scholarly journals Chromospheric diagnosis with forward scattering polarization

2014 ◽  
Vol 10 (S305) ◽  
pp. 146-153
Author(s):  
E. S. Carlin
Keyword(s):  
Radiative Transfer ◽  
Solar Disk ◽  
Disk Center ◽  
Forward Scattering ◽  
Dynamic Effects ◽  
Polarity Inversion ◽  
Physical Context ◽  
Hanle Effect ◽  
Definition Of ◽  
Spatial Maps

AbstractIs it physically feasible to perform the chromospheric diagnosis using spatial maps of scattering polarization at the solar disk center? To investigate it we synthesized polarization maps (in 8542 Å) resulting from MHD solar models and NLTE radiative transfer calculations that consider Hanle effect and vertical macroscopic motions. After explaining the physical context of forward scattering and presenting our results, we arrive at the definition of Hanle polarity inversion lines. We show how such features can give support for a clearer chromospheric diagnosis in which the magnetic and dynamic effects in the scattering polarization could be disentangled.

scholarly journals Evolution of Stokes V area asymmetry related to a quiet Sun cancellation observed with GRIS/IFU

2020 ◽  
Vol 634 ◽  
pp. A131
Author(s):  
A. J. Kaithakkal ◽  
J. M. Borrero ◽  
C. E. Fischer ◽  
C. Dominguez-Tagle ◽  
M. Collados
Keyword(s):  
Magnetic Flux ◽  
Opposite Polarity ◽  
Disk Center ◽  
Significant Rise ◽  
Polarity Inversion ◽  
Quiet Sun ◽  
Additional Information ◽  
Line Core ◽  
Polarity Inversion Line ◽  
Field Unit

A quiet Sun magnetic flux cancellation event at the disk center was recorded using the Integral Field Unit (IFU) mounted on the GREGOR Infrared Spectrograph (GRIS). The GRIS instrument sampled the event in the photospheric Si I 10827 Å spectral line. The cancellation was preceded by a significant rise in line core intensity and excitation temperature, which is inferred from Stokes inversions under local thermodynamic equilibrium (LTE). The opposite polarity features seem to undergo reconnection above the photosphere. We also found that the border pixels neighboring the polarity inversion line of one of the polarities exhibit a systematic variation of area asymmetry. Area asymmetry peaks right after the line core intensity enhancement and gradually declines thereafter. Analyzing Stokes profiles recorded from either side of the polarity inversion line could therefore potentially provide additional information on the reconnection process related to magnetic flux cancellation. Further analysis without assuming LTE will be required to fully characterize this event.

Dynamic Effects in Stress Analysis for Discrete Elements Modeling: Application to Masonry

2005 ◽  
Author(s):  
Claude Bohatier ◽  
Brahim Chetouane ◽  
Marc Vinches
Keyword(s):  
Stress Tensor ◽  
Relative Weight ◽  
Load Level ◽  
Discrete Element Modelling ◽  
Dynamic Effects ◽  
Discrete Elements ◽  
A Cell ◽  
Definition Of ◽  
Dynamic Excitations ◽  
Final Expression

The discrete element modelling allows the study of the mechanical behaviour of a collection of solids, submitted to dynamic excitations. The proposed definition of a stress tensor concerns a cell constituted of its kernel, and its neighbouring solids. We demonstrate that taking into account the inertial effects allows the symmetry of the stress tensor. The relative weight of the centrifugal effects remaining in the final expression of the stress tensor is evaluated in order to determine whether or not it has to be taken into account, depending on the application. The proposed definition allows the definition of the load level on different parts of the discontinuous structure. Applications to real masonry cases are presented.

scholarly journals An Improved Small-Angle Approximation for Forward Scattering and Its Use in a Fast Two-Component Radiative Transfer Method

2017 ◽  
Vol 74 (6) ◽  
pp. 1959-1987 ◽  
Author(s):  
Bingqiang Sun ◽  
George W. Kattawar ◽  
Ping Yang ◽  
Eli Mlawer
Keyword(s):  
Radiative Transfer ◽  
Small Angle ◽  
Delta Function ◽  
Computational Effort ◽  
Forward Scattering ◽  
Scattering Method ◽  
Diffuse Component ◽  
Dirac Delta ◽  
Small Angle Approximation ◽  
Two Component

