353 research outputs found
A methodology for attributing the role of climate change in extreme events: a global spectrally nudged storyline
Extreme weather events are generally associated with unusual dynamical conditions, yet the signal-to-noise ratio of the dynamical aspects of climate change that are relevant to extremes appears to be small, and the nature of the change can be highly uncertain. On the other hand, the thermodynamic aspects of climate change are already largely apparent from observations, and are far more certain since they are anchored in agreed-upon physical understanding. The storyline method of extreme event attribution, which has been gaining traction in recent years, quantitatively estimates the magnitude of thermodynamic aspects of climate change, given the dynamical conditions. There are different ways of imposing the dynamical conditions. Here we present and evaluate a method where the dynamical conditions are enforced through global spectral nudging towards reanalysis data of the large-scale vorticity and divergence in the free atmosphere, leaving the lower atmosphere free to respond. We simulate the historical extreme weather event twice: first in the world as we know it, with the events occurring on a background of a changing climate, and second in a âcounterfactualâ world, where the background is held fixed over the past century. We describe the methodology in detail, and present results for the European 2003 heatwave and the Russian 2010 heatwave as a proof of concept. These show that the conditional attribution can be performed with a high signal-to-noise ratio on daily timescales and at local spatial scales. Our methodology is thus potentially highly useful for realistic stress testing of resilience strategies for climate impacts, when coupled to an impact model
Limits on diffuse fluxes of high energy extraterrestrial neutrinos with the AMANDA-B10 detector
Data from the AMANDA-B10 detector taken during the austral winter of 1997
have been searched for a diffuse flux of high energy extraterrestrial
muon-neutrinos, as predicted from, e.g., the sum of all active galaxies in the
universe. This search yielded no excess events above those expected from the
background atmospheric neutrinos, leading to upper limits on the
extraterrestrial neutrino flux. For an assumed E^-2 spectrum, a 90% classical
confidence level upper limit has been placed at a level E^2 Phi(E) = 8.4 x
10^-7 GeV cm^-2 s^-1 sr^-1 (for a predominant neutrino energy range 6-1000 TeV)
which is the most restrictive bound placed by any neutrino detector. When
specific predicted spectral forms are considered, it is found that some are
excluded.Comment: Submitted to Physical Review Letter
Search for Point Sources of High Energy Neutrinos with AMANDA
This paper describes the search for astronomical sources of high-energy
neutrinos using the AMANDA-B10 detector, an array of 302 photomultiplier tubes,
used for the detection of Cherenkov light from upward traveling
neutrino-induced muons, buried deep in ice at the South Pole. The absolute
pointing accuracy and angular resolution were studied by using coincident
events between the AMANDA detector and two independent telescopes on the
surface, the GASP air Cherenkov telescope and the SPASE extensive air shower
array. Using data collected from April to October of 1997 (130.1 days of
livetime), a general survey of the northern hemisphere revealed no
statistically significant excess of events from any direction. The sensitivity
for a flux of muon neutrinos is based on the effective detection area for
through-going muons. Averaged over the Northern sky, the effective detection
area exceeds 10,000 m^2 for E_{mu} ~ 10 TeV. Neutrinos generated in the
atmosphere by cosmic ray interactions were used to verify the predicted
performance of the detector. For a source with a differential energy spectrum
proportional to E_{nu}^{-2} and declination larger than +40 degrees, we obtain
E^2(dN_{nu}/dE) <= 10^{-6}GeVcm^{-2}s^{-1} for an energy threshold of 10 GeV.Comment: 46 pages, 22 figures, 4 tables, submitted to Ap.
IceCube - the next generation neutrino telescope at the South Pole
IceCube is a large neutrino telescope of the next generation to be
constructed in the Antarctic Ice Sheet near the South Pole. We present the
conceptual design and the sensitivity of the IceCube detector to predicted
fluxes of neutrinos, both atmospheric and extra-terrestrial. A complete
simulation of the detector design has been used to study the detector's
capability to search for neutrinos from sources such as active galaxies, and
gamma-ray bursts.Comment: 8 pages, to be published with the proceedings of the XXth
International Conference on Neutrino Physics and Astrophysics, Munich 200
Muon Track Reconstruction and Data Selection Techniques in AMANDA
The Antarctic Muon And Neutrino Detector Array (AMANDA) is a high-energy
neutrino telescope operating at the geographic South Pole. It is a lattice of
photo-multiplier tubes buried deep in the polar ice between 1500m and 2000m.
