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Author name code: dorch
ADS astronomy entries on 2022-09-14
author:"Dorch, Bertil"
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Title: Astronomical observatory publications: information exchange
before the Internet era
Authors: Ellegaard, Ole; Dorch, Bertil F.
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observatories has now been replaced by the exchange of information via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.
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Title: The history of the Observatory Library at Østervold in
Copenhagen, Denmark
Authors: Dorch, Bertil F.; Petersen, Jørgen Otzen
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.
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Title: The uniqueness of astronomical observatory publications
Authors: Ellegaard, Ole; Dorch, Bertil F.
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.
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Title: Making Tycho Brahe's Sky Accessible to Future Astronomers
Authors: Dorch, Bertil Fabricius; Holck, Jakob Povl; Rasmussen,
Kaare Lund; Christensen, Majken Brahe Ellegaard
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.
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Title: The Cost of Astronomy Publishing fees in astronomy: Is
something rotten in the case of Denmark?
Authors: Dorch, Bertil F.
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.
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Title: The Cost of Astronomy
Authors: Dorch, Bertil F.
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.
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Title: The data sharing advantage in astrophysics
Authors: Dorch, Bertil F.; Drachen, Thea M.; Ellegaard, Ole
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.
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Title: Helicity and Dynamo Action
Authors: Archontis, Vasilis D.; Dorch, Bertil F.
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.
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Title: Spots on the surface of Betelgeuse -- Results from new 3D
stellar convection models
Authors: Freytag, B.; Steffen, M.; Dorch, B.
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
(CO<SUP>5</SUP>BOLD) 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.
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Title: Modelling flux tube dynamics
Authors: Dorch, Bertil
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.
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Title: On the transport of magnetic fields by solar-like stratified
convection
Authors: Dorch, Bertil; Nordlund, Aake
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.
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Title: Numerical Simulations of Dynamos Associated with ABC Flows
Authors: Archontis, V.; Dorch, B.
1999ASPC..178....1A Altcode: 1999sdnc.conf....1A
No abstract at ADS
