scholarly journals Nonlinear gyrokinetic PIC simulations in stellarators with the code EUTERPE

2020 ◽  
Vol 86 (5) ◽  
Author(s):  
E. Sánchez ◽  
A. Mishchenko ◽  
J. M. García-Regaña ◽  
R. Kleiber ◽  
A. Bottino ◽  
...  
Keyword(s):  
Linear Growth ◽  
Collision Operator ◽  
Zonal Flow ◽  
Linear Growth Rate ◽  
Plasma Parameters ◽  
Particle In Cell ◽  
Nonlinear Simulations ◽  
Flow Evolution ◽  
Linear And Nonlinear

In this work, the first nonlinear particle-in-cell simulations carried out in a stellarator with the global gyrokinetic code EUTERPE using adiabatic electrons and realistic plasma parameters are reported. Several studies are conducted with the aim of enabling reliable nonlinear simulations in stellarators with this code. First, EUTERPE is benchmarked against ORB5 in both linear and nonlinear settings in a tokamak configuration. Next, the use of noise control and stabilization tools, a Krook-type collision operator, markers’ weight smoothing and heating sources is investigated. It is studied in detail how these tools influence the linear growth rate of instabilities in both tokamak and stellarator geometries, and their influence on the linear zonal flow evolution in a stellarator. Then, it is studied how these tools allow improvement of the quality of the results in a set of nonlinear simulations of electrostatic turbulence in a stellarator configuration. Finally, these tools are applied to a W7-X magnetic configuration using experimental plasma parameters.

Dynamics of ultra-thin two-layer films under the action of inclined temperature gradients

2009 ◽  
Vol 631 ◽  
pp. 165-197 ◽  
Author(s):  
ALEXANDER A. NEPOMNYASHCHY ◽  
ILYA B. SIMANOVSKII
Keyword(s):  
Growth Rate ◽  
Temperature Gradient ◽  
Linear Growth ◽  
Nonlinear Evolution ◽  
Temperature Gradients ◽  
Linear Stability Theory ◽  
Linear Growth Rate ◽  
Nonlinear Simulations ◽  
Inclined Temperature Gradient ◽  
Longitudinal Structures

The development of instabilities under the joint action of the van der Waals forces and Marangoni stresses in a two-layer film in the presence of an inclined temperature gradient is investigated. The problem is solved by means of a linear stability theory and nonlinear simulations. It has been found that for sufficiently large values of the ratio between the longitudinal and transverse Marangoni numbers, the real part of the linear growth rate does not depend on the direction of the wavenumber, except the case of nearly longitudinal disturbances. Numerous types of nonlinear evolution have been observed, among them are ordered systems of droplets, ‘splashes’, oblique waves, modulated transverse and longitudinal structures.

Microborings and growth in Late Ordovician halysitids and other corals

1993 ◽  
Vol 67 (6) ◽  
pp. 922-934 ◽  
Author(s):  
Robert J. Elias ◽  
Dong-Jin Lee
Keyword(s):  
Growth Rate ◽  
Linear Growth ◽  
Inverse Correlation ◽  
Weight Percent ◽  
Late Ordovician ◽  
Coral Growth ◽  
Linear Growth Rate ◽  
Skeletal Density ◽  
Rugose Coral ◽  
Endolithic Algae

Microborings in the Late Ordovician tabulate corals Catenipora rubra (a halysitid) and Manipora amicarum (a cateniform nonhalysitid) and in an epizoic solitary rugose coral differ from nearly all of those previously reported in Paleozoic corals. These microborings were formed within the coralla by endolithic algae and fungi located beneath living polyps. Comparable structures in the Late Ordovician tabulate Quepora ?agglomeratiformis (a halysitid) represent algal microborings, not spicules, and halysitids are corals, not sponges as suggested by Kaźmierczak (1989).Endolithic algae in cateniform tabulates relied primarily on light entering through the outer walls of the ranks rather than through the polyps; lacunae within coralla permitted appropriate levels of light to reach many corallites. The direction of boring was determined by corallum microstructure and possibly also by the distribution of organic matter within the skeleton. There is an apparent inverse correlation between boring activity and coral growth rate.The location and relative abundance of pyritized microborings within calcareous coralla can be established quantitatively and objectively from electron microprobe determinations of weight percent sulfur along appropriate traverses of the coral skeleton. The distribution of such microborings in Catenipora rubra and Manipora amicarum is comparable to algal banding in modern corals; this is the first report of such banding in the interiors of Paleozoic corals. Change in the intensity of boring within each corallum was evidently a response to variation in the linear growth rate of the coral, or to fluctuation in an environmental factor (perhaps light intensity) that could control both algal activity and growth rate in these corals. Change in the algal boring intensity and linear growth rate of the coral was generally but not always seasonal and usually but not invariably associated with change in the density of coral skeletal deposition.Cyclic bands of boring abundance maxima within fossil colonial corals provide a measure of annual linear growth comparable to the widely accepted method based on skeletal density bands. Algal bands are more sporadically developed than density bands within and among coralla, thus increasing the difficulty of interpretation. Fluctuations in the abundance of algal microborings apparently provide a detailed record of changes in the linear growth rate of colonies and of individuals within colonies. Combined analyses of microboring abundance and skeletal density will contribute significantly to our understanding of the biological and environmental factors involved in endolithic activity and coral growth.

