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Sample records for alfven wave heating

  1. Alfven wave heating

    International Nuclear Information System (INIS)

    The physics of Alfven-wave heating is particularly sensitive to the character of the linear mode conversion which occurs at the Alfven resonance layer. Parameter changes can profoundly affect both the location within the plasma and the mechanism for the power absorption. Under optimal conditions the heating power may be absorbed by electron Landau damping and by electron transit-time magnetic pumping in the plasma interior, or by the same processes acting near the resonance layer on the mode-converted kinetic Alfven wave. The method is outlined for computing the coefficients for reflection, transmission and absorption at the resonance layer and some representative results are offered

  2. Alfven wave heating and stability

    International Nuclear Information System (INIS)

    Alfven waves in fusion plasmas play an important role in a number of situations. First, in Alfven Wave Heating (AWH) schemes. Second, both theory and experiment have demonstrated the existence of Global Alfven Eigenmodes (GAEs). GAEs have been observed in different tokamaks (PRETEXT, TCA, TEXTOR, etc.) and, more recently, in a stellarator (Wendelstein 7-AS) where they were shown to become unstable under intense Neutral Beam injection. Third, the existence and possible destabilization by fast ions of Toroidicity induced Alfven Eigenmodes (TAEs) has been evidenced both theoretically and experimentally. This destabilization could hamper the operation of a magnetically confined fusion reactor by setting a limit on the number of fusion alpha particles in the plasma. It is therefore crucial to understand the mechanisms leading to the occurrence of the instability and also those that can stabilize the TAEs by increasing the strength of the damping. The aim is to be able to devise possible ways to avoid the instability of Alfven eigenmodes in a region of parameter space that is compatible with the functioning of a fusion reactor. A global perturbative approach is presented to tackle the problem of the linear stability of TAEs. Our model computes the overall wave particle power transfers to the different species and thus could also be applied to the study of alpha power extraction in the presence of Alfven waves. We indicate also how to go beyond the perturbative approach. (author) 15 figs., 38 refs

  3. Spheromak heating with Alfven waves

    International Nuclear Information System (INIS)

    The temperature of present spheromak plasmas will need to be raised in order to test the feasibility of the confinement concept. In addition, a spatially-selective rf heating pulse can be used to study transport. As the ohmic heating power within a spheromak can be quite large (6-MW), low frequencies where large amounts of power are available are preferred. For the Los Alamos spheromak experiment CTX, we propose to add heating energy via a shear Alfven wave resonance. This resonance can be made to occur upon a particular flux surface, thus depositing most of the energy locally. A 2-dimensional equilibrium code (toroidally symmetric) is used to establish flux surfaces and magnetic field values for the desired configuration, either with or without plasma pressure

  4. Alfven wave heating of a theta pinch

    International Nuclear Information System (INIS)

    The process of shear Alfven wave resonant absorption for plasma heating has been applied to a theta pinch. The m=1 mode is excited by means of a helical launching structure with a given wavelength, at a number of different frequencies. When the frequency lies in the continuous Alfven spectrum the kink energy is transferred to the Alfven wave and then is rapidly thermalized. The heating power is measured by a diamagnetic probe. It is shown that the probe signal can be treated as a thermodynamic variable permitting an exact energy balance to be deduced. The measured resonance curve of the heating power is in agreement with the predicted behaviour. A 50% efficiency is achieved and the coupling between the plasma and the external circuit is strong, in spite of the high compression ratio. (author)

  5. Plasma heating by kinetic Alfven wave

    International Nuclear Information System (INIS)

    The heating of a nonuniform plasma (electron-ion) due to the resonant excitation of the shear Alfven wave in the low β regime is studied using initially the ideal MHD model and posteriorly using the kinetic model. The Vlasov equation for ions and the drift kinetic equation for electrons have been used. Through the ideal MHD model, it is concluded that the energy absorption is due to the continuous spectrum (phase mixing) which the shear Alfven wave has in a nonuniform plasma. An explicit expression for the energy absorption is derived. Through the kinetic model it is concluded that the energy absorption is due to a resonant mode convertion of the incident wave into the kinetic Alfven wave which propagates away from the resonant region. Its electron Landau damping has been observed. There has been a concordance with the MHD calculations. (Author)

  6. Alfven wave

    International Nuclear Information System (INIS)

    Seven chapters are included. Chapters 1 and 2 introduce the Alfven wave and describe its linear properties in a homogeneous medium. Chapters 3 and 4 cover the effects of inhomogeneities on these linear properties. Particular emphasis is placed on the appearance of a continuum spectrum and the associated absorption of the Alfven wave which arise due to the inhomogeneity. The explanation of the physical origin of absorption is given using kinetic theory. Chapter 5 is devoted to the associated plasma instabilities. Nonlinear effects discussed in Chapter 6 include quasilinear diffusion, decay, a solitary wave, and a modulational instability. The principles of Alfven wave heating, a design example and present-day experimental results are described in Chapter 7

  7. The Source of Alfven Waves That Heat the Solar Corona

    Science.gov (United States)

    Ruzmaikin, A.; Berger, M. A.

    1998-01-01

    We suggest a source for high-frequency Alfven waves invoked in coronal heating and acceleration of the solar wind. The source is associated with small-scale magnetic loops in the chromospheric network.

  8. Alfven wave heating of current-carrying plasmas

    International Nuclear Information System (INIS)

    Alfven wave heating involves the excitation, by antenna currents, of MHD waves which mode convert to short wavelength quasi-electrostatic waves (QEW) at the Alfven resonance position. Over the past few years the authors developed the computer code ANTENNA which solves the kinetic theory equations that describe this process for a cylindrical model of a tokamak. Recently, the following improvements have been made to the code: Antennas with radial current elements can now be treated; arbitrary density and temperature profiles can be analysed; the kinetic theory wave equations have been formulated for arbitrary force-free plasma-current distributions

  9. A new way to convert Alfven waves into heat in solar coronal holes - Intermittent magnetic levitation

    Science.gov (United States)

    Moore, R. L.; Hammer, R.; Musielak, Z. E.; Suess, S. T.; An, C.-H.

    1992-01-01

    In our recent analysis of Alfven wave reflection in solar coronal holes, we found evidence that coronal holes are heated by reflected Alfven waves. This result suggests that the reflection is inherent to the process that dissipates these Alfven waves into heat. We propose a novel dissipation process that is driven by the reflection, and that plausibly dominates the heating in coronal holes.

  10. Density Limit in TCABR Plasmas With Alfven Wave Heating

    International Nuclear Information System (INIS)

    Alfven Waves (AW) were launched in tokamak (TCABR) density limit plasmas for the first time. Experimental evidence of plasma heating is backed up by calculations from an 1-D numerical cylindrical code, based on the toroidal electric field diffusion. Simultaneously, increase in the density limit and plasma pressure with negligible impurities level launched by the AW antennas were also observed, without major appearance of a resistive disruption. The increase in the density limit and the heating might be related to the expected edge and off-axis AW power deposition, respectively, in agreement with the calculation performed by an 1-D numerical code linked to ASTRA

  11. Ionospheric Ion Upflows Associated with the Alfven Wave Heating

    Science.gov (United States)

    Song, P.; Tu, J.

    2014-12-01

    In this study we present the simulation results from a self-consistent inductive-dynamic ionosphere-thermosphere model. In a 2-D numerical simulation (noon-midnight meridian plane), we solve the continuity, momentum, and energy equations for multiple species of ions and neutrals and Maxwell's equations. In particular, the model retains Faraday's law, inertial term in the ion momentum equations and photochemistry. The code is based on an implicit algorithm and simulates a region from 80 km to 5000 km above the Earth. The system is driven by an antisunward motion at the upper boundary of the dayside cusp latitude in both hemispheres. We show that the frictional heating, which can produce upflows of the light (H+ and He+) and heave (O+) ions, is driven by the Alfven wave-induced ion motion relative to the neutrals. The variations of the upflows along a noon-midnight magnetic meridian are examined in association with given driving conditions imposed by the magnetosphere convection.

  12. Solar off-limb line widths: Alfven waves, ion-cyclotron waves, and preferential heating

    CERN Document Server

    Dolla, L

    2008-01-01

    Alfven waves and ion-cyclotron absorption of high-frequency waves are frequently brought into models devoted to coronal heating and fast solar-wind acceleration. Signatures of ion-cyclotron resonance have already been observed in situ in the solar wind (HELIOS spacecrafts) and, recently, in the upper corona (UVCS/SOHO remote-sensing results). We propose a method to constrain both the Alfven wave amplitude and the preferential heating induced by ion-cyclotron resonance, above a partially developed polar coronal hole observed with the SUMER/SOHO spectrometer. The instrumental stray light contribution is first substracted from the spectra. By supposing that the non-thermal velocity is related to the Alfven wave amplitude, it is constrained through a density diagnostic and the gradient of the width of the Mg X 625 A line. The temperatures of several coronal ions, as functions of the distance above the limb, are then determined by substracting the non-thermal component to the observed line widths. The effect of st...

