scholarly journals Stellar Flares: Observations and Theory

1989 ◽  
Vol 104 (2) ◽  
pp. 49-52
Author(s):  
Suzanne L. Hawley
Keyword(s):  
Scaling Law ◽  
Dynamic Scaling ◽  
X Ray ◽  
Temperature Distributions ◽  
Photometric And Spectroscopic Observations ◽  
Stellar Flares ◽  
Consistent Model ◽  
Self Consistent ◽  
Flare Model ◽  
Large Flare

AbstractPhotometric and spectroscopic observations of a very large flare on AD Leo are presented. A self consistent model of a flare corona, transition region and chromosphere is developed; in particular the chromospheric temperature distributions resulting from X-ray and EUV irradiation by coronae of various temperatures are determined. The predicted line fluxes in Hγ are compared to the observed line fluxes to find the coronal temperature as a function of time during the flare. This run of temperature with time is then compared with the predictions of an independent theoretical flare model based on a dynamic scaling law (see paper by Fisher and Hawley, these proceedings).

scholarly journals Determining Ti-17 β-Phase Single-Crystal Elasticity Constants through X-Ray Diffraction and Inverse Scale Transition Model

2011 ◽  
Vol 681 ◽  
pp. 97-102 ◽  
Author(s):  
Sylvain Fréour ◽  
Emmanuel Lacoste ◽  
Manuel François ◽  
Ronald Guillén
Keyword(s):  
Mechanical Load ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Consistent Model ◽  
Self Consistent ◽  
Diffraction Lattice ◽  
Two Phases ◽  
Multi Phase

The scope of this work is the determination of single-crystals elastic constants (SEC) from X-ray diffraction lattice strains measurements performed on multi-phase polycrystals submitted to mechanical load through a bending device. An explicit three scales inverse self-consistent model is developed in order to express the SEC of a cubic phase, embedded in a multi-phase polycrystal, as a function of its X-ray Elasticity Constants. Finally, it is applied to a two-phases (α+β) titanium based alloy (Ti-17), in order to estimate Ti-17 β-phase unknown SEC. The purpose of the present work is to account the proper microstructure of the material. In particular, the morphologic texture of Ti-17 a-phase, i.e. the relative disorientation of the needle-shaped grains constituting this phase, is considered owing to the so-called Generalized Self-Consistent model.

scholarly journals Stellar flare diagnostics from multi–wavelength observations

2009 ◽  
Vol 5 (S264) ◽  
pp. 288-291 ◽  
Author(s):  
Alexander V. Stepanov ◽  
Yuri T. Tsap ◽  
Yulia G. Kopylova
Keyword(s):  
Scaling Law ◽  
Electric Circuit ◽  
Plasma Parameters ◽  
Stellar Flare ◽  
Flare Loop ◽  
X Ray ◽  
Stellar Flares ◽  
Flare Loops ◽  
Red Dwarfs ◽  
Multi Wavelength

AbstractQuasi–periodic pulsations in various wavebands are natural manifestations of emission of stellar flares. We suggest a diagnostic tool of stellar flares based on the coronal seismology and the solar–stellar analogy. Two approaches are used: (I) flare loop as a resonator for MHD oscillations and (II) flare loop as an equivalent electric circuit. Using optical, X–ray, and radio data we obtained flare plasma parameters for the red dwarfs EQ Peg, AT Mic, and AD Leo. The characteristic length of stellar flare loops l ~ R* and their electric currents turned out to be one–two orders of magnitude lager than the solar ones. Advantages of proposed diagnostics in comparison to the scaling law methods are given.

A self-consistent model for line trapping effect in x-ray lasers

1995 ◽  
Author(s):  
Djamel E. Benredjem ◽  
Alain Sureau ◽  
Clary Möller ◽  
Hélène Guennou
Keyword(s):  
X Ray ◽  
Trapping Effect ◽  
Consistent Model ◽  
Self Consistent

scholarly journals Effect of Interlamellar Spacing on the Monotonic Behavior of C70 Pearlitic Steel

