245 research outputs found
Weather Prediction in Babylonia
This paper addresses developments in the prediction of weather phenomena in Late Babylonian scholarly texts. Previously published and unpublished texts are analyzed and the underlying methods are compared with omen-based weather prognostication, developments in Babylonian astronomical prediction and reporting practices in the astronomical diaries. It is found that some texts combine long-term astronomical prediction with inferential methods for predicting weather phenomena. It is argued that these new methods for predicting weather phenomena are part of a larger Babylonian effort to predict and explain non-astronomical phenomena by relating them to predictable astronomical phenomena
Edited with Introduction, Commentary, and Cuneiform Texts. Oxford University Press, Oxford, 2020. (25 cm, XXXII, 464). ISBN 978-0-19-953994-9. $ 140.00.
Introduction
This article introduces a double issue comprising 11 papers about Babylonian and Egyptian priests and scholarship between ca. 600 bce and 200 ce. They constitute the proceedings of the workshop “Scholars, Priests, and Temples: Babylonian and Egyptian Science in Context”, which was held at the Humboldt University Berlin, 12–14 May 2016, with support of the Excellence Cluster TOPOI. The workshop brought together Assyriologists and Egyptologists with expertise in Babylonian and Egyptian scholarship, priesthoods and temple institutions. All contributions have been revised and updated since then. The present contribution offers a brief introduction on previous research, cross-cultural interactions, economic aspects, royal patronage, and internal developments of Babylonian and Egyptian temple scholarship, followed by short summaries of the papers
Performative Aspects of Assyrian Celestial Divination and Babylonian Astronomical Diaries
This contribution explores performative aspects of Assyrian celestial divination and Babylonian astronomical diaries and related texts during the first millennium BCE. While the sources for Assyrian celestial divination contain much evidence about observational and ritual performances, astronomical diaries and related texts are mainly concerned with observation and prediction. It is argued that the Assyrian evidence can shed light on some poorly docu-mented performative aspects of astronomical practices in Babylon
Geodynamo alpha-effect derived from box simulations of rotating magnetoconvection
The equations for fully compressible rotating magnetoconvection are
numerically solved in a Cartesian box assuming conditions roughly suitable for
the geodynamo. The mean electromotive force describing the generation of mean
magnetic flux by convective turbulence in the rotating fluid is directly
calculated from the simulations, and the corresponding alpha-coefficients are
derived. Due to the very weak density stratification the alpha-effect changes
its sign in the middle of the box. It is positive at the top and negative at
the bottom of the convection zone. For strong magnetic fields we also find a
clear downward advection of the mean magnetic field. Both of the simulated
effects have been predicted by quasi-linear computations (Soward, 1979;
Kitchatinov and Ruediger, 1992). Finally, the possible connection of the
obtained profiles of the EMF with mean-field models of oscillating
alpha^2-dynamos is discussed.Comment: 17 pages, 9 figures, submitted to Phys. Earth Planet. Inte
Helicity Observation of Weak and Strong Fields
We report in this letter our analysis of a large sample of photospheric
vector magnetic field measurements. Our sample consists of 17200 vector
magnetograms obtained from January 1997 to August 2004 by Huairou Solar
Observing Station of the Chinese National Astronomical Observatory. Two
physical quantities, and current helicity, are calculated and their
signs and amplitudes are studied in a search for solar cycle variations.
Different from other studies of the same type, we calculate these quantities
for weak () fields separately. For
weak fields, we find that the signs of both and current helicity are
consistent with the established hemispheric rule during most years of the solar
cycle and their magnitudes show a rough tendency of decreasing with the
development of solar cycle. Analysis of strong fields gives an interesting
result: Both and current helicity present a sign opposite to that of
weak fields. Implications of these observations on dynamo theory and helicity
production are also briefly discussed.Comment: accepted for publication in ApJ Lette
Magnetoconvection and dynamo coefficients: II. Field-direction dependent pumping of magnetic field
We study the pumping of magnetic flux in three-dimensional compressible
magnetoconvection in the context of stellar dynamos. The simulation domain
represents a rectangular section from the lower part of a stellar convection
zone plus the underlying stably stratified layer, with a total depth of up to
five pressure scale heights. Once convection has attained a statistically
stationary state, a magnetic field is introduced. The magnetic field is
subsequently modified by the convective motions, and the resulting pumping
effects are isolated by calculating various coefficients of the expansion of
the electromotive force, uxb, in terms of components of the mean magnetic
field. The dependence of the pumping effects on rotation, latitude and other
parameters is studied. First numerical evidence is found for the existence of
pumping effects in the horizontal directions, unless the rotation axis
coincides with the vertical axis, as is the case on the poles. Evidence is
found that the pumping effects act differently on different components of the
mean magnetic field. Latitudinal pumping is mainly equatorward for toroidal
field, and can be poleward for poloidal field. Longitudinal pumping is mainly
retrograde for the radial field but prograde for the latitudinal field. The
pumping effect in the vertical direction is found to be dominated by the
diamagnetic effect, equivalent to a predominating downward advection with a
maximum speed in the turbulent case of about 10 percent of the rms convective
velocity. Where possible, an attempt is made to identify the physical origin of
the effect. Finally, some consequences of the results for stellar dynamos are
discussed.Comment: 12 pages, 9 figures, submitted to A&A; version
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