On the Generation of Flux-Tube Waves in Stellar Convection Zones. II. Improved Treatment of Longitudinal Tube Wave Generation

1995 ◽  
Vol 448 ◽  
pp. 865 ◽  
Author(s):  
Z. E. Musielak ◽  
R. Rosner ◽  
H. P. Gail ◽  
P. Ulmschneider
Keyword(s):  
Flux Tube ◽  
Wave Generation ◽  
Stellar Convection ◽  
Tube Wave

On the Generation of Flux‐Tube Waves in Stellar Convection Zones. III. Longitudinal Tube Wave‐Energy Spectra and Fluxes for Late‐Type Stars

2000 ◽  
Vol 541 (1) ◽  
pp. 410-417 ◽  
Author(s):  
Z. E. Musielak ◽  
R. Rosner ◽  
P. Ulmschneider
Keyword(s):  
Flux Tube ◽  
Wave Energy ◽  
Energy Spectra ◽  
Late Type ◽  
Stellar Convection ◽  
Tube Wave

scholarly journals Linking Thin Flux Tube MHD Models to Apparent Stellar Surface Activity

2004 ◽  
Vol 219 ◽  
pp. 546-551
Author(s):  
T. Granzer ◽  
K. G. Strassmeier
Keyword(s):  
Magnetic Flux ◽  
Surface Activity ◽  
Flux Tube ◽  
Convection Zone ◽  
Active Regions ◽  
Similar Model ◽  
Flux Tubes ◽  
Stellar Convection ◽  
Magnetic Flux Tubes ◽  
Spot Formation

We model thin magnetic flux tubes as they rise from the bottom of a stellar convection zone to the photosphere. On emergence they form active regions, i.e. star spots. This model was very successfully applied to the solar case, where the simulations where in agreement with the butterfly diagram, Joy's law, and Hale's law. We propose the use of a similar model to describe stellar activity in the more extreme form found on active stars. A comparison between Doppler-images of well-observed pre-MS stars and a theoretically derived probability of star-spot formation as a function of latitude is presented.

Generation of nonlinear magnetic flux tube wave energies in Procyon A

2019 ◽  
Author(s):  
D E Fawzy ◽  
A T Saygac ◽  
K Stȩpień
Keyword(s):  
Magnetic Flux ◽  
Acoustic Wave ◽  
Flux Tube ◽  
Convection Zone ◽  
Frequency Factor ◽  
Turbulent Energy ◽  
Current Approach ◽  
Magnetic Flux Tube ◽  
Tube Wave ◽  
Wave Modes

Abstract The aim of the current study is the computation of the magnetic flux tube wave energies and fluxes generated in the convection zone of Procyon A. This is a subgiant of spectral type F5 IV-V showing chromospheric and coronal activities. The mechanisms responsible for the generation of different wave modes include the interaction of the thin and vertically oriented magnetic flux tube embedded in magnetic-free regions with turbulence in the convection zone of Procyon A. We are considering longitudinal, transverse and acoustic wave modes. Turbulence in the convection zone is modeled by the extended Kolmogorov turbulent energy spectrum and the modified Gaussian frequency factor. Different magnetic flux tube models with different degrees of magnetic activities were considered. The current approach takes the nonlinear effects into consideration. The results show that there is enough wave energy in the three different forms to heat the outer layers of the star. The obtained acoustic wave energies are larger than those of the longitudinal tube wave energies compared to the solar case. This can be explained by the relatively low magnetic field strength. On the other side, our computations show the importance of the transverse wave energies compared to the energies carried by the longitudinal waves. The former waves carry energy several (between 2 and 14) times higher than the latter. The obtained wave energies are essential for constructing time-dependent model chromospheres and for the predictions of atmospheric oscillations to be compared e.g. with the data collected by the CoRoT and Kepler missions.

