206 research outputs found
The role of the Fraunhofer lines in solar brightness variability
The solar brightness varies on timescales from minutes to decades. A clear
identification of the physical processes behind such variations is needed for
developing and improving physics-based models of solar brightness variability
and reconstructing solar brightness in the past. This is, in turn, important
for better understanding the solar-terrestrial and solar-stellar connections.
We estimate the relative contributions of the continuum, molecular, and
atomic lines to the solar brightness variations on different timescales.
Our approach is based on the assumption that variability of the solar
brightness on timescales greater than a day is driven by the evolution of the
solar surface magnetic field. We calculated the solar brightness variations
employing the solar disc area coverage of magnetic features deduced from the
MDI/SOHO observations. The brightness contrasts of magnetic features relative
to the quiet Sun were calculated with a non-LTE radiative transfer code as
functions of disc position and wavelength. By consecutive elimination of
molecular and atomic lines from the radiative transfer calculations, we
assessed the role of these lines in producing solar brightness variability.
We show that the variations in Fraunhofer lines define the amplitude of the
solar brightness variability on timescales greater than a day and even the
phase of the total solar irradiance variability over the 11-year cycle. We also
demonstrate that molecular lines make substantial contribution to solar
brightness variability on the 11-year activity cycle and centennial timescales.
In particular, our model indicates that roughly a quarter of the total solar
irradiance variability over the 11-year cycle originates in molecular lines.
The maximum of the absolute spectral brightness variability on timescales
greater than a day is associated with the CN violet system between 380 and 390
nm.Comment: 9 pages, 4 figures, accepted for publication in
Astronomy&Astrophysic
Reflection of electrons from a domain wall in magnetic nanojunctions
Electronic transport through thin and laterally constrained domain walls in
ferromagnetic nanojunctions is analyzed theoretically. The description is
formulated in the basis of scattering states. The resistance of the domain wall
is calculated in the regime of strong electron reflection from the wall. It is
shown that the corresponding magnetoresistance can be large, which is in a
qualitative agreement with recent experimental observations. We also calculate
the spin current flowing through the wall and the spin polarization of electron
gas due to reflections from the domain wall.Comment: 7 pages, 4 figure
Magnetoresistance of a semiconducting magnetic wire with domain wall
We investigate theoretically the influence of the spin-orbit interaction of
Rashba type on the magnetoresistance of a semiconducting ferromagnetic
nanostructure with a laterally constrained domain wall. The domain wall is
assumed sharp (on the scale of the Fermi wave length of the charge carriers).
It is shown that the magnetoresistance in such a case can be considerably
large, which is in a qualitative agreement with recent experimental
observations. It is also shown that spin-orbit interaction may result in an
increase of the magnetoresistance. The role of localization corrections is also
briefly discussed.Comment: 5 pages, 2 figure
The impact of innovations in the production of biologically valuable food products on supply chain management in the regional economy
Abstractâ The article shows a study of the role of supply chain management of innovative biologically valuable food products in the industrial development and economy of the region. The analysis of the process of updating the assortment of food products based on the introduction of innovative developments and production principles conducive to the release of a healthy diet product (innovative product) is presented. The main provisions of the concept of healthy food products, the category of âinnovative food productsâ are analyzed. The article systematizes the definitions of the concept of âinnovative productâ. Based on the results of the study, features, functional properties and characteristic features of an innovative food product are determined. Based on the concept of âinnovative food productâ, the concepts of ânew food productâ, âimproved food productâ, and âmodified food productâ are formulated. A classification model of innovative food products is presented. Based on it, it is shown that the development, production and sale of an innovative food product two functions: economic and social. The study made it possible to formulate the main criteria that make it possible to attribute a food product to a group of innovative food products. The article describes the characteristics of an innovative food product, describes market and consumer properties. The author's definitions of concepts are given: âinnovative food productâ, ânew food productâ, âimproved food productâ, âmodified food productâ. A classification of innovative food products is proposed
Experimental Observation of the Inverse Proximity Effect in Superconductor/Ferromagnet Layered Structures
We have studied the nuclear magnetic resonance (NMR) of 51V nuclei in the
superconductor/ferromagnet thin film heterostructures Ni/V/Ni and
Pd{1-x}Fe{x}/V/Pd{1-x}Fe{x} in the normaland superconducting state. Whereas the
position and shape of the NMR line in the normal state for the trilayers is
identical to that observed in a single V-layer, in the superconducting state
the line shape definitely changes, developing a systematic distortion of the
high-field wing of the resonance line. We consider this as the first
experimental evidence for the penetration of ferromagnetism into the
superconducting layer, a phenomenon which has been theoretically predicted
recently and dubbed the inverse proximity effect.Comment: about 5 pages, 3 figures, 1 tabl
On the hyperfine interaction in rare-earth Van Vleck paramagnets at high magnetic fields
An influence of high magnetic fields on hyperfine interaction in the
rare-earth ions with non-magnetic ground state (Van Vleck ions) is
theoretically investigated for the case of ion in axial symmetrical
crystal electric field (ethylsulphate crystal). It is shown that magnetic-field
induced distortions of -electron shell lead to essential changes in
hyperfine magnetic field at the nucleus. The proposed theoretical model is in
agreement with recent experimental data.Comment: 4 pages, no figures, submitted to J. Phys. : Cond. Mat
Resistance of a domain wall in the quasiclassical approach
Starting from a simple microscopic model, we have derived a kinetic equation
for the matrix distribution function. We employed this equation to calculate
the conductance in a mesoscopic F'/F/F' structure with a domain wall (DW).
In the limit of a small exchange energy and an abrupt DW, the conductance
of the structure is equal to . Assuming that the scattering times
for electrons with up and down spins are close to each other we show that the
account for a finite width of the DW leads to an increase in this conductance.
We have also calculated the spatial distribution of the electric field in the F
wire. In the opposite limit of large (adiabatic variation of the
magnetization in the DW) the conductance coincides in the main approximation
with the conductance of a single domain structure . The account for rotation of
the magnetization in the DW leads to a negative correction to this conductance.
Our results differ from the results in papers published earlier.Comment: 11 pages; replaced with revised versio
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