46,981 research outputs found
Validity of the Taylor Hypothesis for Linear Kinetic Waves in the Weakly Collisional Solar Wind
The interpretation of single-point spacecraft measurements of solar wind
turbulence is complicated by the fact that the measurements are made in a frame
of reference in relative motion with respect to the turbulent plasma. The
Taylor hypothesis---that temporal fluctuations measured by a stationary probe
in a rapidly flowing fluid are dominated by the advection of spatial structures
in the fluid rest frame---is often assumed to simplify the analysis. But
measurements of turbulence in upcoming missions, such as Solar Probe Plus,
threaten to violate the Taylor hypothesis, either due to slow flow of the
plasma with respect to the spacecraft or to the dispersive nature of the plasma
fluctuations at small scales. Assuming that the frequency of the turbulent
fluctuations is characterized by the frequency of the linear waves supported by
the plasma, we evaluate the validity of the Taylor hypothesis for the linear
kinetic wave modes in the weakly collisional solar wind. The analysis predicts
that a dissipation range of solar wind turbulence supported by whistler waves
is likely to violate the Taylor hypothesis, while one supported by kinetic
Alfven waves is not.Comment: 10 pages, 3 figures, Accepted for publication in The Astrophysical
Journa
Quantitative analysis of flare accelerated electrons through their hard X-ray and microwave radiation
Hard X-ray and microwave modelling that takes into account the temporal evolution of the electron spectrum as well as the inhomogeneity of the magnetic field and the ambient medium in the radio source is presented. This method is illustrated for the June 29 1980 10:41 UT event. The implication on the process of acceleration/injection is discussed
Strongly Coupled Matter-Field and Non-Analytic Decay Rate of Dipole Molecules in a Waveguide
The decay rate \gam of an excited dipole molecule inside a waveguide is
evaluated for the strongly coupled matter-field case near a cutoff frequency
\ome_c without using perturbation analysis. Due to the singularity in the
density of photon states at the cutoff frequency, we find that \gam depends
non-analytically on the coupling constant as . In contrast
to the ordinary evaluation of \gam which relies on the Fermi golden rule
(itself based on perturbation analysis), \gam has an upper bound and does not
diverge at \ome_c even if we assume perfect conductance in the waveguide
walls. As a result, again in contrast to the statement found in the literature,
the speed of emitted light from the molecule does not vanish at \ome_c and is
proportional to which is on the order of m/s for
typical dipole molecules.Comment: 4 pages, 2 figure
Heterogeneous Capital, Entrepreneurship, and Economic Organization
We outline an Austrian approach to economic organization based on the entrepreneur and the Austrian idea of capital as heterogeneous and time-dimensioned, tow themes associated with Israel Kirzner's contributions. We provide a novel interpretation of capital heterogeneity based on the notion of attributes, argue that attributes are costly to measure and that this links directly to the theory of economic organization. In particular, we develop insights in economic organization based on the notion that entrepreneurs will often have to experiment with capital assets to gauge the value of these assets when deployed in production.Austrian Economics, capital, knowledge
Jet reconstruction and jet background classification with the ALICE experiment in PbPb collisions at the LHC
For a quantitative interpretation of reconstructed jet properties in
heavy-ion collisions it is paramount to characterize the contribution from the
underlying event and the influence of background fluctuations on the jet
signal. In addition to the pure number fluctuations, region-to-region
correlated background within one event can enhance or deplete locally the level
of background and modify the jet energy. We show a first detailed assessment of
background effects using different probes embedded into heavy-ion data and
quantify their influence on the reconstructed jet spectrum.Comment: 4 pages, 2 figures, Proceedings for the XXII International Conference
on Ultra-Relativistic Nucleus-Nucleus Collisions, Quark Matter 2011, Annec
SAY HAY AND HAY WEST: CHARITY, GOVERNMENT AND FARMER RESPONSES TO THE 2002 DROUGHT IN WESTERN CANADA
Crop Production/Industries,
Solar Energetic Particle Events in the 23rd Solar Cycle: Interplanetary Magnetic Field Configuration and Statistical Relationship with Flares and CMEs
We study the influence of the large-scale interplanetary magnetic field
configuration on the solar energetic particles (SEPs) as detected at different
satellites near Earth and on the correlation of their peak intensities with the
parent solar activity. We selected SEP events associated with X and M-class
flares at western longitudes, in order to ensure good magnetic connection to
Earth. These events were classified into two categories according to the global
interplanetary magnetic field (IMF) configuration present during the SEP
propagation to 1AU: standard solar wind or interplanetary coronal mass
ejections (ICMEs). Our analysis shows that around 20% of all particle events
are detected when the spacecraft is immersed in an ICME. The correlation of the
peak particle intensity with the projected speed of the SEP-associated coronal
mass ejection is similar in the two IMF categories of proton and electron
events, . The SEP events within ICMEs show stronger correlation
between the peak proton intensity and the soft X-ray flux of the associated
solar flare, with correlation coefficient 0.670.13, compared to the
SEP events propagating in the standard solar wind, 0.360.13. The
difference is more pronounced for near-relativistic electrons. The main reason
for the different correlation behavior seems to be the larger spread of the
flare longitude in the SEP sample detected in the solar wind as compared to SEP
events within ICMEs. We discuss to which extent observational bias, different
physical processes (particle injection, transport, etc.), and the IMF
configuration can influence the relationship between SEPs and coronal activity.Comment: http://adsabs.harvard.edu.ezproxy.obspm.fr/abs/2013SoPh..282..579
Kerman-Klein-Donau-Frauendorf model for odd-odd nuclei: formal theory
The Kerman-Klein-Donau-Frauendorf (KKDF) model is a linearized version of the
Kerman-Klein (equations of motion) formulation of the nuclear many-body
problem. In practice, it is a generalization of the standard core-particle
coupling model that, like the latter, provides a description of the
spectroscopy of odd nuclei in terms of the properties of neighboring even
nuclei and of single-particle properties, that are the input parameters of the
model. A divers sample of recent applications attest to the usefulness of the
model. In this paper, we first present a concise general review of the
fundamental equations and properties of the KKDF model. We then derive a
corresponding formalism for odd-odd nuclei that relates their properties to
those of four neighboring even nuclei, all of which enter if one is to include
both multipole and pairing forces. We treat these equations in two ways. In the
first we make essential use of the solutions of the neighboring odd nucleus
problem, as obtained by the KKDF method. In the second, we relate the
properties of the odd-odd nuclei directly to those of the even nuclei. For both
choices, we derive equations of motion, normalization conditions, and an
expression for transition amplitudes. We also solve the problem of choosing the
subspace of physical solutions that arises in an equations of motion approach
that includes pairing interactions.Comment: 27 pages, Late
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