The primary goal of this detector is to discover astrophysical sources of high
energy neutrinos. A high-energy muon neutrino coming through the earth from the
Northern Hemisphere can be identified by the secondary muon moving upward
through the detector. The muon tracks are reconstructed with a maximum
likelihood method. It models the arrival times and amplitudes of Cherenkov
photons registered by the photo-multipliers. This paper describes the different
methods of reconstruction, which have been successfully implemented within
AMANDA. Strategies for optimizing the reconstruction performance and rejecting
background are presented. For a typical analysis procedure the direction of
tracks are reconstructed with about 2 degree accuracy.Comment: 40 pages, 16 Postscript figures, uses elsart.st
Sensitivity of the IceCube Detector to Astrophysical Sources of High Energy Muon Neutrinos
We present the results of a Monte-Carlo study of the sensitivity of the
planned IceCube detector to predicted fluxes of muon neutrinos at TeV to PeV
energies. A complete simulation of the detector and data analysis is used to
study the detector's capability to search for muon neutrinos from sources such
as active galaxies and gamma-ray bursts. We study the effective area and the
angular resolution of the detector as a function of muon energy and angle of
incidence. We present detailed calculations of the sensitivity of the detector
to both diffuse and pointlike neutrino emissions, including an assessment of
the sensitivity to neutrinos detected in coincidence with gamma-ray burst
observations. After three years of datataking, IceCube will have been able to
detect a point source flux of E^2*dN/dE = 7*10^-9 cm^-2s^-1GeV at a 5-sigma
significance, or, in the absence of a signal, place a 90% c.l. limit at a level
E^2*dN/dE = 2*10^-9 cm^-2s^-1GeV. A diffuse E-2 flux would be detectable at a
minimum strength of E^2*dN/dE = 1*10^-8 cm^-2s^-1sr^-1GeV. A gamma-ray burst
model following the formulation of Waxman and Bahcall would result in a 5-sigma
effect after the observation of 200 bursts in coincidence with satellite
observations of the gamma-rays.Comment: 33 pages, 13 figures, 6 table
Limits to the muon flux from WIMP annihilation in the center of the Earth with the AMANDA detector
A search for nearly vertical up-going muon-neutrinos from neutralino
annihilations in the center of the Earth has been performed with the AMANDA-B10
neutrino detector. The data sample collected in 130.1 days of live-time in
1997, ~10^9 events, has been analyzed for this search. No excess over the
expected atmospheric neutrino background is oberved. An upper limit at 90%
confidence level on the annihilation rate of neutralinos in the center of the
Earth is obtained as a function of the neutralino mass in the range 100
GeV-5000 GeV, as well as the corresponding muon flux limit.Comment: 14 pages, 11 figures. Version accepted for publication in Physical
Review
Results from the Antarctic Muon and Neutrino Detector Array (AMANDA)
We show new results from both the older and newer incarnations of AMANDA
(AMANDA-B10 and AMANDA-II, respectively). These results demonstrate that AMANDA
is a functioning, multipurpose detector with significant physics and
astrophysics reach. They include a new higher-statistics measurement of the
atmospheric muon neutrino flux and preliminary results from searches for a
variety of sources of ultrahigh energy neutrinos: generic point sources,
gamma-ray bursters and diffuse sources producing muons in the detector, and
diffuse sources producing electromagnetic or hadronic showers in or near the
detector.Comment: Invited talk at the XXth International Conference on Neutrino Physics
and Astrophysics (Neutrino 2002), Munich, Germany, May 25-30, 200
On the selection of AGN neutrino source candidates for a source stacking analysis with neutrino telescopes
The sensitivity of a search for sources of TeV neutrinos can be improved by
grouping potential sources together into generic classes in a procedure that is
known as source stacking. In this paper, we define catalogs of Active Galactic
Nuclei (AGN) and use them to perform a source stacking analysis. The grouping
of AGN into classes is done in two steps: first, AGN classes are defined, then,
sources to be stacked are selected assuming that a potential neutrino flux is
linearly correlated with the photon luminosity in a certain energy band (radio,
IR, optical, keV, GeV, TeV). Lacking any secure detailed knowledge on neutrino
production in AGN, this correlation is motivated by hadronic AGN models, as
briefly reviewed in this paper.
The source stacking search for neutrinos from generic AGN classes is
illustrated using the data collected by the AMANDA-II high energy neutrino
detector during the year 2000. No significant excess for any of the suggested
groups was found.Comment: 43 pages, 12 figures, accepted by Astroparticle Physic
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