  13. Theory of heating of hot magnetized plasma by Alfven waves. Application for solar corona

    OpenAIRE

    Mishonov, T. M.; Stoev, M. V.; Maneva, Y. G.

    2007-01-01

    The heating of magnetized plasma by propagation of Alfven waves is calculated as a function of the magnetic field spectral density. The results can be applied to evaluate the heating power of the solar corona at known data from satellites' magnetometers. This heating rate can be incorporated in global models for heating of the solar corona and creation of the solar wind. The final formula for the heating power is illustrated with a model spectral density of the magnetic field obtained by anal...

  14. Shear Alfven waves in tokamaks

    International Nuclear Information System (INIS)

    Shear Alfven waves in an axisymmetric tokamak are examined within the framework of the linearized ideal MHD equations. Properties of the shear Alfven continuous spectrum are studied both analytically and numerically. Implications of these results in regards to low frequency rf heating of toroidally confined plasmas are discussed. The structure of the spatial singularities associated with these waves is determined. A reduced set of ideal MHD equations is derived to describe these waves in a very low beta plasma

  15. Alfven wave spectrum control in the heating and current drive experiments

    International Nuclear Information System (INIS)

    In this report we present the diagnostic system that has been developed for wave field spectrum analysis and control during Alfven wave heating and current drive experiments in the TCABR tokamak The system permits to register simultaneously the phase and the amplitude of the toroidal Β-tilde φ and poloidal Β-tildeθ magnetic field components of the waves with M ±1, N = ±, N = ±(2+6) in the frequency range ∫ = 2-8 MHz and RF pulse duration τ = 20-50 ms and to generate a feedback signal for plasma parameters control. The wave mode and frequency selectivity are ensured by the adjustment of the magnetic probe position and by utilization of specially designed 'lock-in' amplifiers that use 'sin' and 'cos' reference signals produced on the basis of the Alfven antenna feeding current. (author)

  16. Kinetic effects in Alfven wave heating Part 2 propagation and absorption with a single minority species

    International Nuclear Information System (INIS)

    Kinetic effects of Alfven wave spatial resonances near the plasma edge are investigated numerically and analytically in a cylindrical tokamak model. In Part 1, cold plasma surface Alfven eigenmodes (SAE's) in a pure plasma are examined. Numerical calculations of antenna-driven waves exhibiting absorption resonances at certain discrete frequencies are first reviewed. From a simplified kinetic equation, an analytical dispersion relation is then obtained with the antenna current set equal to zero. The real and imaginary parts of its roots, which are the complex eigenfrequencies, agree with the central frequencies and widths, respectively, of the numerical antenna-driven resonances. These results serve as an introduction to the companion paper, in which it is shown that, in the presence of a minority species, certain SAE's, instead of heating the plasma exterior, can dissipate substantial energy in the two-ion hybrid layer near the plasma center. 11 refs., 8 figs., 1 tab

  17. The role of Alfv\\'en wave heating in solar prominences

    CERN Document Server

    Soler, Roberto; Oliver, Ramon; Ballester, Jose Luis

    2016-01-01

    Observations have shown that magnetohydrodynamic waves over a large frequency range are ubiquitous in solar prominences. The waves are probably driven by photospheric motions and may transport energy up to prominences suspended in the corona. Dissipation of wave energy can lead to heating of the cool prominence plasma, so contributing to the local energy balance within the prominence. Here we discuss the role of Alfv\\'en wave dissipation as a heating mechanism for the prominence plasma. We consider a slab-like quiescent prominence model with a transverse magnetic field embedded in the solar corona. The prominence medium is modelled as a partially ionized plasma composed of a charged ion-electron single fluid and two separate neutral fluids corresponding to neutral hydrogen and neutral helium. Friction between the three fluids acts as a dissipative mechanism for the waves. The heating caused by externally-driven Alfv\\'en waves incident on the prominence slab is analytically explored. We find that the dense pro...

  18. The Spatial and Temporal Dependence of Coronal Heating by Alfven Wave Turbulence

    CERN Document Server

    Asgari-Targhi, M; Cranmer, S R; DeLuca, E E

    2013-01-01

    The solar atmosphere may be heated by Alfven waves that propagate up from the convection zone and dissipate their energy in the chromosphere and corona. To further test this theory, we consider wave heating in an active region observed on 2012 March 7. A potential field model of the region is constructed, and 22 field lines representing observed coronal loops are traced through the model. Using a three-dimensional (3D) reduced magneto-hydrodynamics (MHD) code, we simulate the dynamics of Alfven waves in and near the observed loops. The results for different loops are combined into a single formula describing the average heating rate Q as function of position within the observed active region. We suggest this expression may be approximately valid also for other active regions, and therefore may be used to construct 3D, time-dependent models of the coronal plasma. Such models are needed to understand the role of thermal non-equilibrium in the structuring and dynamics of the Sun's corona.

  19. Advanced antenna system for Alfven wave plasma heating and current drive in TCABR tokamak

    International Nuclear Information System (INIS)

    An advanced antenna system that has been developed for investigation of Alfven wave plasma heating and current drive in the TCABR tokamak is described. The main goal was the development of such a system that could insure the excitation of travelling single helicity modes with predefined wave mode numbers M and N. The system consists of four similar modules with poloidal windings. The required spatial spectrum is formed by proper phasing of the RF feeding currents. The impedance matching of the antenna with the four-phase oscillator is accomplished by resonant circuits which form one assembly unit with the RF feeders. The characteristics of the antenna system design with respect to the antenna-plasma coupling and plasma wave excitation, for different phasing of the feeding currents, are summarised. The antenna complex impedance Z=ZR+ZI is calculated taking into account both the plasma response to resonant excitation of fast Alfven waves and the nonresonant excitation of vacuum magnetic fields in conducting shell. The matching of the RF generator with the antenna system during plasma heating is simulated numerically, modelling the plasma response with mutually coupled effective inductances with corresponding active ZR and reactive ZI impedances. The results of the numerical simulation of the RF system performance, including both the RF magnetic field spectrum analysis and the modeling of the RF generator operation with plasma load, are presented. (orig.)

  20. Design of the RF system for Alfven wave heating and current drive in a TCA/BR tokamak

    International Nuclear Information System (INIS)

    The advanced RF system for Alfven wave plasma heating and current drive in TCA/BR tokamak is presented. The antenna system is capable of exciting the standing and travelling wave M = -1,N = 1,N =-4,-6 with single helicity and thus provides the possibility to improve Alfven wave plasma heating efficiency in TCA/BR tokamak and to increase input power level up to P ≅ 1 MW, without the uncontrolled density rise which was encountered in previous TCA (Switzerland) experiments. (author). 4 refs., 3 figs

  1. An experimental study of the harmonics generated during Alfven wave heating in TCA

    International Nuclear Information System (INIS)

    During plasma excitation by high power Alfven waves in TCA, signals at harmonics of the generator frequency are observed in the plasma scrape-off layer. In this paper we report experimental investigations of the sheath effect and the excitation efficiency and dispersion properties of these harmonics. The results indicate that the harmonics arise either directly or indirectly through the driven Alfven waves and not the sheath effect at the exciting antenna. The RF ion saturation current is observed a non-negligible peak amplitude in comparison to the time averaged ion saturation current and may provide evidence of non-linear evolution of the driven Alfven waves. (author) 8 figs., 8 refs

  2. PERPENDICULAR ION HEATING BY LOW-FREQUENCY ALFVEN-WAVE TURBULENCE IN THE SOLAR WIND

    International Nuclear Information System (INIS)

    We consider ion heating by turbulent Alfven waves (AWs) and kinetic Alfven waves (KAWs) with wavelengths (measured perpendicular to the magnetic field) that are comparable to the ion gyroradius and frequencies ω smaller than the ion cyclotron frequency Ω. We focus on plasmas in which β ∼ρ/vperpendicular, where vperpendicular (v ||) is the component of the ion velocity perpendicular (parallel) to the background magnetic field B 0, and δv ρ (δB ρ) is the rms amplitude of the velocity (magnetic-field) fluctuations at the gyroradius scale. In the case of thermal protons, when ε crit, where εcrit is a constant, a proton's magnetic moment is nearly conserved and stochastic heating is extremely weak. However, when ε>εcrit, the proton heating rate exceeds half the cascade power that would be present in strong balanced KAW turbulence with the same value of δv ρ, and magnetic-moment conservation is violated even when ω crit = 0.19. For protons in low-β plasmas, ε ≅ β-1/2δBρ/B 0, and ε can exceed εcrit even when δBρ/B 0 crit. The heating is anisotropic, increasing v 2perpendicular much more than v 2|| when β 1 Landau damping and transit-time damping of KAWs lead to strong parallel heating of protons.) At comparable temperatures, alpha particles and minor ions have larger values of ε than protons and are heated more efficiently as a result. We discuss the implications of our results for ion heating in coronal holes and the solar wind.