A linear and quasi-linear investigation of the crossfield current-driven ion-acoustic instability

1982 ◽  
Vol 28 (2) ◽  
pp. 267-279 ◽  
Author(s):  
R. Bharuthram ◽  
M. A. Hellberg
Keyword(s):  
Linear Growth ◽  
Velocity Distribution Function ◽  
Linear Growth Rate ◽  
Particle Diffusion ◽  
Anomalous Resistivity ◽  
Heating Rates ◽  
Ion Heating ◽  
Acoustic Instability ◽  
Ion Acoustic ◽  
Drift Instability

The linear growth rate of the crossfield current-driven ion-acoustic instability is obtained for any equilibrium particle velocity distribution function of the type . Quasi-linear theory is then used to investigate the saturation of the instability. Several associated features, namely, particle diffusion in velocity space, anomalous resistivity, energy distribution and electron and ion heating rates are evaluated for a Maxwellian distribution. Finally, a brief comparison is made with the heating rates associated with the electron cyclotron drift instability.

scholarly journals <sup>210</sup>Pb-<sup>226</sup>Ra chronology reveals rapid growth rate of <i>Madrepora oculata</I> and <i>Lophelia pertusa</i> on world's largest cold-water coral reef

2011 ◽  
Vol 8 (6) ◽  
pp. 12247-12283
Author(s):  
P. Sabatier ◽  
J.-L. Reyss ◽  
J. M. Hall-Spencer ◽  
C. Colin ◽  
N. Frank ◽  
...  
Keyword(s):  
Growth Rate ◽  
Coral Reef ◽  
Linear Growth ◽  
Cold Water ◽  
Optimal Growth ◽  
Growth Conditions ◽  
Age And Growth ◽  
Linear Growth Rate ◽  
Lophelia Pertusa ◽  
Water Coral

Abstract. Here we show the use of the 210Pb-226Ra excess method to determine the growth rate of corals from one of the world's largest known cold-water coral reef, the Røst Reef off Norway. Two large branching framework-forming cold-water coral specimens, one Lophelia pertusa and one Madrepora oculata were collected alive at 350 m water depth from the Røst Reef at ~67° N and ~9° E. Pb and Ra isotopes were measured along the major growth axis of both specimens using low level alpha and gamma spectrometry and the corals trace element compositions were studied using ICP-QMS. Due to the different chemical behaviors of Pb and Ra in the marine environment, 210Pb and 226Ra were not incorporated the same way into the aragonite skeleton of those two cold-water corals. Thus to assess of the growth rates of both specimens we have here taken in consideration the exponential decrease of initially incorporated 210Pb as well as the ingrowth of 210Pb from the decay of 226Ra. Moreover a~post-depositional 210Pb incorporation is found in relation to the Mn-Fe coatings that could not be entirely removed from the oldest parts of the skeletons. The 226Ra activities in both corals were fairly constant, then assuming constant uptake of 210Pb through time the 210Pb-226Ra chronology can be applied to calculate linear growth rate. The 45.5 cm long branch of M. oculata reveals an age of 31 yr and a~linear growth rate of 14.4 ± 1.1 mm yr−1, i.e. 2.6 polyps per year. However, a correction regarding a remaining post-depositional Mn-Fe oxide coating is needed for the base of the specimen. The corrected age tend to confirm the radiocarbon derived basal age of 40 yr (using 14C bomb peak) with a mean growth rate of 2 polyps yr−1. This rate is similar to the one obtained in Aquaria experiments under optimal growth conditions. For the 80 cm-long specimen of L. pertusa a remaining contamination of metal-oxides is observed for the middle and basal part of the coral skeleton, inhibiting similar accurate age and growth rate estimates. However, the youngest branch was free of Mn enrichment and this 15 cm section reveals a growth rate of 8 mm yr−1 (~1 polyp every two to three years). However, the 210Pb growth rate estimate is within the lowermost ranges of previous growth rate estimates and may thus reflect that the coral was not developing at optimal growth conditions. Overall, 210Pb-226Ra dating can be successfully applied to determine the age and growth rate of framework-forming cold-water corals, however, removal of post-depositional Mn-Fe oxide deposits is a prerequisite. If successful, large branching M. oculata and L. pertusa coral skeletons provide unique oceanographic archive for studies of intermediate water environmentals with an up to annual time resolution and spanning over many decades.

scholarly journals Effect of the electron redistribution on the nonlinear saturation of Alfvén eigenmodes and the excitation of zonal flows

2020 ◽  
Vol 86 (3) ◽  
Author(s):  
A. Biancalani ◽  
A. Bottino ◽  
P. Lauber ◽  
A. Mishchenko ◽  
F. Vannini
Keyword(s):  
Magnetic Field ◽  
Zonal Flow ◽  
Large Aspect Ratio ◽  
Nonlinear Saturation ◽  
Energetic Ions ◽  
Electron Population ◽  
Zonal Flows ◽  
Particle In Cell ◽  
Alfven Eigenmodes ◽  
Reversed Shear

