Growth rate evaluation for the decay instability in space plasmas

2020 ◽  
Author(s):  
Horia Comisel ◽  
Yasuhito Narita ◽  
Uwe Motschmann
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Alfven Wave ◽  
Wave Coupling ◽  
Decay Instability ◽  
Field Fluctuations ◽  
Density Perturbations ◽  
Rate Evaluation ◽  
First Time ◽  
Hall Mhd

<p><tt class="letterText">Here we evaluate for the first time the growth rate of the decay instability in the 2-D wavevector domain spanning the parallel and perpendicular directions to the mean magnetic field. The growth rate is computed for the density perturbations based on the Hall MHD wave-wave coupling theory, which serves as a proxy for the energy spectrum of the compressive magnetic field fluctuations. The growth rate is then also determined for the daughter waves by considering the conservation of the frequencies and the wavevectors for the wave transmission (additive wave-wave coupling) and the wave reflection (subtractive wave-wave coupling). The visualized growth rate is helpful in evaluating the maximum propagation angle to which the decay instability (of the parallel propagating pump Alfven wave) operates.</tt></p>

scholarly journals Wavevector spectral signature of decay instability in space plasmas

2020 ◽  
Author(s):  
Horia Comisel ◽  
Yasuhito Narita ◽  
Uwe Motschmann
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Space Plasma ◽  
Alfven Waves ◽  
Alfven Wave ◽  
Alfvén Waves ◽  
Wave Coupling ◽  
Decay Instability ◽  
Wavenumber Domain ◽  
Field Fluctuations

Abstract. Identification of a large-amplitude Alfven wave decaying into a pair of ion-acoustic and daughter Alfven waves is one of the major goals in the observational studies of space plasma nonlinearity. In this study, the decay instability is analytically evaluated in the 2-D wavenumber domain spanning the parallel and perpendicular directions to the mean magnetic field. The growth-rate determination of the density perturbations is based on the Hall-MHD wave-wave coupling theory for circularly-polarized Alfven waves. The diagrams of the growth rates versus the wavenumber and propagation angle derived in analytical studies are replaced by 2-D wavenumber distributions and compared with the corresponding wavevector spectrum of density and magnetic field fluctuations. The actual study reveals a perpendicular-shape spectral pattern consistent with the result of a previous study based on 3-D hybrid numerical simulations. The wavevector signature of the decay instability observed in the two-dimensional wavenumber domain ceases at values of plasma beta larger than beta = 0.1. Growth-rate maps serve as a useful tool for predictions of the wavevector spectrum of density or magnetic field fluctuations in various scenarios for the wave-wave coupling processes developing at different stages in space plasma turbulence.

scholarly journals Wavevector spectral signature of decay instability in space plasmas

2021 ◽  
Vol 39 (1) ◽  
pp. 165-170
Author(s):  
Horia Comişel ◽  
Yasuhito Narita ◽  
Uwe Motschmann
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Space Plasma ◽  
Alfven Waves ◽  
Alfven Wave ◽  
Alfvén Waves ◽  
Wave Coupling ◽  
Decay Instability ◽  
Wavenumber Domain ◽  
Field Fluctuations

Abstract. Identification of a large-amplitude Alfvén wave decaying into a pair of ion-acoustic and daughter Alfvén waves is one of the major goals in the observational studies of space plasma nonlinearity. In this study, the decay instability is analytically evaluated in the 2-D wavenumber domain spanning the parallel and perpendicular directions to the mean magnetic field. The growth-rate determination of the density perturbations is based on the Hall MHD (magnetohydrodynamic) wave–wave coupling theory for circularly polarized Alfvén waves. The diagrams of the growth rates versus the wavenumber and propagation angle derived in analytical studies are replaced by 2-D wavenumber distributions and compared with the corresponding wavevector spectrum of density and magnetic field fluctuations. The actual study reveals a perpendicular spectral pattern consistent with the result of a previous study based on 3-D hybrid numerical simulations. The wavevector signature of the decay instability observed in the two-dimensional wavenumber domain ceases at values of plasma beta larger than β=0.1. Growth-rate maps serve as a useful tool for predictions of the wavevector spectrum of density or magnetic field fluctuations in various scenarios for the wave–wave coupling processes developing at different stages in space plasma turbulence.