  3. Hybrid Model of Inhomogeneous Solar Wind Plasma Heating by Alfven Wave Spectrum: Parametric Studies

    Science.gov (United States)

    Ofman, L.

    2010-01-01

    Observations of the solar wind plasma at 0.3 AU and beyond show that a turbulent spectrum of magnetic fluctuations is present. Remote sensing observations of the corona indicate that heavy ions are hotter than protons and their temperature is anisotropic (T(sub perpindicular / T(sub parallel) >> 1). We study the heating and the acceleration of multi-ion plasma in the solar wind by a turbulent spectrum of Alfvenic fluctuations using a 2-D hybrid numerical model. In the hybrid model the protons and heavy ions are treated kinetically as particles, while the electrons are included as neutralizing background fluid. This is the first two-dimensional hybrid parametric study of the solar wind plasma that includes an input turbulent wave spectrum guided by observation with inhomogeneous background density. We also investigate the effects of He++ ion beams in the inhomogeneous background plasma density on the heating of the solar wind plasma. The 2-D hybrid model treats parallel and oblique waves, together with cross-field inhomogeneity, self-consistently. We investigate the parametric dependence of the perpendicular heating, and the temperature anisotropy in the H+-He++ solar wind plasma. It was found that the scaling of the magnetic fluctuations power spectrum steepens in the higher-density regions, and the heating is channeled to these regions from the surrounding lower-density plasma due to wave refraction. The model parameters are applicable to the expected solar wind conditions at about 10 solar radii.

  4. CHROMOSPHERIC EVAPORATION VIA ALFVEN WAVES

    International Nuclear Information System (INIS)

    This paper presents a scenario for the chromospheric evaporation during solar flares, which is inspired by the chain of events leading to the formation of auroral arcs and ionospheric evacuation during magnetospheric substorms. The plasma, ejected from high coronal altitudes during a flare reconnection event, accumulates at the tops of coronal loops by braking of the reconnection flow, possibly by fast shock formation. A high-beta layer forms and distorts the magnetic field. Energy contained in magnetic shear stresses is transported as Alfven waves from the loop-top toward the chromosphere. It is shown that under these conditions the Alfven waves carry enough energy to feed the chromospheric evaporation process. The second subject of this investigation is identification of the most effective energy dumping or wave dissipation process. Several processes are being analyzed: ion-neutral collisions, classical and anomalous field-aligned current dissipation, and critical velocity ionization. All of them are being discarded, either because they turn out to be insufficient or imply very unlikely physical properties of the wave modes. It is finally concluded that turbulent fragmentation of the Alfven waves entering the chromosphere can generate the required damping. The basic process would be phase mixing caused by a strongly inhomogeneous distribution of Alfvenic phase speed and laminar flow breakup by Kelvin-Helmholtz (K-H) instability. The filamentary (fibril) structure of the chromosphere thus appears to be essential for the energy conversion, in which the K-H instability is the first step in a chain of processes leading to ion thermalization, electron heating, and neutral particle ionization. Quantitative estimates suggest that a transverse structure with scales not far below 100 km suffices to produce strong wave damping within a few seconds. Nonthermal broadening of some metallic ion lines observed during the pre-impulsive rise phase of a flare might be a residue of

  5. Alfven wave. DOE Critical Review Series

    International Nuclear Information System (INIS)

    This monograph deals with the properties of Alfven waves and with their application to fusion. The book is divided into 7 chapters dealing with linear properties in homogeneous and inhomogeneous plasmas. Absorption is treated by means of kinetic theory. Instabilities and nonlinear processes are treated in Chapters 1 to 6, and the closing chapter is devoted to theory and experiments in plasma heating by Alfven waves

  6. Alfven wave. DOE Critical Review Series

    Energy Technology Data Exchange (ETDEWEB)

    Hasegawa, A.; Uberoi, C.

    1982-01-01

    This monograph deals with the properties of Alfven waves and with their application to fusion. The book is divided into 7 chapters dealing with linear properties in homogeneous and inhomogeneous plasmas. Absorption is treated by means of kinetic theory. Instabilities and nonlinear processes are treated in Chapters 1 to 6, and the closing chapter is devoted to theory and experiments in plasma heating by Alfven waves. (MOW)

  7. On the coronal heating mechanism by the resonant absorption of Alfven waves

    Directory of Open Access Journals (Sweden)

    H. Y. Alkahby

    1993-12-01

    Full Text Available In this paper, we will investigate the heating of the solar corona by the resonant absorption of Alfven waves in a viscous and isothermal atmosphere permeated by a horizontal magnetic field. It is shown that if the viscosity dominates the motion in a high (low- β plasma, it creates an absorbing and reflecting layer and the heating process is acoustic (magnetoacoustic. When the magnetic field dominates the oscillatory process it creates a non-absorbing reflecting layer. Consequently, the heating process is magnetohydrodynamic. An equation for resonance is derived. It shows that resonances may occur for many values of the frequency and of the magnetic field if the wavelength is matched with the strength of the magnetic field. At the resonance frequencies, magnetic and kinetic energies will increase to very large values which may account for the heating process. When the motion is dominated by the combined effects of the viscosity and the magnetic field, the nature of the reflecting layer and the magnitude of the reflection coefficient depend on the relative strengths of the magnetic field and the viscosity.

  8. The Modulation of Ionospheric Alfven Resonator on Heating HF Waves and the Doppler Effect

    Institute of Scientific and Technical Information of China (English)

    NiBin-bin; ZhaoZheng-yu; XieShu-guo

    2003-01-01

    The propagation of HF waves in IAR can produce many nonlinear effects, including the modulation effect of IAR on HF waves and the Doppler effect. To start with the dependence of the ionospheric electron temperature varia-tions on the Alfven resonant field, We discuss the mechanism of the modulation effect and lucubrate possible reasons for the Doppler effect. The results show that the Alfven resonant field can have an observable modulation effect on HF waves while its mechanism is quite different from that of Schumann resonant field on HF waves. The depth of modulation of IAR on HF waves has a quasi-quadratic relation with the Alfven field, which directly inspires the formation of cross-spectrum between ULF waves and HF waves and results in spectral peaks at some gyro-frequencies of IAR. With respect to the Doppler effect during the propagation of HF waves in IAR, it is mainly caused by the motion of the high-speed flyer and the drifting electrons and the frequency shift from the phase vari-ation of the reflected waves can be neglected when the frequency of HF incident wave is high enough.

  9. Heating and Acceleration of the Fast Solar Wind by Alfv\\'{e}n Wave Turbulence

    CERN Document Server

    van Ballegooijen, A A

    2016-01-01

    We present numerical simulations of reduced magnetohydrodynamic (RMHD) turbulence in a magnetic flux tube at the center of a polar coronal hole. The model for the background atmosphere is a solution of the momentum equation, and includes the effects of wave pressure on the solar wind outflow. Alfv\\'{e}n waves are launched at the coronal base, and reflect at various heights due to variations in Alfv\\'{e}n speed and outflow velocity. The turbulence is driven by nonlinear interactions between the counter-propagating Alfv\\'{e}n waves. Results are presented for two models of the background atmosphere. In the first model the plasma density and Alfv\\'{e}n speed vary smoothly with height, resulting in minimal wave reflections and low energy dissipation rates. We find that the dissipation rate is insufficient to maintain the temperature of the background atmosphere. The standard phenomenological formula for the dissipation rate significantly overestimates the rate derived from our RMHD simulations, and a revised formu...

  10. Current generation by the Kinetic Alfven wave

    International Nuclear Information System (INIS)

    The current generated and the efficiency of the shear Kinetic Alfven wave are obtained using a self-consistent quasilinear formulation. Also, the current generation by the monochromatic shear Kinetic Alfven wave introduced by Hasegawa is re-examined taking into account the nonresonant electrons. To obtain the RF current density at the level of the ohmic heating current density in a tokamak, the required external magnetic field is smaller than 0.1% of the DC magnetic field, and the parallel electric field (E2), using the Lausanne-TCA-Tokamak parameters is of the order of 0.01 V cm-1. (author)

  11. The use of Alfven waves in NET

    International Nuclear Information System (INIS)

    A number of features of Alfven wave heating make it potentially attractive for use in large tokamac reactors. Among them are the availability and relatively low cost of the power supplies, the potential ability to act selectively on the current profile, and the probable absence of operational limits in size, fields or density. (author) 26 figs., 10 tabs., 54 refs

  12. The nonlinear compressional Alfven wave equation

    International Nuclear Information System (INIS)

    The nonlinear wave equation of the compressional Alfven mode is derived in Lagrangian fluid coordinate. The nonlinearity attributes unequal weight to the terms of temporal and spatial derivatives. Two specific solutions relevant to transit-time magnetic pumping plasma heating and theta-pinch implosions are given. (Author)

  13. Alfvenic Heating of Protostellar Accretion Disks

    OpenAIRE

    Vasconcelos, M. J.; Jatenco-Pereira, V.; R. Opher

    1999-01-01

    We investigate the effects of heating generated by damping of Alfven waves on protostellar accretion disks. Two mechanisms of damping are investigated, nonlinear and turbulent, which were previously studied in stellar winds (Jatenco-Pereira & Opher 1989a, b). For the nominal values studied, f=delta v/v_{A}=0.002 and F=varpi/Omega_{i}=0.1, where delta v, v_{A} and varpi are the amplitude, velocity and average frequency of the Alfven wave, respectively, and Omega_{i} is the ion cyclotron freque...