Abstract The vector radiative transfer equation is decomposed into two components: a forward component and a diffuse component. The forward component is analytically solved with a small-angle approximation. The solution of the forward component becomes the source for the diffuse component. In the present study, the diffuse component is solved using the successive order of scattering method. The strong anisotropy of the scattering of radiation by a medium is confined to the forward component for which a semianalytical solution is given; consequently, the diffuse component slowly varies as a function of scattering angle once the forward-scattering peak is removed. Moreover, the effect on the diffuse component induced by the forward component can be interpreted by including the low orders of the generalized spherical function expansion of the forward component or even replaced by the Dirac delta function. As a result, the computational effort can be significantly reduced. The present two-component method is validated using the benchmarks related to predefined aerosol and cloud layers with a totally absorbing underlying surface. As a canonical application, the optical properties of water clouds and ice clouds used for the Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 6 cloud-property retrieval products are used for radiative transfer simulations under cloudy conditions.

Economic Class and Access to Physician Services under Public Medical Care Insurance

1973 ◽  
Vol 3 (3) ◽  
pp. 341-355 ◽  
Author(s):  
R. G. Beck
Keyword(s):  
Medical Care ◽  
Low Income ◽  
High Income ◽  
Dynamic Effects ◽  
Physician Services ◽  
Large Sample ◽  
Economic Class ◽  
Definition Of ◽  
Relative Accessibility

The dynamic effects of public medical care insurance on access to physician services are examined in this paper. A special definition of access is employed where access is measured as the inverse of the proportion of families of a given economic class who have not used physician services in a given year. Data are presented for the period 1963 through 1968 for a large sample of families in the Province of Saskatchewan in Canada. The evidence suggests that low-income classes have less contact with physicians than high-income classes. This disparity in accessibility is reduced, but not removed, as experience with Medicare increases. It is concluded that public medical care insurance does result in increased relative accessibility to physicians for the low-income classes.

scholarly journals Solar Disk Center Shows Scattering Polarization in the Sr i 4607 Å Line

2020 ◽  
Vol 893 (2) ◽  
pp. L44
Author(s):  
Franziska Zeuner ◽  
Rafael Manso Sainz ◽  
Alex Feller ◽  
Michiel van Noort ◽  
Sami K. Solanki ◽  
...  
Keyword(s):  
Solar Disk ◽  
Disk Center

scholarly journals Characteristic Length and Time Scales of the Highly Forward Scattering of Photons in Random Media

2019 ◽  
Vol 10 (1) ◽  
pp. 93 ◽  
Author(s):  
Hiroyuki Fujii ◽  
Moegi Ueno ◽  
Kazumichi Kobayashi ◽  
Masao Watanabe
Keyword(s):  
Radiative Transfer ◽  
Time Scales ◽  
Analytical Solutions ◽  
Random Media ◽  
Three Dimensional ◽  
Forward Scattering ◽  
Diffusion Equations ◽  
Transport Models ◽  
Photon Diffusion ◽  
Photon Transport

Background: Elucidation of the highly forward scattering of photons in random media such as biological tissue is crucial for further developments of optical imaging using photon transport models. We evaluated length and time scales of the photon scattering in three-dimensional media. Methods: We employed analytical solutions of the time-dependent radiative transfer, M-th order delta-Eddington, and photon diffusion equations (RTE, dEM, and PDE). We calculated the fluence rates at different source-detector distances and optical properties. Results: We found that the zeroth order dEM and PDE, which approximate the highly forward scattering to the isotropic scattering, are valid in longer length and time scales than approximately 10 / μ t ′ and 40 / μ t ′ v , respectively, where μ t ′ is the reduced transport coefficient and v the speed of light in a medium. The first and second order dEM, which approximate the highly forward-peaked phase function by the first two and three Legendre moments, are valid in the longer scales than approximately 4.0 / μ t ′ and 6.3 / μ t ′ v ; 2.8 / μ t ′ and 3.5 / μ t ′ v , respectively. The boundary conditions less influence the length scales, while they reduce the times scales from those for bulk at the longer length scale than approximately 4.0 / μ t ′ . Conclusion: Our findings are useful for constructions of accurate and efficient photon transport models. We evaluated length and time scales of the highly forward scattering of photons in various kinds of three-dimensional random media by analytical solutions of the radiative transfer, M-th order delta-Eddington, and photon diffusion equations.

Photometric determination of facular contrasts near the solar disk center

1988 ◽  
Vol 324 ◽  
pp. 1184 ◽  
Author(s):  
J. K. Lawrence ◽  
G. A. Chapman ◽  
A. D. Herzog
Keyword(s):  
Solar Disk ◽  
Photometric Determination ◽  
Disk Center
Sign in / Sign up

Export Citation Format

Share Document