96,425 research outputs found
Bayesian evaluation of the southern hemisphere radiocarbon offset during the holocene
While an interhemispheric offset in atmospheric radiocarbon levels from AD 1950â950 is now well established, its existence earlier in the Holocene is less clear, with some studies reporting globally uniform 14C levels while others finding Southern Hemisphere samples older by a few decades. In this paper, we present a method for wiggle-matching Southern Hemisphere data sets against Northern Hemisphere curves, using the Bayesian calibration program OxCal 4.1 with the Reservoir Offset function accommodating a potential interhemispheric offset. The accuracy and robustness of this approach is confirmed by wiggle-matching known-calendar age sequences of the Southern Hemisphere calibration curve SHCal04 against the Northern Hemisphere curve IntCal04. We also show that 5 of 9 Holocene Southern Hemisphere data sets are capable of yielding reliable offset information. Those data sets that are accurate and precise show that interhemispheric offset levels in the Early Holocene are similar to modern levels, confirming SHCal04 as the curve of choice for calibrating Southern Hemisphere samples
Variations of radiocarbon in tree rings: southern hemisphere offset preliminary results
The Queen's University of Belfast, Northern Ireland and University of Waikato, Hamilton, New Zealand radiocarbon laboratories have undertaken a series of high-precision measurements on decadal samples of dendrochronologically dated oak (Quercus patrea) and cedar (Libocedrus bidwillii) from Great Britain and New Zealand, respectively. The results show a real atmospheric offset of 3.4 ± 0.6% (27.2 ± 4.7 ÂčâŽC yr) between the two locations for the interval AD 1725 to AD 1885, with the Southern Hemisphere being depleted in ÂčâŽC. This result is less than the value currently used to correct Southern Hemisphere calibrations, possibly indicating a gradient in ÎÂčâŽC within the Southern Hemisphere
Southern Hemisphere automated supernova search
The Perth Astronomy Research Group has developed an automated supernova search program, using the 61 cm PerthâLowell reflecting telescope at Perth Observatory in Western Australia, equipped with a CCD camera. The system is currently capable of observing about 15 objects per hour, using 3 min exposures, and has a detection threshold of 18thâ19th magnitude. The entire system has been constructed using lowâcost IBMâcompatible computers. Two original discoveries (SN 1993K, SN 1994R) have so far been made during automated search runs. This paper describes the hardware and software used for the supernova search program, and shows some preliminary results from the search system
SHCal04 Southern Hemisphere Calibration, 0â11.0 cal kyr BP
Recent measurements on dendrochronologically-dated wood from the Southern Hemisphere have shown that there are differences between the structural form of the radiocarbon calibration curves from each hemisphere. Thus, it is desirable, when possible, to use calibration data obtained from secure dendrochronologically-dated wood from the corresponding hemisphere. In this paper, we outline the recent work and point the reader to the internationally recommended data set that should be used for future calibration of Southern Hemisphere ÂčâŽC dates
The 1991 southern hemisphere complex of activity
We have investigated the development of a complex of activity which took place in the southern hemisphere of the Sun between July 1991 and April 1992. The whole process culminated with the successive formation of two large active regions with sunspot groups NOAA 6850 (September/October) and NOAA 6891 (October/November 1991), both having complicated magnetic ïŹelds, but the former without heavy ïŹare activity. We observed the appearance of the individual active regions as the consequence of the development stage of large-scale magnetic ïŹelds in the given area of the solar surface, in connection with their longitudinal and latitudinal distribution. We have studied the dynamics of this development on magnetic synoptic charts, as well as on spectroheliograms taken in the K-line of ionized calcium. Our new observations conïŹrm the regularities found earlier and connection of global and local developments with convection. We think that they could become a tool for solar activity prediction and that they could be used for comparative studies of stellar complexes of activity
Southern Hemisphere meteor rates Final report
Diurnal variations of Southern Hemisphere meteor rat
Helicity at Photospheric and Chromospheric Heights
In the solar atmosphere the twist parameter has the same sign as
magnetic helicity. It has been observed using photospheric vector magnetograms
that negative/positive helicity is dominant in the northern/southern hemisphere
of the Sun. Chromospheric features show dextral/sinistral dominance in the
northern/southern hemisphere and sigmoids observed in X-rays also have a
dominant sense of reverse-S/forward-S in the northern/southern hemisphere. It
is of interest whether individual features have one-to-one correspondence in
terms of helicity at different atmospheric heights. We use UBF \Halpha images
from the Dunn Solar Telescope (DST) and other \Halpha data from Udaipur Solar
Observatory and Big Bear Solar Observatory. Near-simultaneous vector
magnetograms from the DST are used to establish one-to-one correspondence of
helicity at photospheric and chromospheric heights. We plan to extend this
investigation with more data including coronal intensities.Comment: 5 pages, 1 figure, 1 table To appear in "Magnetic Coupling between
the Interior and the Atmosphere of the Sun", eds. S.S. Hasan and R.J. Rutten,
Astrophysics and Space Science Proceedings, Springer-Verlag, Heidelberg,
Berlin, 200
Southern hemisphere stratospheric circulation as indicated by shipboard meteorological rocket observations
Southern Hemisphere stratospheric circulation as indicated by shipboard meteorological rocket observation
Evidence for Astrophysical Muon Neutrinos from the Northern Sky with IceCube
Results from the IceCube Neutrino Observatory have recently provided
compelling evidence for the existence of a high energy astrophysical neutrino
flux utilizing a dominantly Southern Hemisphere dataset consisting primarily of
nu_e and nu_tau charged current and neutral current (cascade) neutrino
interactions. In the analysis presented here, a data sample of approximately
35,000 muon neutrinos from the Northern sky was extracted from data taken
during 659.5 days of livetime recorded between May 2010 and May 2012. While
this sample is composed primarily of neutrinos produced by cosmic ray
interactions in the Earth's atmosphere, the highest energy events are
inconsistent with a hypothesis of solely terrestrial origin at 3.7 sigma
significance. These neutrinos can, however, be explained by an astrophysical
flux per neutrino flavor at a level of Phi(E_nu) = 9.9^{+3.9}_{-3.4} times
10^{-19} GeV^{-1} cm^{-2} sr^{-1} s^{-1} ({E_nu / 100 TeV})^{-2}, consistent
with IceCube's Southern Hemisphere dominated result. Additionally, a fit for an
astrophysical flux with an arbitrary spectral index was performed. We find a
spectral index of 2.2^{+0.2}_{-0.2}, which is also in good agreement with the
Southern Hemisphere result.Comment: 4 figures, 2, tables, includes supplementary materia
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