1,323 research outputs found
The influence of coronal EUV irradiance on the emission in the He I 10830 A and D3 multiplets
Two of the most attractive spectral windows for spectropolarimetric
investigations of the physical properties of the plasma structures in the solar
chromosphere and corona are the ones provided by the spectral lines of the He I
10830 A and 5876 A (or D3) multiplets, whose polarization signals are sensitive
to the Hanle and Zeeman effects. However, in order to be able to carry out
reliable diagnostics, it is crucial to have a good physical understanding of
the sensitivity of the observed spectral line radiation to the various
competing driving mechanisms. Here we report a series of off-the-limb non-LTE
calculations of the He I D3 and 10830 A emission profiles, focusing our
investigation on their sensitivity to the EUV coronal irradiation and the model
atmosphere used in the calculations. We show in particular that the intensity
ratio of the blue to the red components in the emission profiles of the He I
10830 A multiplet turns out to be a good candidate as a diagnostic tool for the
coronal irradiance. Measurements of this observable as a function of the
distance to the limb and its confrontation with radiative transfer modeling
might give us valuable information on the physical properties of the solar
atmosphere and on the amount of EUV radiation at relevant wavelengths
penetrating the chromosphere from above.Comment: 19 pages, 11 figures (pre-print format). Accepted for publication in
Ap
Exact R\'enyi entropies of -dimensional harmonic systems
The determination of the uncertainty measures of multidimensional quantum
systems is a relevant issue \textit{per se} and because these measures, which
are functionals of the single-particle probability density of the systems,
describe numerous fundamental and experimentally accessible physical
quantities. However, it is a formidable task (not yet solved, except possibly
for the ground and a few lowest-lying energetic states) even for the small
bunch of elementary quantum potentials which are used to approximate the
mean-field potential of the physical systems. Recently, the dominant term of
the Heisenberg and R\'enyi measures of the multidimensional harmonic system
(i.e., a particle moving under the action of a -dimensional quadratic
potential, ) has been analytically calculated in the high-energy (i.e.,
Rydberg) and the high-dimensional (i.e., pseudoclassical) limits. In this work
we determine the exact values of the R\'enyi uncertainty measures of the
-dimensional harmonic system for all ground and excited quantum states
directly in terms of , the potential strength and the hyperquantum numbers.Comment: Accepted in EPJ-S
Dos años de AMLO en México: ¿un gobierno de izquierda?
Un análisis de las polÃticas sociales y laborales revela un progresismo fallido que estarÃa más al centro que a la izquierda del orden neoliberal, escribe Ramón I. Centeno (Universidad de Sonora)
Features of spatial distribution of oscillations in faculae regions
We found that oscillations of LOS velocity in H-alpha are different for
various parts of faculae regions. Power spectra show that the contribution of
low-frequency modes (1.2 - 2 mHz) increase at the network boundaries. Three and
five- minute periods dominate inside cells. The spectra of photosphere and
chromosphere LOS velocity oscillations differ for most faculae. On the other
hand, we detected several cases where propagating oscillations in faculae were
manifest with a five-minute period. Their initiation point on spatial-temporal
diagrams coincided with the local maximum of the longitudinal magnetic field.Comment: 6 pages, 4 figure
All-Dielectric Rod-Type Metamaterials at Optical Frequencies
Light propagation in all-dielectric rod-type metamaterials is studied
theoretically. The electric and magnetic dipole moments of the rods are derived
analytically in the long-wavelength limit. The effective permittivity and
permeability of a square lattice of rods are calculated by homogenizing the
corresponding array of dipoles. The role of dipole resonances in the optical
properties of the rod array is interpreted. This structure is found to exhibit
a true left-handed behavior, confirming previous experiments [L. Peng
\textit{et al.}, Phys. Rev. Lett. \textbf{98}, 157403 (2007)]. A scaling
analysis shows that this effect holds at optical frequencies and can be
obtained by using rods made, for example, of silicon.Comment: 10 pages, 4 figures. The title has been shortened; Figs. 1, 2 and 3
have been modified; Eq. 4 has been corrected (sign error); A few sentences
have been added/rewritte
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