  14. Alfven waves: a journey between space and fusion plasmas

    International Nuclear Information System (INIS)

    Alfven waves discovered by Hannes Alfven (1942 Nature 150 405) are fundamental electromagnetic oscillations in magnetized plasmas existing in the nature and laboratories. Alfven waves play important roles in the heating, stability and transport of plasmas. The anisotropic nearly incompressible shear Alfven wave is particularly interesting since, in realistic non-uniform plasmas, its wave spectra consist of both the regular discrete and the singular continuous components. In this Alfven lecture, I will discuss these spectral properties and examine their significant linear and nonlinear physics implications. These discussions will be based on perspectives from my own research in both space and laboratory fusion plasmas, and will demonstrate the positive feedback and cross-fertilization between these two important sub-disciplines of plasma physics research. Some open issues of nonlinear Alfven wave physics in burning fusion as well as magnetospheric space plasmas will also be explored.

  15. Rogue waves in Alfvenic turbulence

    International Nuclear Information System (INIS)

    Rogue waves, in the form of giant breathers, are shown to develop in the Alfven wave (AW) turbulence regime described by the randomly driven derivative nonlinear Schroedinger equation in the presence of a weak dissipation. The distribution of the instantaneous global maxima of the AW intensity fluctuations is seen to be accurately fitted by power laws, which contrasts with the integrable regime (absence of dissipation and forcing) where the behavior is rather exponential. As the dissipation is reduced, freak waves form less frequently but reach larger amplitudes. -- Highlights: → Rogue wave formation in long-wavelength Alfvenic turbulence. → Huge waves form by quasi-collapse of breathers in presence of weak dissipation. → Amplitude distribution of rogue waves is fitted by power laws. → Possible relation with SLAMS pulses observed near the Earth bow shock.

  16. Spectrum of compressional Alfven waves

    International Nuclear Information System (INIS)

    The spectrum of compressional Alfven eigenmodes localized in the potential well created by a combination of the variation in plasma density and the wave number k/sub perpendicular to/ = m/r, is obtained, and its importance for ratio frequency current drive is discussed. It is found that modes with small parallel wave numbers and frequencies below the ion cyclotron frequency are attractive for current drive

  17. Development of Alfven wave antenna system for TCABR Tokamak

    International Nuclear Information System (INIS)

    The advanced antenna system for Alfven wave plasma heating and current drive in TCABR tokamak is presented. The antenna system is capable of exciting the travelling waves M=- 1, N=-4, -6 with single helicity and provides the possibility to improve Alfven wave plasma heating efficiency and to increase RF power input up 1 MW, without an uncontrolled density rise. The basic features of the antenna design and the results of preliminary tests are analyzed. (author)

  18. Toroidal Alfven wave stability in ignited tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, C.Z.; Fu, G.Y.; Van Dam, J.W.

    1989-01-01

    The effects of fusion-product alpha particles on the stability of global-type shear Alfven waves in an ignited tokamak plasma are investigated in toroidal geometry. Finite toroidicity can lead to stabilization of the global Alfven eigenmodes, but it induces a new global shear Alfven eigenmodes, which is strongly destabilized via transit resonance with alpha particles. 8 refs., 2 figs.

  19. Alfv\\'en Wave Turbulence as a Coronal Heating Mechanism: Simultaneously Predicting the Heating Rate and the Wave-Induced Emission Line Broadening

    CERN Document Server

    Oran, R; van der Holst, B; Sokolov, I V; Gombosi, T I

    2014-01-01

    In the present work, we test the predictions of the AWSoM model, a global extended-MHD model capable of calculating the propagation and turbulent dissipation of Alfv\\'en waves in any magnetic topology, against high resolution spectra of the quiescent off-disk solar corona. Wave dissipation is the only heating mechanism assumed in this model. Combining 3D model results with the CHIANTI atomic database, we were able to create synthetic line-of-sight spectra which include the effects of emission line broadening due to both thermal and wave-related non-thermal motions. To the best of our knowledge this is the first time a global model is used to obtain synthetic non-thermal line broadening. We obtained a steady-state solution driven by a synoptic magnetogram and compared the synthetic spectra with SUMER observations of a quiescent area above the solar west limb extending between 1.04 and 1.34 solar radii at the equator. Both the predicted line widths and the total line fluxes were consistent with the observations...

  20. Interchange Reconnection Alfven Wave Generation

    CERN Document Server

    Lynch, B J; Li, Y

    2014-01-01

    Given recent observational results of interchange reconnection processes in the solar corona and the theoretical development of the S-Web model for the slow solar wind, we present further analysis of the 3D MHD simulation of interchange reconnection by Edmondson et al. (Astrophys. J. 707, 1427, 2009). Specifically, we analyze the consequences of the dynamic streamer belt jump that corresponds to flux opening by interchange reconnection. Information about the magnetic field restructuring by interchange reconnection is carried throughout the system by Alfven waves propagating away from the reconnection region, distributing the shear and twist imparted by the driving flows, including shedding the injected stress-energy and accumulated magnetic helicity along newly-open field lines. We quantify the properties of the reconnection-generated wave activity in the simulation. There is a localized high frequency component associated with the current sheet/reconnection site and an extended low frequency component associ...

  1. A laboratory search for plasma erosion by Alfven waves

    Science.gov (United States)

    Vincena, S.; Gekelman, W.; Pribyl, P.

    2007-12-01

    Obliquely propagating shear Alfven waves with transverse wavelengths on the order of the electron inertial length or even the ion gyro-radius are commonly observed in the earth's low-altitude auroral zones. These regions are also replete with observations of electron beams and transversely heated ions. A kinetic treatment of shear Alfven wave-particle interaction reveals how these waves can be responsible for some of the observed particle acceleration. The auroral plasma environment is further enriched by the presence of field-aligned depletions in plasma density, and it has been suggested* that the Alfven waves may, in fact, be the cause of the erosion of ionospheric density. In this laboratory experiment, shear waves will be launched using a variety of proven antennas, and also allowed to grow spontaneously as Drift-Alfven modes in seeded density depletions**. Detailed measurements of the wave magnetic fields in the perpendicular density gradient regions will be presented which demonstrate the generation of short perpendicular wave scales due to the perpendicular gradient in parallel wave phase speed. Miniature in-situ particle diagnostics will also be used to look for electron and ion acceleration. The waves will also be launched into an increasing region of background magnetic field in an attempt to model the ratios of Alfven speed to electron thermal speed, and density gradient scale length to electron inertial length appropriate to the earth's auroral zone. Preliminary results will be presented on the efficacy of shear Alfven waves to self-generate plasma density depletions, or deepen ambient density inhomogeneities. The experiments are conducted at UCLA's Basic Plasma Science Facility in the Large Plasma Device. *Chaston, et al., "Ionospheric erosion by Alfven Waves," JGR, V 111, A03206, 2006. **Penano, et al., "Drift-Alfven fluctuations associated with a narrow pressure striation," Phys. Plasmas, V 7, Issue 1, pp. 144-157 (2000).

  2. Ion temperature in plasmas with intrinsic Alfven waves

    Science.gov (United States)

    Wu, C. S.; Yoon, P. H.; Wang, C. B.

    2014-10-01

    This Brief Communication clarifies the physics of non-resonant heating of protons by low-frequency Alfvenic turbulence. On the basis of general definition for wave energy density in plasmas, it is shown that the wave magnetic field energy is equivalent to the kinetic energy density of the ions, whose motion is induced by the wave magnetic field, thus providing a self-consistent description of the non-resonant heating by Alfvenic turbulence. Although the study is motivated by the research on the solar corona, the present discussion is only concerned with the plasma physics of the heating process.

