scholarly journals Fast Solar Flare Proton Acceleration by MHD Turbulence

1990 ◽  
Vol 142 ◽  
pp. 375-382
Author(s):  
Dean. F. Smith
Keyword(s):  
Nonlinear Wave ◽  
Wave Spectrum ◽  
Wave Interaction ◽  
Impulsive Behavior ◽  
Mhd Turbulence ◽  
Wave Interactions ◽  
Proton Acceleration ◽  
Large Wave ◽  
M Wave ◽  
Wave Distribution

Proton acceleration by short-wavelength Alfven (A) waves resonant at the first harmonic of the proton gyrofrequency is reconsidered, taking into account nonlinear wave-wave interactions, collisionless wave losses, and wave escape losses in the geometry of a model coronal loop. It is shown that for the A wave levels required for acceleration in the transrelativistic regime in the 1982 June 3 flare and for acceleration in the nonrelativistic regime in the 1980 June 7 flare, the nonlinear wave interaction of scattering on the polarization clouds of ions will be important. This interaction rapidly isotropizes the A waves which divide their energy with fast magnetosonic (M) waves with a negligible change in their frequency spectrum. Because of electron Landau damping and escape losses, the M waves are confined to two narrow cones about the magnetic field and the total (A+M) wave distribution is still highly anisotropic. The total (A+M) wave spectrum has the same acceleration efficiency as a pure A wave spectrum. There are two principal problems with models of this type. The first is that a large wave energy density is required in a fairly narrow range in k-space. The second is that the protons are effectively bottled up. This makes very impulsive behavior as in the 7 June 1980 flare difficult to explain because proton precipitation is relatively slow.

A transport-equation description of nonlinear ocean surface wave interactions

1975 ◽  
Vol 70 (4) ◽  
pp. 815-826 ◽  
Author(s):  
Kenneth M. Watson ◽  
Bruce J. West
Keyword(s):  
Surface Wave ◽  
Transport Equation ◽  
Energy Transport ◽  
Wave Spectrum ◽  
Interaction Mechanism ◽  
Wave Interaction ◽  
Ocean Current ◽  
Wave Interactions ◽  
Ocean Surface Wave ◽  
Wind Source

The evolution of the power spectrum of surface gravity waves is described by means of an energy transport equation. A slowly varying, prescribed ocean current and wind source are assumed to account for spatial inhomogeneities in the surface wave spectrum. These inhomogeneities lead to a new nonlinear wave-wave interaction mechanism.

scholarly journals WAVES IN TURNING WIND FIELDS

1988 ◽  
Vol 1 (21) ◽  
pp. 43 ◽  
Author(s):  
G.Ph. Van Vledder ◽  
L.H. Holthuijsen
Keyword(s):  
Nonlinear Wave ◽  
Wind Direction ◽  
Wave Spectrum ◽  
Wind Generation ◽  
Wave Direction ◽  
Wind Fields ◽  
Wave Interactions ◽  
The Mean ◽  
High Degree ◽  
Initial Peak

A numerical model to compute to a high degree of accuracy nonlinear wave-wave interactions of wind generated waves supplemented with formulations of wind generation and white-capping, has been used to estimate qualitatively and quantitatively the effect of these physical processes on the directional response of waves in a turning wind field. After a sudden shift in wind direction the wave spectrum develops a secondary peak in the new wind direction. The initial peak of the spectrum either merges fairly quickly with this new peak or it slowly disappears, depending on the magnitude of the directional wind shift. The turning of the mean wave direction towards the new wind direction is caused by wind generation. The processes of nonlinear wave-wave interactions and white-capping tend to slow down the turning rate induced by the wind generation. The net turning rate of the mean wave direction in the model is twice as slow as in observations acquired in the central and southern North Sea.

Hunting for Rogue Waves in a Three-Dimensional Nonlinear Wavefield: A Direct Simulation-Based Approach

2009 ◽  
Author(s):  
Wenting Xiao ◽  
Yuming Liu ◽  
Dick K. P. Yue
Keyword(s):  
Nonlinear Wave ◽  
Rogue Wave ◽  
Wave Spectrum ◽  
Three Dimensional ◽  
Rogue Waves ◽  
High Order ◽  
Wave Steepness ◽  
Large Wave ◽  
Resonant Interactions ◽  
Wavefield Simulation

We describe an investigation of the occurrence, statistics, and generation mechanisms of rogue wave in the open sea using direct three-dimensional phase-resolved nonlinear wavefield simulations. To achieve this we develop an efficient nonlinear wavefield simulation capability based on the high-order spectrum method which solves the primitive phase-resolved Euler equations. The simulations account for nonlinear wave-wave interactions up to an arbitrary high order in the wave steepness and are capable of accounting for effects of bottom bathymetry, variable current, and direct physics-based models for wind input and wave breaking dissipation. We apply direct large-scale simulations to obtain a large number of phase-resolved nonlinear wavefields, initially specified by directional wave spectra. The typical spatial-temporal domain size of such numerical nonlinear wavefields is O(103 km2) over evolution time of O(hr). These spatial and temporal scales account for quartet resonant interactions and partially for quintet resonant interactions among wave components in the wavefield. From the simulated nonlinear wavefields, rogue wave events are identified and their occurrence statistics are studied. It is shown that the classic linear theory (i.e. Rayleigh distribution) significantly underestimates the rogue wave occurrence. Second-order theory improves the Rayleigh prediction, but still underestimates the rogue wave occurrence in wavefields with moderately large wave steepness and relatively narrow directional spreading and spectrum bandwidth. The influence of key wave spectrum parameters (such as significant wave height, directional spreading, effective steepness, and spectrum bandwidth) on the rogue wave occurrence is analyzed. The classification of rogue waves according to their configuration is also obtained. The key characteristics of a rogue wave or rogue wave group in terms of kinematics and surface structure are analyzed and quantified. The nonlinear wave simulations, which provide full three-dimensional kinematics and dynamics of rogue wave events, provide a powerful tool for understanding the underlying mechanisms of their generation. They are elucidated by specific examples.

scholarly journals Operability Guidelines For Product Tanker In Heavy Weather In The Adriatic Sea

2014 ◽  
Vol 21 (1) ◽  
pp. 95-106
Author(s):  
Luka Mudronja ◽  
Marko Katalinić ◽  
Rino Bošnjak ◽  
Pero Vidan ◽  
Joško Parunov
Keyword(s):  
Wave Height ◽  
Adriatic Sea ◽  
Wave Spectrum ◽  
Extreme Weather ◽  
The South ◽  
Sea State ◽  
M Wave ◽  
The North ◽  
Limiting Values ◽  
Deck Wetness

AbstractThis paper presents operability guidelines for seafarers on a product tanker which navigates in the Adriatic Sea during heavy weather. Tanker route starts from the Otranto strait in the south to the island Krk in the north of Adriatic Sea. Heavy weather is caused by south wind called jugo (blowing from E-SE to SS-E, sirocco family). Operability guidelines are given based on an operability criteria platform for presenting ship seakeeping characteristics. Operability criteria considered in this paper are propeller emergence, deck wetness and bow acceleration of a product tanker. Limiting values of mentioned criteria determine sustainable speed. Heavy weather is described by extreme sea state of 7.5 m wave height. Wave spectrum used in this paper is Tabain spectrum which is developed specifically for Adriatic Sea. Seafarer's approach of decisions making in extreme weather is also shown and servers as a guideline for further research of the authors.

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