scholarly journals Very Long Lived Wave Patterns Detected in the Solar Surface Velocity Signal

2001 ◽  
Vol 560 (1) ◽  
pp. 466-475 ◽  
Author(s):  
Roger K. Ulrich
Keyword(s):  
Solar Surface ◽  
Surface Velocity ◽  
Velocity Signal ◽  
Wave Patterns

Solar surface velocity fields determined from small magnetic features

Solar Physics ◽  
1990 ◽  
Vol 130 (1-2) ◽  
pp. 295-311 ◽  
Author(s):  
R. F. Howard ◽  
J. W. Harvey ◽  
S. Forgach
Keyword(s):  
Solar Surface ◽  
Velocity Fields ◽  
Surface Velocity ◽  
Magnetic Features

scholarly journals Resolving the influence of temperature forcing through heat conduction on rockglacier dynamics: a numerical modelling approach

2018 ◽  
Author(s):  
Alessandro Cicoira ◽  
Jan Beutel ◽  
Jerome Faillettaz ◽  
Isabelle Gärtner-Roer ◽  
Andreas Vieli
Keyword(s):  
Heat Conduction ◽  
Numerical Modelling ◽  
Swiss Alps ◽  
Surface Velocity ◽  
Creep Model ◽  
Model Parameters ◽  
Velocity Signal ◽  
Annual Variability ◽  
Order Of Magnitude ◽  
Modelling Approach

Abstract. In recent years, observations have highlighted seasonal and inter-annual variability in rockglacier flow. Temperature forcing, through heat conduction, has been proposed as one of the key processes to explain these variations in kinematics. However, this mechanism has not yet been quantitatively assessed against real-world data. We present a 1-D numerical modelling approach that couples heat conduction to an empirically derived creep model for ice-rich frozen soils. We use this model to investigate the effect of thermal heat conduction on seasonal and inter-annual variability in rockglacier flow. We compare the model results with borehole temperature data and surface velocity measurements from the PERMOS and PermaSense monitoring network in the Swiss Alps. We further conduct a model sensitivity analysis in order to resolve the importance of the different model parameters. Using the prescribed empirically derived rheology and observed near-surface temperatures, we are able to model the right order of magnitude of creep flow. However, both inter-annual and seasonal variability are underestimated by an order of magnitude, implying that heat conduction alone can not explain the observed variations. Therefore, non-conductive processes, likely linked to water availability, dominate the short-term velocity signal.

scholarly journals Magnetic solar surface flux transport simulation

2019 ◽  
Vol 13 (28) ◽  
pp. 33-43
Author(s):  
Loay K. Abood
Keyword(s):  
Magnetic Flux ◽  
Flux Distribution ◽  
Solar Surface ◽  
Surface Flux ◽  
Surface Velocity ◽  
Advection Equation ◽  
Implicit Methods ◽  
Flux Transport ◽  
Tilted Angle ◽  
Angle Parameter

In this paper, the solar surface magnetic flux transport has been simulated by solving the diffusion–advection equation utilizing numerical explicit and implicit methods in 2Dsurface. The simulation was used to study the effect of bipolar tilted angle on the solar flux distribution with time. The results show that the tilted angle controls the magnetic distribution location on the sun’s surface, especially if we know that the sun’s surface velocity distribution is a dependent location. Therefore, the tilted angle parameter has distribution influence.

Mean field solar surface dynamo in the presence of partially ionized plasmas and sub-surface shear layer

2019 ◽  
Vol 488 (3) ◽  
pp. 4329-4337
Author(s):  
B S Paradkar ◽  
S M Chitre ◽  
V Krishan
Keyword(s):  
Magnetic Field ◽  
Shear Layer ◽  
Solar Surface ◽  
Mean Field ◽  
Ambipolar Diffusion ◽  
Velocity Shear ◽  
Surface Velocity ◽  
Dynamo Model ◽  
Surface Shear ◽  
Partially Ionized

