Geoeffective Properties of Solar Transients and Stream Interaction Regions

Abstract Examination of the temporal variability properties of several strong optical recombination lines in a large sample of Galactic Wolf–Rayet (WR) stars reveals possible trends, especially in the more homogeneous WC than the diverse WN subtypes, of increasing wind variability with cooler subtypes. This could imply that a serious contender for the driver of the variations is stochastic, magnetic subsurface convection associated with the 170 kK partial-ionization zone of iron, which should occupy a deeper and larger zone of greater mass in cooler WR subtypes. This empirical evidence suggests that the heretofore proposed ubiquitous driver of wind variability, radiative instabilities, may not be the only mechanism playing a role in the stochastic multiple small-scaled structures seen in the winds of hot luminous stars. In addition to small-scale stochastic behaviour, subsurface convection guided by a global magnetic field with localized emerging loops may also be at the origin of the large-scale corotating interaction regions as seen frequently in O stars and occasionally in the winds of their descendant WR stars.

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Muon and neutron observations in connection with the corotating interaction regions

Advances in Space Research ◽

10.1016/j.asr.2006.12.013 ◽

2007 ◽

Vol 40 (3) ◽

pp. 348-352 ◽

Cited By ~ 3

Author(s):

M.R. Da Silva ◽

A. Dal Lago ◽

E. Echer ◽

A. de Lucas ◽

W.D. Gonzalez ◽

...

Keyword(s):

Corotating Interaction Regions ◽

Interaction Regions

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Comparison of Inviscid Computations With Theory and Experiment in Vibrating Transonic Compressor Cascades

Volume 1: Turbomachinery ◽

10.1115/90-gt-373 ◽

1990 ◽

Cited By ~ 3

Author(s):

G. A. Gerolymos ◽

E. Blin ◽

H. Quiniou

Keyword(s):

Boundary Layer ◽

Plate Theory ◽

Strong Shock ◽

Acoustic Resonance ◽

Boundary Layer Separation ◽

Computational Method ◽

Viscous Effects ◽

Transonic Compressor ◽

Boundary Layer Interaction ◽

Interaction Regions

The prediction of unsteady flow in vibrating transonic cascades is essential in assessing the aeroelastic stability of fans and compressors. In the present work an existing computational code, based on the numerical integration of the unsteady Euler equations, in blade-to-blade surface formulation, is validated by comparison with available theoretical and experimental results. Comparison with the flat plate theory of Verdon is, globally, satisfactory. Nevertheless, the computational results do not exhibit any particular behaviour at acoustic resonance. The use of a 1-D nonreflecting boundary condition does not significantly alter the results. Comparison of the computational method with experimental data from started and unstarted supersonic flows, with strong shock waves, reveals that, notwithstanding the globally satisfactory performance of the method, viscous effects are prominent at the shock wave/boundary layer interaction regions, where boundary layer separation introduces a pressure harmonic phase shift, which is not presicted by inviscid methods.

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Analytical treatment of two-dimensional supersonic flow. II. Flow with weak shocks

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1956.0007 ◽

1956 ◽

Vol 248 (952) ◽

pp. 499-515 ◽

Cited By ~ 6

Keyword(s):

Solution Process ◽

Wave Interaction ◽

Analytical Treatment ◽

Plane Flow ◽

Flow Equations ◽

Interaction Regions ◽

Steady Plane ◽

Set Up ◽

Downstream Flow ◽

Weak Shocks

A scheme of approximate solution is presented for the treatment of shock waves in the steady, plane flow of a perfect gas. It is based on the neglect of any entropy variations produced by the shocks and hence is applicable only when the shocks are weak. The method provides an extension of Friedrichs’s (1948) results for simple waves to wave-interaction regions. By an examination of the solution of the continuous-flow equations in the neighbourhood of a known shock wave it is shown how the downstream flow may be calculated without reference to the particular shock shape (§2). There are certain cases in which this approach fails and they are discussed by means of a typical example in §3.3. Once the downstream flow has been calculated, it is possible to set up general equations for the determination of the shock (§ 2). Examples of the solution of these equations for typical problems are given in §3. In §4 there is a brief discussion of the validity of using homentropic theory and estimates of the errors involved in the solution process are obtained.

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