On the generation of flux tube waves in stellar convection zones. I - Longitudinal tube waves driven by external turbulence

1989 ◽  
Vol 337 ◽  
pp. 470 ◽  
Author(s):  
Z. E. Musielak ◽  
R. Rosner ◽  
P. Ulmschneider
Keyword(s):  
Flux Tube ◽  
Stellar Convection ◽  
External Turbulence

scholarly journals Tube wave generation at a layer boundary for an incident compressional plane wave

1992 ◽  
Author(s):  
Chengbin Peng ◽  
M. Nafi Toksöz
Keyword(s):  
Plane Wave ◽  
Wave Generation ◽  
Layer Boundary ◽  
Tube Wave

Modeling wave generation by borehole orbital vibrator source

Geophysics ◽  
2006 ◽  
Vol 71 (1) ◽  
pp. F1-F11
Author(s):  
Seiji Nakagawa ◽  
Thomas M. Daley
Keyword(s):  
Shear Wave ◽  
3D Models ◽  
Wave Generation ◽  
Guided Wave ◽  
Wave Radiation ◽  
S Wave ◽  
Wave Source ◽  
Partial Wave Expansion ◽  
Single Well ◽  
Tube Wave

An orbital vibrator source (OVS), a fluid-coupled shear-wave source, has many properties useful for crosswell, single-well, and borehole-to-surface imaging of both P- (compressional) and S- (shear) wave velocities of reservoir rocks. To this day, however, only a limited number of quantitative models have been developed to explain its properties. In this article, we develop both 2D and 3D models of an OVS, allowing us to examine source characteristics such as radiation patterns, frequency dependence of wave amplitudes, and guided-wave generation. These models are developed in the frequency-wavenumber domain using the partial wave expansion of the wavefield within and outside the borehole. The models predict many unique characteristics of an OVS, including formation-property-dependent vibrator amplitudes, uniform isotropic S-wave radiation pattern, and small tube-wave generation.

scholarly journals Hydraulic Properties of Closely Spaced Dipping Open Fractures Intersecting a Fluid-Filled Borehole Derived From Tube Wave Generation and Scattering

2017 ◽  
Vol 122 (10) ◽  
pp. 8003-8020 ◽  
Author(s):  
Shohei Minato ◽  
Ranajit Ghose ◽  
Takeshi Tsuji ◽  
Michiharu Ikeda ◽  
Kozo Onishi
Keyword(s):  
Hydraulic Properties ◽  
Wave Generation ◽  
Open Fractures ◽  
Tube Wave

On the Generation of Flux‐Tube Waves in Stellar Convection Zones. IV. Longitudinal Wave Energy Spectra and Fluxes for Stars with Nonsolar Metallicities

2002 ◽  
Vol 573 (1) ◽  
pp. 418-424 ◽  
Author(s):  
Z. E. Musielak ◽  
R. Rosner ◽  
P. Ulmschneider
Keyword(s):  
Longitudinal Wave ◽  
Flux Tube ◽  
Wave Energy ◽  
Energy Spectra ◽  
Stellar Convection

scholarly journals Fracture compliance estimation using borehole tube waves

Geophysics ◽  
2013 ◽  
Vol 78 (4) ◽  
pp. D249-D260 ◽  
Author(s):  
Sudhish Kumar Bakku ◽  
Michael Fehler ◽  
Daniel Burns
Keyword(s):  
Amplitude Ratio ◽  
Wave Generation ◽  
Transition Frequency ◽  
P Wave ◽  
Fracture Aperture ◽  
Generation Model ◽  
Data Set ◽  
Fracture Properties ◽  
Lateral Extent ◽  
Tube Wave

We tested two models, one for tube-wave generation and the other for tube-wave attenuation at a fracture intersecting a borehole that can be used to estimate fracture compliance, fracture aperture, and lateral extent. In the tube-wave generation model, we consider tube-wave excitation in the borehole when a P-wave is incident on the fracture. The amplitude ratio of the pressure due to the tube wave to that of the incident P-wave is a function of fracture compliance, aperture, and length. Similarly, the attenuation of a tube wave in the borehole as it crosses a fracture intersecting the borehole is also a function of fracture properties. Numerically solving the dispersion relation in the fracture, we study tube-wave generation and the attenuation coefficient as a function of frequency. We observed that measuring amplitude ratios or attenuation near a transition frequency can help constrain the fracture properties. The transition frequency corresponds to the regime in which the viscous skin depth in the fracture is comparable to its aperture. Measurements in the high-frequency limit can place a lower bound on fracture compliance and lateral extent. We evaluated the applicability of the tube-wave generation model to a previously published VSP data set and found that compliance values of the order [Formula: see text]–[Formula: see text] are likely in the field. These observations support scaling of fracture compliance with fracture size.

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