  3. Simulations of Alfven wave driving of the solar chromosphere - efficient heating and spicule launching

    CERN Document Server

    Brady, C S

    2016-01-01

    Two of the central problems in our understanding of the solar chromosphere are how the upper chromosphere is heated and what drives spicules. Estmates of the required chromospheric heating, based on radiative and conductive losses suggest a rate of $\\sim 0.1 \\mathrm{\\:erg\\:cm^{-3}\\:s^{-1}}$ in the lower chromosphere dropping to $\\sim 10^{-3} \\mathrm{\\:erg\\:cm^{-3}\\:s^{-1}}$ in the upper chromosphere (\\citet{Avrett1981}). The chromosphere is also permeated by spicules, higher density plasma from the lower atmosphere propelled upwards at speeds of $\\sim 10-20 \\mathrm{\\:km\\:s^{-1}}$, for so called Type-I spicules (\\citet{Pereira2012,Zhang2012}, reaching heights of $\\sim 3000-5000 \\mathrm{\\:km}$ above the photosphere. A clearer understanding of chromospheric dynamics, its heating and the formation of spicules, is thus of central importance to solar atmospheric science. For over thirty years it has been proposed that photospheric driving of MHD waves may be responsible for both heating and spicule formation. This ...

  4. Simulations of the Mg II k and Ca II 8542 lines from an Alfv\\'en Wave-heated flare chromosphere

    CERN Document Server

    Kerr, Graham S; Russell, Alexander J B; Allred, Joel C

    2016-01-01

    We use radiation hydrodynamic simulations to examine two models of solar flare chromospheric heating: Alfv\\'en wave dissipation and electron beam collisional losses. Both mechanisms are capable of strong chromospheric heating, and we show that the distinctive atmospheric evolution in the mid-to-upper chromosphere results in Mg II k-line emission that should be observably different between wave-heated and beam-heated simulations. We also present Ca II 8542A profiles which are formed slightly deeper in the chromosphere. The Mg II k-line profiles from our wave-heated simulation are quite different from those from a beam-heated model and are more consistent with IRIS observations. The predicted differences between the Ca II 8542A in the two models are small. We conclude that careful observational and theoretical study of lines formed in the mid-to-upper chromosphere holds genuine promise for distinguishing between competing models for chromospheric heating in flares.

  5. Nonlinear standing Alfven wave current system at Io: Theory

    International Nuclear Information System (INIS)

    We present a nonlinear analytical model of the Alfven current tubes continuing the currents through Io (or rather its ionosphere) generated by the unipolar inductor effect due to Io's motion relative to the magnetospheric plasma. We thereby extend the linear work by Drell et al. (1965) to the fully nonlinear, sub-Alfvenic situation also including flow which is not perpendicular to the background magnetic field. The following principal results have been obtained: (1) The portion of the currents feeding Io is aligned with the Alfven characteristics at an angle theta/sub A/ is the Alfven Mach number. (2) The Alfven tubes act like an external conductance Σ/sub A/=1/(μ0V/sub A/(1+M/sub A/2+2M/sub A/ sin theta)/sup 1/2/ where V/sub A/ is the Alfven wave propagation. Hence the Jovian ionospheric conductivity is not necessary for current closure. (3) In addition, the Alfven tubes may be reflected from either the torus boundary or the Jovian ionosphere. The efficiency of the resulting interaction with these boundaries varies with Io position. The interaction is particularly strong at extreme magnetic latitudes, thereby suggesting a mechanism for the Io control of decametric emissions. (4) The reflected Alfven waves may heat both the torus plasma and the Jovian ionosphere as well as produce increased diffusion of high-energy particles in the torus. (5) From the point of view of the electrodynamic interaction, Io is unique among the Jovian satellites for several reasons: these include its ionosphere arising from ionized volcanic gases, a high external Alfvenic conductance Σ/sub A/, and a high corotational voltage in addition to the interaction phenomenon with a boundary. (6) We find that Amalthea is probably strongly coupled to Jupiter's ionosphere while the outer Galilean satellites may occasionally experience super-Alfvenic conditions

  6. Alfven Wave Tomography for Cold MHD Plasmas

    International Nuclear Information System (INIS)

    Alfven waves propagation in slightly nonuniform cold plasmas is studied by means of ideal magnetohydrodynamics (MHD) nonlinear equations. The evolution of the MHD spectrum is shown to be governed by a matrix linear differential equation with constant coefficients determined by the spectrum of quasi-static plasma density perturbations. The Alfven waves are shown not to affect the plasma density inhomogeneities, as they scatter off of them. The application of the MHD spectrum evolution equation to the inverse scattering problem allows tomographic measurements of the plasma density profile by scanning the plasma volume with Alfven radiation

  7. Alfvenic waves in solar spicules

    Science.gov (United States)

    Ebadi, Hossein

    2016-07-01

    We analyzed O VI (1031.93 A) and O VI (1037.61 A line profiles from the time series of SOHO/SUMER data. The wavelet analysis is used to determine the fundamental mode and its first harmonic periods and their ratio. The period ratio, P_1/P_2 is obtained as 2.1 based on our calculations. To model the spicule oscillations, we consider an equilibrium configuration in the form of an expanding straight magnetic flux tube with varying density along tube. We used cylindrical coordinates r, phi, and z with the z-axis along tube axis. Standing Alfvenic waves with steady flows are studied. More realistic background magnetic field, plasma density, and spicule radios inferred from the actual magnetoseismology of observations are used. It is found that the oscillation periods and their ratio are shifted because of the steady flows. The observational values are reached in P_1/P_2, when the steady flows are 0.2-0.3, the values which are reported for classical spicules.

  8. On Alfvenic Waves and Stochastic Ion Heating with 1Re Observations of Strong Field-aligned Currents, Electric Fields, and O+ ions

    Science.gov (United States)

    Coffey, Victoria; Chandler, Michael; Singh, Nagendra

    2008-01-01

    The role that the cleft/cusp has in ionosphere/magnetosphere coupling makes it a very dynamic region having similar fundamental processes to those within the auroral regions. With Polar passing through the cusp at 1 Re in the Spring of 1996, we observe a strong correlation between ion heating and broadband ELF (BBELF) emissions. This commonly observed relationship led to the study of the coupling of large field-aligned currents, burst electric fields, and the thermal O+ ions. We demonstrate the role of these measurements to Alfvenic waves and stochastic ion heating. Finally we will show the properties of the resulting density cavities.

  9. Alfven wave cascades in a tokamak

    International Nuclear Information System (INIS)

    Experiments designed for generating internal transport barriers in the plasmas of the Joint European Torus [JET, P. H. Rebut et al., Proceedings of the 10th International Conference, Plasma Physics and Controlled Nuclear Fusion, London (International Atomic Energy Agency, Vienna, 1985), Vol. I, p. 11] reveal cascades of Alfven perturbations with predominantly upward frequency sweeping. These experiments are characterized by a hollow plasma current profile, created by lower hybrid heating and current drive before the main heating power phase. The cascades are driven by ions accelerated with ion cyclotron resonance heating (ICRH). Each cascade consists of many modes with different toroidal mode numbers and different frequencies. The toroidal mode numbers vary from n=1 to n=6. The frequency starts from 20 to 90 kHz and increases up to the frequency range of toroidal Alfven eigenmodes. In the framework of ideal magnetohydrodynamics (MHD) model, a close correlation is found between the time evolution of the Alfven cascades and the evolution of the Alfven continuum frequency at the point of zero magnetic shear. This correlation facilitates the study of the time evolution of both the Alfven continuum and the safety factor, q(r), at the point of zero magnetic shear and makes it possible to use Alfven spectroscopy for studying q(r). Modeling shows that the Alfven cascade occurs when the Alfven continuum frequency has a maximum at the zero shear point. Interpretation of the Alfven cascades is given in terms of a novel-type of energetic particle mode localized at the point where q(r) has a minimum. This interpretation explains the key experimental observations: simultaneous generation of many modes, preferred direction of frequency sweeping, and the absence of strong continuum damping

  10. Alfven wave structure and resonant dissipation in cylindrical stability and heating problems

    International Nuclear Information System (INIS)

    For /ω/ approximately equal to epsilonsup(1/3)tausub(A)sup(-1), we obtain the general solution of the resistive differential equation for the radial M.H.D. displacement in cylindrical geometry, under the assumption of incompressibility. Here: ω is the wave frequency, Tausub(A) = r0 Vsub(Atheta)sup(-1), r = r0 is the surface at which q(r) = 1, Vsub(Atheta) = Btheta0/√4πrho[r0 dq0/dr] (subscript zero indicates evaluation at r0), epsilon = tausub(A) tausub(R)sup(-1) and tausub(R) is the resistive diffusion time. By using a flux function, we write the expression of the electromagnetic field and current density in the resistive layer. Finally, we discuss power dissipated in this layer by an external wave and the limit when the resistivity vanishes

  11. First Results of PIC Modeling of Kinetic Alfven Wave Dissipation

    Science.gov (United States)

    Chulaki, Anna; Hesse, Michael; Zenitani, Seiji

    2007-01-01

    We present first results of an investigation of the kinetic damping of Alfven wave turbulence. The methodology is based on a fully electromagnetic, three-dimensional, particle in cell code. The calculation is initialized by an Alfven wave spectrum. Subsequently, a cascade develops, and damping by coupling to both ions and electrons is observed. We discuss results of these calculations, and present first estimates of damping rates and of the effects of energy transfer on ion and electron distributions. The results pertain to solar wind heating and acceleration.