2014 ◽  
Vol 996 ◽  
pp. 88-93
Author(s):  
Houda Yahyaoui ◽  
Habib Sidhom ◽  
Chedly Braham ◽  
Andrzej Baczmański ◽  
Manuel François ◽  
...  
Keyword(s):  
Plastic Anisotropy ◽  
Critical Shear Stress ◽  
Interlamellar Spacing ◽  
Pearlitic Steel ◽  
Shear Stresses ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lattice Strains ◽  
Consistent Model ◽  
Self Consistent

The effect of interlamellar spacing on monotonic behavior of C70 pearlitic steel was investigated. Tensile tests under X-ray diffraction coupled with self-consistent model have been used to identify the role of interlamellar spacing on the ferrite plasticity parameters and residual stresses. It has been established that yielding of pearlite is controlled by ferrite critical shear stresses ( τc 0α) which is higher for the smaller interlamellar spacing. Moreover, the residual stress level in ferrite is higher for the largest interlamellar spacing under the same imposed total strain. Lattice strains, measured by synchrotron X-ray diffraction, show an elastic and plastic anisotropy of ferrite crystallites and high stresses in cementite which confirm the self-consistent model calculation. Keywords: Pearlitic steel, X-ray diffraction, Synchrotron radiation, Self-consistent model, Critical shear stress, Lattice strains.

Study of Micromechanical Behaviour of Two Phase Polycrystalline Materials Using Diffraction and Self Consistent Model

2014 ◽  
Vol 783-786 ◽  
pp. 2059-2064
Author(s):  
Andrzej Baczmański ◽  
Elżbieta Gadalińska ◽  
Chedly Braham ◽  
Sebastian Wroński ◽  
Lea le Joncour ◽  
...  
Keyword(s):  
Lattice Strain ◽  
Polycrystalline Materials ◽  
X Ray Diffraction ◽  
Two Phase ◽  
X Ray ◽  
Consistent Model ◽  
Self Consistent ◽  
In Situ Deformation ◽  
Specific Orientation

Diffraction methods for lattice strain measurement provide useful information concerning the nature of grains behaviour during elastoplastic deformation. The main advantage of the diffraction methods is the possibility of studying mechanical properties of polycrystalline materials separately in each phase and in groups of grains with a specific orientation. In this work we present application of the neutron and X-ray diffraction to study “in situ” deformation of two phase stainless steels during tensile loading. The experimental results are compared with self-consistent model.

scholarly journals Characterization of X-ray flare properties of AB Dor

2015 ◽  
Vol 11 (S320) ◽  
pp. 155-160
Author(s):  
S. Lalitha
Keyword(s):  
Scaling Law ◽  
Emission Measure ◽  
The Sun ◽  
Low Mass Stars ◽  
X Ray ◽  
Low Mass ◽  
The Relationship ◽  
Peak Emission ◽  
Large Flare

AbstractThe strong similarities between the flares observed on the Sun and in low mass stars has raised question regarding dynamo in these stars. Using the Sun as a prototype, one may be able to address this. In this paper, we present an analysis of 30 intense X-ray flares observed from AB Dor. These flares detected in XMM-Newton data show a rapid rise (500-3000 s) and a slow decay (1000-6000 s). Our studies suggest that the scaling law between the flare peak emission measure and the flare peak temperature for all the flares observed on AB Dor is very similar to the relationship followed by solar flares. Furthermore, we obtain the frequency distribution of flare energies which is a crucial diagnostic to calculate the overall energy residing in a flare. Our results of this study indicate that the large flare (1033 ≤ E ≤ 1034 erg) may not contribute to the heating of the corona.

scholarly journals Constraints of Winds from Accretion Disks

1997 ◽  
Vol 163 ◽  
pp. 475-480
Author(s):  
I. Idan ◽  
G. Shaviv
Keyword(s):  
Critical Point ◽  
Accretion Disk ◽  
Accretion Disks ◽  
Narrow Range ◽  
X Rays ◽  
X Ray ◽  
Consistent Model ◽  
Self Consistent

AbstractThe structure of an accretion disk illuminated by X-rays is investigated. For high values of X-ray heating no static disk solution was found, while for low values of heating a corona was formed above the disk. In the high X-ray illumination case the only possible wind solution is the supersonic solution meaning the evaporation of the disk. Only a very narrow range of X- ray heating and critical point height yield the proper wind solution that agrees with the disk solution. Finally, a self-consistent model of accretion disk and a wind is presented.

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