Numerical simulations of Alfvén modes driven by energetic particles are performed with the gyrokinetic (GK) global particle-in-cell code ORB5. A reversed shear equilibrium magnetic field is adopted. A simplified configuration with circular flux surfaces and large aspect ratio is considered. The nonlinear saturation of beta-induced Alfvén eigenmodes (BAE) is investigated. The roles of the wave–particle nonlinearity of the different species, i.e. thermal ions, electrons and energetic ions are described, in particular for their role in the saturation of the BAE and the generation of zonal flows. The nonlinear redistribution of the electron population is found to be important in increasing the BAE saturation level and the zonal flow amplitude.

scholarly journals Generation of Wave Groups by Shear Layer Instability

Fluids ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 39 ◽  
Author(s):  
Roger Grimshaw
Keyword(s):  
Growth Rate ◽  
Group Velocity ◽  
Linear Growth ◽  
Linear Stability Theory ◽  
Linear Growth Rate ◽  
Wave Groups ◽  
Weakly Nonlinear ◽  
Complex Valued ◽  
Fundamental Requirement ◽  
Temporal Growth Rate

The linear stability theory of wind-wave generation is revisited with an emphasis on the generation of wave groups. The outcome is the fundamental requirement that the group move with a real-valued group velocity. This implies that both the wave frequency and the wavenumber should be complex-valued, and in turn this then leads to a growth rate in the reference frame moving with the group velocity which is in general different from the temporal growth rate. In the weakly nonlinear regime, the amplitude envelope of the wave group is governed by a forced nonlinear Schrödinger equation. The effect of the wind forcing term is to enhance modulation instability both in terms of the wave growth and in terms of the domain of instability in the modulation wavenumber space. Also, the soliton solution for the wave envelope grows in amplitude at twice the linear growth rate.

scholarly journals Effect of fungicides on the growth of fungi isolated from in vitro propagated fruit-bearing plants

2017 ◽  
Vol 38 (SI 2 - 6th Conf EFPP 2002) ◽  
pp. 329-331
Author(s):  
M. Kowalik ◽  
M. Gródek
Keyword(s):  
In Vitro Propagation ◽  
Linear Growth ◽  
Linear Growth Rate ◽  
Ms Medium ◽  
Penicillium Verrucosum ◽  
Mortierella Isabellina ◽  
Cladosporium Sphaerospermum ◽  
Murashige Skoog ◽  
Growth Of Fungi

The aim of the work was to determine the effect of fungicides: Topsin M 70 WG, Bravo 500 SC, and Sportak 45 EC in two concentrations on the growth of fungi: Aspergillus niger, Epicoccum purpurascens, Cladosporium sphaerospermum, Mortierella isabellina and Penicillium verrucosum var. verrucosum on PDA and Murashige-Skoog medium (MS). The smallest index of linear growth rate of the fungi had Topsin M 70 WG for fungi: E. purpurascens and P. verrucosum var. verrucosum on PDA and MS medium and for M. isabellina and C. sphaerospermum on MS in concentrations of 71.42 mg/l and 107.13 mg/l. The highest index of linear growth had Bravo 500 SC in concentrations of 0.5 ml/l and 0.75 ml/l on PDA for E. purpurascens and A. niger. The lowest index of linear growth on MS for E. purpurascens, C. sphaerospermum and P. verrucosum var. verrucosum was noted down. The highest effectiveness in control of linear growth all tested species of fungi was found for fungicide Sportak 45 EC in concentration of 0.55 ml/l and 0.825 ml/l on MS and PDA. Among all tested fungicides used in vitro propagation fungicides from imidazoles group are recommended.

scholarly journals Wavelength dependence of the linear growth rate of the <I>E<sub>s</sub></I> layer instability

2007 ◽  
Vol 25 (6) ◽  
pp. 1311-1322 ◽  
Author(s):  
R. B. Cosgrove
Keyword(s):  
Growth Rate ◽  
Electric Fields ◽  
Large Scale ◽  
Linear Growth ◽  
Three Dimensional ◽  
Generalized Derivation ◽  
Wavelength Dependence ◽  
Meridional Wind ◽  
Linear Growth Rate ◽  
Significant Wavelength

Abstract. It has recently been shown, by computation of the linear growth rate, that midlatitude sporadic-E (Es) layers are subject to a large scale electrodynamic instability. This instability is a logical candidate to explain certain frontal structuring events, and polarization electric fields, which have been observed in Es layers by ionosondes, by coherent scatter radars, and by rockets. However, the original growth rate derivation assumed an infinitely thin Es layer, and therefore did not address the short wavelength cutoff. Also, the same derivation ignored the effects of F region loading, which is a significant wavelength dependent effect. Herein is given a generalized derivation that remedies both these short comings, and thereby allows a computation of the wavelength dependence of the linear growth rate, as well as computations of various threshold conditions. The wavelength dependence of the linear growth rate is compared with observed periodicities, and the role of the zeroth order meridional wind is explored. A three-dimensional paper model is used to explain the instability geometry, which has been defined formally in previous works.

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