  12. On Alfven waves in the solar breeze

    International Nuclear Information System (INIS)

    The application to the solar wind motivates the consideration of Alfven waves in a radial background magnetic field and radial mean flow, in two cases, viz., with velocity and magnetic field perturbations along parallels, or also with perturbations along meridians, combined in the radial components of vorticity and electric current. In both cases the same second-order Alfven wave equation is obtained; it has, in general, two singularities. If the mean flow velocity is taken to be a power of radial distance, with exponent other than zero or unity, there is a transition layer. In general there is a second singularity, viz., a critical layer, where the Alfven speed equals the mean flow velocity. There is one exceptional case in which the critical layer does not exist, namely a homogeneous medium, for which the mean flow velocity decays on the inverse square of the radial distance, and then Alfven speed also decays in the same way, so that their ratio is a constant, leading to two possibilities: (i) the ratio is not unity, and the wave equation remains of the second-order; (ii) the wave equation becomes of first-order in the case the mean flow velocity and Alfven speed are equal everywhere, because then the waves can propagate only in one direction. Case (i) corresponds to Alfven waves in the solar breeze. Exact solutions of the wave equations are obtained for all values of the radius, as a single expression for the first-order wave equation, whereas for the second-order wave equation it is possible to obtain solutions for small and large radius; the transition level limits the radius of convergence of one of these solutions, but the two solutions together cover the full range of radial distances. The choices of boundary conditions are discussed and the wavefields plotted vs dimensionless distance for several values of the two dimensionless parameters of the problem, viz., the Alfven number and dimensionless frequency, which appear in one combination only. The

  13. Stationary nonlinear Alfven waves and solitons

    Science.gov (United States)

    Hada, T.; Kennel, C. F.; Buti, B.

    1989-01-01

    Stationary solutions of the derivative nonlinear Schroedinger equation are discussed and classified by using a pseudopotential formulation. The solutions consist of a rich family of nonlinear Alfven waves and solitons with parallel and oblique propagation directions. Expressions for the envelope and the phase of nonlinear waves with periodic envelope modulation, and 'hyperbolic' and 'algebraic' solitons are given. The propagation angle for the slightly modulated elliptic, periodic waves and for oblique solitons is evaluated.

  14. Effects of small wavenumber Alfven waves on particle acceleration

    International Nuclear Information System (INIS)

    Energetic charged particles are accelerated by turbulent Alfven waves via resonant interaction. We discuss effects of nonresonant Alfven waves on energy diffusion by using test particle simulations. When the Alfven waves are given at wavenumbers larger than the resonant wavenumber with small amplitude, simulated diffusion coefficient is similar to that by the quasi-linear theory. If the Alfven waves are added at wavenumbers smaller than the resonant wavenumber, it is found that the simulated diffusion coefficient exceeds the quasi-linear one and becomes larger with increasing the energy density of the nonresonant Alfven waves. (author)

  15. Alfven wave studies on a tokamak

    International Nuclear Information System (INIS)

    The continuum modes of the shear Alfven resonance are studied on the Tokapole II device, a small tokamak operated in a four node poloidal divertor configuration. A variety of antenna designs and the efficiency with which they deliver energy to the resonant layer are discussed. The spatial structure of the driven waves is studied by means of magnetic probes inserted into the current channel. In an attempt to optimize the coupling of energy in to the resonant layer, the angle of antenna currents with respect to the equilibrium field, antenna size, and plasma-to-antenna distance are varied. The usefulness of Faraday shields, particle shields, and local limiters are investigated. Antennas should be well shielded, either a dense Faraday shield or particle shield being satisfactory. The antenna should be large and very near to the plasma. The wave magnetic fields measured show a spatial resonance, the position of which varies with the value of the equilibrium field and mass density. They are polarized perpendicular to the equilibrium field. A wave propagates radially in to the resonant surface where it is converted to the shear Alfven wave. The signal has a short risetime and does not propagate far toroidally. These points are all consistent with a strongly damped shear Alfven wave. Comparisons of this work to theoretical predictions and results from other tokamaks are made

  16. Effect of the radial electric field, induced by Alfven waves, on transport processes in tokamaks

    International Nuclear Information System (INIS)

    We demonstrate that Alfven waves may be the convenient trigger for the formation and maintenance of edge and internal transport barriers due to their small radial localizations. Kinetic Alfven waves can also provide a mechanism for squeezing the banana orbits of ions in collisional plasmas of tokamaks. It is shown that the radial electric field, induced by Alfven waves, at some conditions has a nonlinear dependence on the radio-frequency absorbed power. The dependence of the ion heat conductivity and of the ion poloidal viscosity oil the radio-frequency absorbed power is obtained in this paper for tokamak plasmas with ion banana orbits squeezed by Alfven waves. Estimations of the proper absorbed power of Alfven waves in some tokamaks is about the level of absorbed power to be used in early fulfilled experiments. (author)

  17. Effect of the radial electric field, induced by Alfven waves, on transport processes in tokamaks

    International Nuclear Information System (INIS)

    We demonstrate that Alfven waves may be the convenient trigger for the formation and maintenance of edge and internal transport barriers due to their small radial localizations. Kinetic Alfven waves can also provide a mechanism for squeezing the banana orbits of ions in weekly collisional plasmas of tokamaks. It is shown that the radial electric field, induced by Alfven waves, at some conditions has a nonlinear dependence on the radio-frequency absorbed power. The dependence of the ion heat conductivity and of the ion poloidal viscosity on the radio-frequency absorbed power is obtained in this paper for tokamak plasmas with ion banana orbit squeezed by Alfven waves. Estimations of the proper absorbed power of Alfven waves in some tokamaks is about the level of absorbed power to be used in early fulfilled experiments. (author)

  18. KINETIC ALFVEN WAVES EXCITED BY OBLIQUE MAGNETOHYDRODYNAMIC ALFVEN WAVES IN CORONAL HOLES

    International Nuclear Information System (INIS)

    Kinetic Alfven waves (KAWs) are small-scale dispersive AWs that can play an important role in particle heating and acceleration of space and solar plasmas. An excitation mechanism for KAWs created by the coupling between large-scale oblique AWs and small-scale KAWs is presented in this paper. Taking into account both the collisional and Landau damping dissipations, the results show that the net growth rate of the excited KAWs increases with their perpendicular wavenumber kperpendicular and reaches maximum at λe kperpendicular ∼ 0.3, where λe is the electron inertial length. However, for KAWs with shorter perpendicular wavelengths, the net growth rate decreases rapidly due to dissipative effects. The evaluation of the threshold amplitude of the AW implies that for KAWs with λe kperpendicular e kperpendicular < 0.3 can be not only efficiently excited in the interplume region but also strongly dissipated in the dense plume due to the Landau damping.

  19. Effect of longitudinal modulation of Alfven wave filamentation

    International Nuclear Information System (INIS)

    The modulation of circularly polarized Alfven waves due to quasitransverse perturbations is addressed, and the nonlinear dynamics simulated numerically. In some instances, radial collapse (filamentation) of Alfven waves can be arrested by the magnetosonic waves stirred by the ponderomotive force. Such waves may, however, develop sharp fronts leading to strong hydrodynamic effects

  20. Excitation of Alfven Waves and Pulsar Radio Emission

    OpenAIRE

    Lyutikov, Maxim

    1999-01-01

    We analyze mechanisms of the excitation of Alfv\\'{e}n wave in pulsar magnetospheres as a possible source of pulsar radio emission generation. We find that Cherenkov excitation of obliquely propagating Alfv\\'{e}n waves is inefficient, while excitation at the anomalous cyclotron resonance by the particles from the primary beam and from the tail of the bulk distribution function may have a considerable growth rate. The cyclotron instability on Alfv\\'{e}n waves occurs in the kinetic regime still ...