Parametric instabilities of circularly polarized large-amplitude dispersive Alfvén waves: excitation of parallel-propagating electromagnetic daughter waves

1991 ◽  
Vol 46 (1) ◽  
pp. 107-127 ◽  
Author(s):  
Adolfo F. Viñas ◽  
Melvyn L. Goldstein
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Large Amplitude ◽  
Wave Amplitude ◽  
Pump Wave ◽  
Modulational Instability ◽  
Alfven Wave ◽  
Circularly Polarized ◽  
Background Magnetic Field ◽  
Electromagnetic Instability

We investigate the parametric decay and modulational instabilities of a large-amplitude circularly polarized dispersive Alfvén wave. Our treatment is more general than that of previous derivations based on the two-fluid equations in that we allow for propagation of the unstable daughter waves at arbitrary angles to the background magnetic field, although our main concern in this paper is the exploration of new aspects of propagation parallel to the DC magnetic field. In addition to the well-known coupling of pump waves to electrostatic daughter waves, we find a new parametric channel where the pump wave couples directly to electromagnetic daughter waves. Excitation of the electromagnetic instability occurs only for modulation (k/k0 ≤ 1) and not for decay (k/k0 < 1). In contrast with the modulational instability excited by the electrostatic coupling, the electromagnetic modulational instability exists for both left-hand (K > 0) and right-hand (K < 0) polarization. For large k/k0, the electromagnetic channel dominates, while at lower values the electrostatic channel has a larger growth rate for modest values of dispersion, pump-wave amplitude and plasma β. Unlike the electrostatic modulational instability, the growth rate of the electromagnetic instability increases monotonically with increasing pump wave amplitude. This analysis confirms that, for decay, the dominant process is coupling to electrostatic daughter waves, at least for parallel propagation. For modulation, the coupling to electromagnetic daughter waves usually dominates, suggesting that the parametric modulational instability is really an electromagnetic phenomenon.

scholarly journals Alfven wave interactions within the Hall-MHD description

2013 ◽  
Vol 79 (5) ◽  
pp. 909-911 ◽  
Author(s):  
G. BRODIN ◽  
L. STENFLO
Keyword(s):  
Alfven Wave ◽  
Coupling Coefficients ◽  
Wave Interactions ◽  
Wave Coupling ◽  
Mhd Model ◽  
Model Equations ◽  
Hall Mhd

AbstractWe show that comparatively simple expressions for the Alfven wave coupling coefficients can be deduced from the well-known Hall-magnetohydrodynamics (MHD) model equations.

scholarly journals Thin current sheets and the associated wave activity observed by Solar Orbiter

2021 ◽  
Author(s):  
Daniel Graham ◽  
Yuri Khotyaintsev ◽  
Konrad Steinvall ◽  
Andris Vaivads ◽  
Milan Maksimovic ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Plasma Waves ◽  
Wave Activity ◽  
Number Density ◽  
Current Sheets ◽  
Field Fluctuations ◽  
Density Perturbations ◽  
The Waves ◽  
The Magnetic Field

&lt;p&gt;Thin current sheets are routinely observed in the solar wind. Here we report observations of thin current sheets and the associated plasma waves using the Solar Orbiter spacecraft. The Radio and Plasma Waves (RPW) instrument provides high-resolution measurements of the electric field, number density perturbations, and magnetic field fluctuations, which we use to identify and characterise the observed waves, while the magnetic field provided by the MAG instrument is used to characterise the current sheets. We discuss the role of current sheets in the generation of the observed waves and the effects of the waves on the current sheets.&lt;span&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt;

TOWARDS THE QUESTION OF SPECIALIZED FEEDS FOR TENCHES (TINCA TINCA)

2017 ◽  
pp. 89-97
Author(s):  
Elena Mikhaylovna Chervonenko ◽  
Lina Yurievna Lagutkina
Keyword(s):  
Growth Rate ◽  
Fish Growth ◽  
Animal Origin ◽  
State Technical ◽  
Tinca Tinca ◽  
Daily Growth ◽  
Volga River ◽  
The Moment ◽  
First Time ◽  
Technical Centre

