We discuss the basic observational properties of Betelgeuse in the light of our best model obtained so far (T_eff = 3300 K, log g = -0.4). Finally, we describe a first attempt to investigate the interaction of the global convective flows with magnetic fields based on the kinematic approximation. Title: Modelling flux tube dynamics Authors: Dorch, Bertil Bibcode: 2002astro.ph..7130D Altcode: Over the last few years, numerical models of the behavior of solar magnetic flux tubes have gone from using methods that were essentially one-dimensional (i.e. the thin flux tube approximation), over more or less idealized two-dimensional simulations, to becoming ever more realistic three-dimensional case studies. Along the way a lot of new knowledge has been picked up as to the e.g. the likely topology of the flux tubes, and the instabilities that they are subjected to etc. Within the context of what one could call the ``flux tube solar dynamo paradigm,'' I will discuss recent results of efforts to study buoyant magnetic flux tubes ascending from deep below the photosphere, before they emerge in active regions and interact with the field in the overlying atmosphere: i.e. I am not addressing the flux tubes associated with magnetic bright points, which possibly are generated by a small-scale dynamo operating in the solar photosphere. The presented efforts are numerical MHD simulations of twisted flux ropes and loops, interacting with rotation and convection. Ultimately the magnetic surface signatures of these simulations, when compared to observations, constraints the dynamo processes that are responsible for the generation of the flux ropes in the first place. Along with these new results several questions pop up (both old and new ones), regarding the nature of flux tubes and consequently of the solar dynamo. Title: On the transport of magnetic fields by solar-like stratified convection Authors: Dorch, Bertil; Nordlund, Aake Bibcode: 2000astro.ph..6358D Altcode: The interaction of magnetic fields and stratified convection was studied in the context of the solar and late type stellar dynamos by using numerical 3D MHD simulations. The topology of stratified asymmetric and over-turning convection enables a pumping mechanism that may render the magnetic flux storage problem obsolete. The inclusion of open boundary conditions leads to a considerable flux loss unless the open boundary is placed close to the physical boundary. Simulations including solar-like latitudinal shear indicates that a toroidal field of several tens of kilo-Gauss may be held down by the pumping mechanism. Title: Numerical Simulations of Dynamos Associated with ABC Flows Authors: Archontis, V.; Dorch, B. Bibcode: 1999ASPC..178....1A Altcode: 1999sdnc.conf....1A No abstract at ADS