  1. Analysis of Alfven Wave Activity in KSTAR Plasmas

    International Nuclear Information System (INIS)

    Full text: We report on evidence of neutral beam driven wave activity in KSTAR plasmas. In 2010 and 2011 campaigns KSTAR plasmas included 1MW of neutral beam heating, which provided drive for Alfvenic wave activity modes. Data from the 2010 campaign, which was fully analysed during 2011, identifies the 40 kHz magnetic fluctuations as a β-induced Alfven eignemode resonant with the q = 1 surface. Evidence is multiple fold: a Fourier mode analysis identifies the mode as n = 1. Electron cyclotron emission chords identify the q = 1 inversion radius. These constrain equilibrium reconstruction, and permit detailed MHD calculations using the global MHD stability code MISHKA. A scan of mode frequency near the q = 1 minimum of the continuum identifies a core localised n = 1 mode separated from the continuum. A complementary kinetic analysis, when coupled with ion and electron temperature measurements ratios obtain from crystallography, enables calculation of the frequency evolution - which is in agreement with observations. In 2011 a series of experiments were conducted to scope Alfven excitation using NBI and ECRH heating as a function of field strength and plasma current. In these experiments plasmas with toroidal current up to 600 kA were generated with 1.5 MW of NBI heating and up to 120 kW of co or counter ECRH, and the field strength varied from 1.7 T to 2 T. Spectral and mode number analysis of the magnetics data identifies 150 - 250 kHz coherent activity with a toroidal mode number of n = 1. Assuming a poloidal mode number of m = 1, we have computed the evolution of the toroidal Alfven eigenmode (TAE) middle of the gap frequency, and compared the frequency evolution to magnetic spectrograms. While the frequency of the mode is above the Nyquist frequency, the aliased frequency tracks the observations to within 20%, providing some confidence of a TAE interpretation. Finally, we also report evidence of ion fishbone activity. (author)

  2. Alfven Wave Collisions, The Fundamental Building Block of Plasma Turbulence IV: Laboratory Experiment

    CERN Document Server

    Drake, D J; Howes, G G; Kletzing, C A; Skiff, F; Carter, T A; Auerbach, D W

    2013-01-01

    Turbulence is a phenomenon found throughout space and astrophysical plasmas. It plays an important role in solar coronal heating, acceleration of the solar wind, and heating of the interstellar medium. Turbulence in these regimes is dominated by Alfven waves. Most turbulence theories have been established using ideal plasma models, such as incompressible MHD. However, there has been no experimental evidence to support the use of such models for weakly to moderately collisional plasmas which are relevant to various space and astrophysical plasma environments. We present the first experiment to measure the nonlinear interaction between two counterpropagating Alfven waves, which is the building block for astrophysical turbulence theories. We present here four distinct tests that demonstrate conclusively that we have indeed measured the daughter Alfven wave generated nonlinearly by a collision between counterpropagating Alfven waves.

  3. Solitary kinetic Alfven waves in adiabatic process

    International Nuclear Information System (INIS)

    Solitary kinetic Alfven waves (SKAWs) have been an important subject in the field of space plasma physics because of their nonzero parallel electrical field and density fluctuations. Under different thermodynamic processes, SKAWs, within the limit of small amplitude, are studied analytically and numerically using the Sagdeev potential method. The results show that the width of the solitary structures is larger and the amplitude of the density humps is smaller under constant entropy than those under constant temperature with other relevant parameters being the same. The perturbed electromagnetic fields Ex, By, and Ez are also studied further.

  4. Nonlinear propagation of short wavelength drift-Alfven waves

    DEFF Research Database (Denmark)

    Shukla, P. K.; Pecseli, H. L.; Juul Rasmussen, Jens

    1986-01-01

    Making use of a kinetic ion and a hydrodynamic electron description together with the Maxwell equation, the authors derive a set of nonlinear equations which governs the dynamics of short wavelength ion drift-Alfven waves. It is shown that the nonlinear drift-Alfven waves can propagate as two...

  5. HLL Riemann Solvers and Alfven Waves in Black Hole Magnetospheres

    CERN Document Server

    Punsly, Brian; Kim, Jinho; Garain, Sudip

    2016-01-01

    In the magnetosphere of a rotating black hole, an inner Alfven critical surface (IACS) must be crossed by inflowing plasma. Inside the IACS, Alfven waves are inward directed toward the black hole. The majority of the proper volume of the active region of spacetime (the ergosphere) is inside of the IACS. The charge and the totally transverse momentum flux (the momentum flux transverse to both the wave normal and the unperturbed magnetic field) are both determined exclusively by the Alfven polarization. However, numerical simulations of black hole magnetospheres are often based on 1-D HLL Riemann solvers that readily dissipate Alfven waves. Elements of the dissipated wave emerge in adjacent cells regardless of the IACS, there is no mechanism to prevent Alfvenic information from crossing outward. Thus, it is unclear how simulated magnetospheres attain the substantial Goldreich-Julian charge density associated with the rotating magnetic field. The HLL Riemann solver is also notorious for producing large recurring...

  6. Experiments on linear high beta helical axis stellarators to study simulated toroidal effects and Alfven-wave heating: [Annual] progress report No. 1, February 16, 1987-November 15, 1987

    International Nuclear Information System (INIS)

    This paper discusses experiments on linear high beta helical axis stellarators. Experiments considered are: formation of linear high beta heliac plasma configurations; Alfven wave heating in a straight tube and in a linear high beat stellarator; shifted hardcore heliac studies; a system for measuring the timing of high-current switches in a pulsed high voltage fusion experiment; HBQM general refurbishment; and proposed experiment on excitation of the m = 1 tilt mode in field-reversed configurations

  7. Emission of Alfven Waves by Planets in Close Orbits

    Science.gov (United States)

    MacGregor, Keith B.; Pinsonneault, M. H.

    2011-01-01

    We examine the electrodynamics of a conducting planet orbiting within a magnetized wind that emanates from its parent star. When the orbital motion differs from corotation with the star, an electric field exists in the rest frame of the planet, inducing a charge separation in its ionosphere. Because the planet is immersed in a plasma, this charge can flow away from it along the stellar magnetic field lines it successively contacts in its orbit. For sufficiently rapid orbital motion, a current system can be formed that is closed by Alfvenic disturbances that propagate along field lines away from the planet. Using a simple model for the wind from a Sun-like star, we survey the conditions under which Alfven wave emission can occur, and estimate the power radiated in the form of linear waves for a range of stellar, planetary, and wind properties. For a Jupiter-like planet in a close (a type star, the emitted wave power can be as large as 1027 erg/s. While only a small influence on the planet's orbit, a wave power of this magnitude may have consequences for wind dynamics and localized heating of the stellar atmosphere. NCAR is sponsored by the NSF.

  8. Inertial Alfven waves in an inhomogeneous bi-Maxwellian plasma

    International Nuclear Information System (INIS)

    The Vlasov kinetic equation is solved using gyrokinetic theory and the dielectric tensor for non-relativistic, magnetized, bi-Maxwellian plasmas is calculated. A generalized dispersion relation for kinetic Alfven waves is derived taking into account the density inhomogeneity and temperature anisotropy. The modified dispersion relation thus obtained is then used to examine the propagation characteristics of the kinetic Alfven waves in the inertial regime. The importance of density inhomogeneity and temperature anisotropy for Solar corona is highlighted. The growth rate of the inertial Alfven wave proves that density inhomogeneity acts as a source of free energy.

  9. Preliminary results on Alfven wave system in the TCABR tokamak

    International Nuclear Information System (INIS)

    A brief review of the Alfven Wave Excitation System (AWES) designed for the TCABR tokamak and the first experimental results on RF plasma heating are presented. One of four antenna modules has been completely installed in the vacuum chamber and the initial experiments were carried out in the low power regime using the four-phase RF generator. The main objectives were the antenna tuning according to the typical plasma parameters of TCABR and the evaluation of the antenna parasitic loading, as well as the calibration of the RF diagnostic tools in real discharge conditions. The first results have been obtained with standard diagnostics and with the RF signals measured using high sampling rate digital oscilloscopes. They showed that daily antenna cleaning and correct wave helicity excitation reduce significantly the parasitic loading and are crucial for efficient plasma coupling

  10. Experiments on linear high beta helical axis stellarators to study simulated toroidal effects and Alfven-Wave heating

    International Nuclear Information System (INIS)

    This report discusses the following topics: Nonaxisymmetric radio- frequency heating in an l = 1 stellarator and in a linear plasma column; measurement of induced current in a hardcore theta pinch; externally driven tilt mode study on an FRC; elimination of induced plasma current in a hardcore theta pinch; and simulated toroidicity studies

  11. Experiments on linear high beta helical axis stellarators to study simulated toroidal effects and Alfven-wave heating

    International Nuclear Information System (INIS)

    This paper discusses induced axial current studies in a hardcore Theta-Pinch; nonaxisymmetric RF heating of a high-Beta plasma column; formation of Axisymmetric hardcore theta pinches with notched hardcore current; and externally driven till made experiments on the high-beta Q machine field reversed configuration

  12. Generation of coherent wave packets of kinetic Alfven waves in solar plasmas

    International Nuclear Information System (INIS)

    This work presents the numerical simulations to study the filamentation of kinetic Alfven waves in solar plasmas. Using the modified nonlinear Schroedinger equation model, we study the effect of changing the initial perturbation on filament formation and their nonlinear dynamics. The spectral indices of the power spectrum are calculated with different initial conditions of the simulations. The relevance of the present investigation in coronal heating and solar wind acceleration/turbulence is also pointed out

  13. Alfven wave. [Book on linear and nonlinear properties for fusion applications

    Energy Technology Data Exchange (ETDEWEB)

    Hasegawa, A.; Uberoi, C.