The article describes the process of tench growing (male and female species removed from set gear in the Volga river in the Astrakhan region) using experimental feedstuff "T", taking into account the fact that problems with artificial growing tench ( Тinca tinca ) appear first in the process of feeding when wild sires change to artificial food. The research took place on the base of the department of aquaculture and water bioresources of Astrakhan State Technical University in innovation centre "Bioaquapark - scientific and technical centre of aquaculture" in 2015. Special feed including components of animal origin - mosquito grab and sludge worm as an effective substitute to fish flour, as well as components of vegetable origin (carrot, parsley, pumpkin, wheatgrass) for domestication of tenches are offered for the first time. Food technology has been described. The exact composition of the formula, which is being licensed at the moment, is not disclosed. Feed "T", which has undergone biological analysis and is in accordance with organoleptic and physical standards was used for feeding tench female and male species during domestication period (60 days), along with food "Coppens" (Holland). Feed efficiency was determined according to survival and daily fish growth. Growth rate of females appeared more intensive than growth rate of males fed with experimental food "T". Daily growth changed depending on the types of food: from 0.3 ("Coppens") to 0.47 (experimental food) in females, from 0.25 ("Coppens") to 0.39 (experimental food) with males. Ability to survive among tench species fed with "Coppens" and experimental food made 60% and 100%, correspondingly. Nutricion of tench species with experimental food encouraged their domestication, which allowed using tench species in further fish breeding process in order to get offspring. The project was supported by the Innovation Promotion Fund in terms of the project "Development and implementation of the technique for the steady development of aquaculture: food "TechSA".

scholarly journals The on-axis magnetic well and Mercier's criterion for arbitrary stellarator geometries

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
P. Kim ◽  
R. Jorge ◽  
W. Dorland
Keyword(s):  
Magnetic Field ◽  
Original Work ◽  
Three Dimensional ◽  
Radial Distance ◽  
Analytical Form ◽  
One Dimensional ◽  
Modern Notation ◽  
Magnetic Well ◽  
First Time ◽  
Dimensional Integral

A simplified analytical form of the on-axis magnetic well and Mercier's criterion for interchange instabilities for arbitrary three-dimensional magnetic field geometries is derived. For this purpose, a near-axis expansion based on a direct coordinate approach is used by expressing the toroidal magnetic flux in terms of powers of the radial distance to the magnetic axis. For the first time, the magnetic well and Mercier's criterion are then written as a one-dimensional integral with respect to the axis arclength. When compared with the original work of Mercier, the derivation here is presented using modern notation and in a more streamlined manner that highlights essential steps. Finally, these expressions are verified numerically using several quasisymmetric and non-quasisymmetric stellarator configurations including Wendelstein 7-X.

scholarly journals Evolutionary economics: Crisis, transformation and metamorphosis

2021 ◽  
pp. 1-8
Author(s):  
Milan Zeleny
Keyword(s):  
Growth Rate ◽  
Productivity Growth ◽  
Driving Force ◽  
Evolutionary Economics ◽  
Regional Economies ◽  
Economic Evolution ◽  
Economic Sectors ◽  
Advanced Economies ◽  
First Time

Most world economies are undergoing fundamental transformations of economic sectors, shifting their employed workforce through the secular sequence of (1. Agriculture⟶2. Industry⟶3. Services⟶4. Government). The productivity growth rate is the driving force. Most advanced economies have reached the final stages of the sequence. Assorted recessions, crises and stagnations are simply cofluent, accompanying phenomena. Crises might be cyclical, but economic evolution is unidirectional. Traditional economics can hardly distinguish phenomena of crisis from those of the transformation. Because there is no “fifth sector”, some economies are entering the phase of metamorphosis, for the first time in history. Metamorphosis is manifested through deglobalization, relocalization and autonomization of local and regional economies. We are entering the Age of Entrepreneurship.

Parametric excitation of magnetoacoustic waves by a pump magnetic field in a high-β plasma

1977 ◽  
Vol 17 (1) ◽  
pp. 93-103 ◽  
Author(s):  
N. F. Cramer
Keyword(s):  
Magnetic Field ◽  
Parametric Excitation ◽  
Acoustic Waves ◽  
Magnetic Pressure ◽  
Gas Pressure ◽  
Alfven Wave ◽  
Fast Wave ◽  
Magnetoacoustic Waves ◽  
Background Magnetic Field ◽  
The Waves

The parametric excitation of slow, intermediate (Alfvén) and fast magneto-acoustic waves by a modulated spatially non-uniform magnetic field in a plasma with a finite ratio of gas pressure to magnetic pressure is considered. The waves are excited in pairs, either pairs of the same mode, or a pair of different modes. The growth rates of the instabilities are calculated and compared with the known result for the Alfvén wave in a zero gas pressure plasma. The only waves that are found not to be excited are the slow plus fast wave pair, and the intermediate plus slow or fast wave pair (unless the waves have a component of propagation direction perpendicular to both the background magnetic field and the direction of non-uniformity of the field).

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