Abstract A non-linear α − Ω dynamo in the partially ionized turbulent plasma in the presence of sub-surface velocity shear is studied with mean-field electrodynamics. Such a dynamo is probably operational in the near-surface region of the Sun, where the presence of both neutrals and the velocity shear (due to sub-surface shear layer in the rotation profile) is observationally well established. In particular, we show that the inclusion of ambipolar diffusion leads to a saturation of magnetic field amplitudes in the α − Ω dynamo. We also demonstrate that the temporal evolution of large-scale global magnetic fields follows the well-known pattern similar to the ‘butterfly’ diagram displayed by sunspots. As usual the velocity shear converts part of the poloidal into the toroidal magnetic field which in turn is regenerated largely by the combined kinetic plus Hall helicity, thus closing the dynamo loop. In addition, by allowing temporal variation in the helicity and ambipolar diffusion coefficient we are able to reproduce the grand-minimum type behaviour of the solar dynamo. Details of theoretical model along with numerical computations of dynamo equations in the partially ionized plasma are outlined. The solar surface dynamo model envisaged in this work could operate in conjunction with the global dynamo present in the bulk of the convection zone.

scholarly journals Are granules good tracers of solar surface velocity fields?

2001 ◽  
Vol 377 (2) ◽  
pp. L14-L17 ◽  
Author(s):  
M. Rieutord ◽  
T. Roudier ◽  
H.-G. Ludwig ◽  
Å. Nordlund ◽  
R. Stein
Keyword(s):  
Solar Surface ◽  
Velocity Fields ◽  
Surface Velocity

Alpha-Effect, Current and Kinetic Helicities for Magnetically Driven Turbulence, and Solar Dynamo

2000 ◽  
Vol 179 ◽  
pp. 387-388
Author(s):  
Gaetano Belvedere ◽  
V. V. Pipin ◽  
G. Rüdiger
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Convection Zone ◽  
Solar Surface ◽  
Momentum Transport ◽  
Angular Momentum Transport ◽  
Magnetic Buoyancy ◽  
Alpha Effect ◽  
Current Helicity

Extended AbstractRecent numerical simulations lead to the result that turbulence is much more magnetically driven than believed. In particular the role ofmagnetic buoyancyappears quite important for the generation ofα-effect and angular momentum transport (Brandenburg & Schmitt 1998). We present results obtained for a turbulence field driven by a (given) Lorentz force in a non-stratified but rotating convection zone. The main result confirms the numerical findings of Brandenburg & Schmitt that in the northern hemisphere theα-effect and the kinetic helicityℋkin= 〈u′ · rotu′〉 are positive (and negative in the northern hemisphere), this being just opposite to what occurs for the current helicityℋcurr= 〈j′ ·B′〉, which is negative in the northern hemisphere (and positive in the southern hemisphere). There has been an increasing number of papers presenting observations of current helicity at the solar surface, all showing that it isnegativein the northern hemisphere and positive in the southern hemisphere (see Rüdigeret al. 2000, also for a review).

Temporal Forcing of Traveling Wave Patterns

1996 ◽  
Vol 6 (11) ◽  
pp. 1417-1434 ◽  
Author(s):  
Joceline Lega ◽  
Jean-Marc Vince
Keyword(s):  
Traveling Wave ◽  
Wave Patterns

Modeling Vibration-Induced Tire-Pavement Interaction Noise in the Mid-frequency Range

2020 ◽  
Author(s):  
Sterling McBride ◽  
Ricardo Burdisso ◽  
Corina Sandu
Keyword(s):  
Sound Intensity ◽  
Element Model ◽  
Dominant Frequency ◽  
Contact Forces ◽  
Surface Velocity ◽  
New Wave ◽  
Normal Surface ◽  
Radiated Noise ◽  
Physical Effects ◽  
Effects Of Rotation

ABSTRACT Tire-pavement interaction noise (TPIN) is one of the main sources of exterior noise produced by vehicles traveling at greater than 50 kph. The dominant frequency content is typically within 500–1500 Hz. Structural tire vibrations are among the principal TPIN mechanisms. In this work, the structure of the tire is modeled and a new wave propagation solution to find its response is proposed. Multiple physical effects are accounted for in the formulation. In an effort to analyze the effects of curvature, a flat plate and a cylindrical shell model are presented. Orthotropic and nonuniform structural properties along the tire's transversal direction are included to account for differences between its sidewalls and belt. Finally, the effects of rotation and inflation pressure are also included in the formulation. Modeled frequency response functions are analyzed and validated. In addition, a new frequency-domain formulation is presented for the computation of input tread pattern contact forces. Finally, the rolling tire's normal surface velocity response is coupled with a boundary element model to demonstrate the radiated noise at the leading and trailing edge locations. These results are then compared with experimental data measured with an on-board sound intensity system.

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