958 research outputs found
Historical Pageantry and the "Fusion of the Races" at the Tercentenary of Quebec, 1908
Complex political and circumstantial forces worked to transform a modest municipal
celebration of the 300th anniversary of Champlainâs founding of his habitation
at Quebec into the Tercentenary of the Founding of Canada. The centrepiece of the
spectacle was the series of historical pageants produced by a British pageant
director with the advice of members of the ComitĂ© dâhistoire et dâarchĂ©ologie of
Quebec. In a combination of careful selection, deft balancing, and misrepresentation
of fact, the powerful and lavish theatre of the pageants displayed a view of Canadian
history designed to serve explicit contemporary political goals.Des forces politiques et circonstancielles complexes se sont conjuguées pour transformer
une modeste fĂȘte municipale du 300e anniversaire de la fondation de QuĂ©bec
par Champlain en tricentenaire de la fondation du Canada. Le clou du spectacle
fut la série de spectacles historiques produits par un directeur de reconstitutions
historiques avec les conseils des membres du ComitĂ© dâhistoire et dâarchĂ©ologie de
Québec. Alliant un choix judicieux, un habile équilibre et une présentation erronée
des faits, le théùtre puissant et somptueux des reconstitutions brossait un tableau
de lâhistoire canadienne conçu explicitement Ă des fins politiques contemporaines
Polarized radio emission from extensive air showers measured with LOFAR
We present LOFAR measurements of radio emission from extensive air showers.
We find that this emission is strongly polarized, with a median degree of
polarization of nearly , and that the angle between the polarization
direction of the electric field and the Lorentz force acting on the particles,
depends on the observer location in the shower plane. This can be understood as
a superposition of the radially polarized charge-excess emission mechanism,
first proposed by Askaryan and the geomagnetic emission mechanism proposed by
Kahn and Lerche. We calculate the relative strengths of both contributions, as
quantified by the charge-excess fraction, for individual air showers. We
find that the measured charge-excess fraction is higher for air showers
arriving from closer to the zenith. Furthermore, the measured charge-excess
fraction also increases with increasing observer distance from the air shower
symmetry axis. The measured values range from for very
inclined air showers at to for almost
vertical showers at . Both dependencies are in qualitative
agreement with theoretical predictions.Comment: 22 pages, 14 figures, accepted for publication in JCA
The radio emission pattern of air showers as measured with LOFAR - a tool for the reconstruction of the energy and the shower maximum
The pattern of the radio emission of air showers is finely sampled with the
Low-Frequency ARray (LOFAR). A set of 382 measured air showers is used to test
a fast, analytic parameterization of the distribution of pulse powers. Using
this parameterization we are able to reconstruct the shower axis and give
estimators for the energy of the air shower as well as the distance to the
shower maximum.Comment: 15 pages, 10 figures, accepted for publication in JCA
A method for high precision reconstruction of air shower Xmax using two-dimensional radio intensity profiles
The mass composition of cosmic rays contains important clues about their
origin. Accurate measurements are needed to resolve long-standing issues such
as the transition from Galactic to extragalactic origin, and the nature of the
cutoff observed at the highest energies. Composition can be studied by
measuring the atmospheric depth of the shower maximum Xmax of air showers
generated by high-energy cosmic rays hitting the Earth's atmosphere. We present
a new method to reconstruct Xmax based on radio measurements. The radio
emission mechanism of air showers is a complex process that creates an
asymmetric intensity pattern on the ground. The shape of this pattern strongly
depends on the longitudinal development of the shower. We reconstruct Xmax by
fitting two-dimensional intensity profiles, simulated with CoREAS, to data from
the LOFAR radio telescope. In the dense LOFAR core, air showers are detected by
hundreds of antennas simultaneously. The simulations fit the data very well,
indicating that the radiation mechanism is now well-understood. The typical
uncertainty on the reconstruction of Xmax for LOFAR showers is 17 g/cm^2.Comment: 12 pages, 10 figures, submitted to Phys. Rev.
Inferring the time-dependent complex Ginzburg-Landau equation from modulus data
We present a formalism for inferring the equation of evolution of a complex
wave field that is known to obey an otherwise unspecified (2+1)-dimensional
time-dependent complex Ginzburg-Landau equation, given field moduli over three
closely-spaced planes. The phase of the complex wave field is retrieved via a
non-interferometric method, and all terms in the equation of evolution are
determined using only the magnitude of the complex wave field. The formalism is
tested using simulated data for a generalized nonlinear system with a
single-component complex wave field. The method can be generalized to
multi-component complex fields.Comment: 9 pages, 9 figure
Cosmic Ray Physics with the LOFAR Radio Telescope
The LOFAR radio telescope is able to measure the radio emission from cosmic
ray induced air showers with hundreds of individual antennas. This allows for
precision testing of the emission mechanisms for the radio signal as well as
determination of the depth of shower maximum , the shower observable
most sensitive to the mass of the primary cosmic ray, to better than 20
g/cm. With a densely instrumented circular area of roughly 320 m, LOFAR
is targeting for cosmic ray astrophysics in the energy range -
eV. In this contribution we give an overview of the status, recent
results, and future plans of cosmic ray detection with the LOFAR radio
telescope.Comment: Proceedings of the 26th Extended European Cosmic Ray Symposium
(ECRS), Barnaul/Belokurikha, 201
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