    1978-11-01

    Seven chapters are included. Chapters 1 and 2 introduce the Alfven wave and describe its linear properties in a homogeneous medium. Chapters 3 and 4 cover the effects of inhomogeneities on these linear properties. Particular emphasis is placed on the appearance of a continuum spectrum and the associated absorption of the Alfven wave which arise due to the inhomogeneity. The explanation of the physical origin of absorption is given using kinetic theory. Chapter 5 is devoted to the associated plasma instabilities. Nonlinear effects discussed in Chapter 6 include quasilinear diffusion, decay, a solitary wave, and a modulational instability. The principles of Alfven wave heating, a design example and present-day experimental results are described in Chapter 7.

  14. On the origin of solar wind. Alfven waves induced jump of coronal temperature

    CERN Document Server

    Mishonov, T M; Maneva, Y G

    2007-01-01

    Absorbtion of Alfven waves is considered as the main mechanism of heating of solar corona. It is concluded that the sharp increase of the plasma temperature by two orders of magnitude is related to a self-induced opacity with respect to Alfven waves. The maximal frequency for propagation of Alfven waves is determined by the strongly temperature dependent kinematic viscosity. In such a way the temperature jump is due to absorption of high frequency Alfven waves in a narrow layer above the solar surface. There is calculated the dissipated in this layer power, which blows up the plasma and gives birth to the solar wind. A model short wave-length (WKB) evaluation takes into account the 1/f^2 frequency dependance of the transversal magnetic field and velocity spectral densities. Such spectral densities agree with an old magnetometer's data taken by Voyager 1 and recent theoretical calculations in the framework of Langevin-Burgers MHD. The present theory predicts existence of intensive high frequency Alfven waves i...

  15. Coronal heating by the resonant absorption of Alfven waves - Importance of the global mode and scaling laws

    Science.gov (United States)

    Steinolfson, Richard S.; Davila, Joseph M.

    1993-01-01

    Numerical simulations of the MHD equations for a fully compressible, low-beta, resistive plasma are used to study the resonance absorption process for the heating of coronal active region loops. Comparisons with more approximate analytic models show that the major predictions of the analytic theories are, to a large extent, confirmed by the numerical computations. The simulations demonstrate that the dissipation occurs primarily in a thin resonance layer. Some of the analytically predicted features verified by the simulations are (a) the position of the resonance layer within the initial inhomogeneity; (b) the importance of the global mode for a large range of loop densities; (c) the dependence of the resonance layer thickness and the steady-state heating rate on the dissipation coefficient; and (d) the time required for the resonance layer to form. In contrast with some previous analytic and simulation results, the time for the loop to reach a steady state is found to be the phase-mixing time rather than a dissipation time. This disagreement is shown to result from neglect of the existence of the global mode in some of the earlier analyses. The resonant absorption process is also shown to behave similar to a classical driven harmonic oscillator.

  16. Interplanetary Alfven waves and auroral (substorm) activity: IMP 8

    International Nuclear Information System (INIS)

    Almost year of IMP 8 interplanetary magnetic field and plasma data (Days 1-312, 1979) have been examined to determine the interplanetary causes of geomagnetic AE activity. The nature of the interplanetary medium (Alfvenic or non-Alfvenic) and the B2 correlation with AE were examined over 12-hour increments throughout the study. It is found that Alfvenic wave intervals (defined as Vx-Bx cross-correlation coefficients of >0.6) are present over 60% of the time and the southward component of the Alfven waves is well correlated with AE (average peak correlation coefficient 0.62), with a median lag of 43 min. The most probable delay of AE from Bs is considerably shorter, about 20-25 min. Southward magnetic fields during non-Alfvenic intervals (Vx-Bx cross-correlation coefficients of s were variable from event to event (and at different times within the Alfven wave train), ranging from 45 min to as little as 0 min. The cause of this variable delay is somewhat surprising and is not presently well understood

  17. Nonlinear coherent structures of Alfven wave in a collisional plasma

    International Nuclear Information System (INIS)

    Low-frequency Magneto Hydrodynamic waves in general and Alfv´en wave, in particular, occurs in various physical problems starting from laboratory to space plasma. These low frequency disturbances make the magnetic fluctuations large enough so that nonlinear coupling becomes finite. Among these low-frequency waves, nonlinear Alfv´en wave has become a topic of intense research due to its applications in various physical processes, related to particle energization in magnetized plasma, self-modulation in strongly magnetized plasma, tokamak plasma heating, interplanetary shocks, turbulence etc. In the present work, we have investigated weakly nonlinear Alfv´en wave dynamics in the framework of Lagrangian two-fluid theory in a compressible cold magnetized plasma in presence of finite electron inertia effect. The electron-ion collision induced dissipation effect is also taken into account. In the finite amplitude limit, we have shown that the collisionless Alfv´en wave is governed by a modified Korteweg-de Vries (mKdV) equation. In presence of collision it becomes a modified Korteweg-de Vries -Burgers (mKdVB) equation, where the electron inertia is found to act as a dispersive effect and the electron-ion collision serves as a dissipation which is responsible for the Burgers term. In the long wavelength limit, we have also investigated another important physical phenomenon, known as the wave modulation instability. The dynamics of this modulated wave is shown to be governed by a nonlinear Schrödinger equation (NLSE) with a linear damping term arising due to electron-ion collision. These two nonlinear equations are analyzed by means of analytical and numerical simulation to elucidate the various aspects of the phase-space dynamics of the nonlinear wave. Both the results reveal that nonlinear Alfven wave exhibits shock, dissipative envelope and breather like structures. Numerical simulation also predicts the formation of Alv´enic rogue wave and giant breathers

  18. Stable Alfven wave dynamo action in the reversed field pinch

    International Nuclear Information System (INIS)

    Recent advances in linear resistive MHD stability analysis are used to calculate the quasi-linear dynamo mean electromotive force of Alfven waves. This emf is incorporated into a one-dimensional transport and mean-field evolution code. The changing equilibrium is then fed back to the stability code to complete a computational framework that self-consistently evaluates a dynamic plasma dynamo. Static quasi-linear Alfven wave calculations have shown that dynamo emfs on the order of eta vector J are possible. This suggested a possible explanation of RFP behavior and a new (externally driven) mechanism for extending operation and controlling field profiles (possibly reducing plasma transport). This thesis demonstrates that the dynamo emf can quickly induce plasma currents whose emf cancels the dynamo effect. This thesis also contains extensive studies of resistive Alfven wave properties. This includes behavior versus spectral location, magnetic Reynolds number and wave number

  19. ALFVEN WAVES IN A PARTIALLY IONIZED TWO-FLUID PLASMA

    Energy Technology Data Exchange (ETDEWEB)

    Soler, R.; Ballester, J. L.; Terradas, J. [Departament de Fisica, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain); Carbonell, M., E-mail: roberto.soler@uib.es, E-mail: joseluis.ballester@uib.es, E-mail: jaume.terradas@uib.es, E-mail: marc.carbonell@uib.es [Departament de Matematiques i Informatica, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain)

    2013-04-20

    Alfven waves are a particular class of magnetohydrodynamic waves relevant in many astrophysical and laboratory plasmas. In partially ionized plasmas the dynamics of Alfven waves is affected by the interaction between ionized and neutral species. Here we study Alfven waves in a partially ionized plasma from the theoretical point of view using the two-fluid description. We consider that the plasma is composed of an ion-electron fluid and a neutral fluid, which interact by means of particle collisions. To keep our investigation as general as possible, we take the neutral-ion collision frequency and the ionization degree as free parameters. First, we perform a normal mode analysis. We find the modification due to neutral-ion collisions of the wave frequencies and study the temporal and spatial attenuation of the waves. In addition, we discuss the presence of cutoff values of the wavelength that constrain the existence of oscillatory standing waves in weakly ionized plasmas. Later, we go beyond the normal mode approach and solve the initial-value problem in order to study the time-dependent evolution of the wave perturbations in the two fluids. An application to Alfven waves in the low solar atmospheric plasma is performed and the implication of partial ionization for the energy flux is discussed.

  20. Nonlinear Alfven waves and solitons in cold plasma

    International Nuclear Information System (INIS)

    A finite-zone sector for the derivative nonlinear Schroedinger equation, which describes nonlinear small-amplitude. Alfven waves in the long-wave approximation, is investigated. The formulas for periodic one-phase and one-soliton solutions and the general formula for an n-soliton solution envelope are obtained

  1. Oxygen Ion Heat Rate within Alfvenic Turbulence in the Cusp

    Science.gov (United States)

    Coffey, Victoria N.; Singh, Nagendra; Chandler, Michael O.

    2009-01-01

    The role that the cleft/cusp has in ionosphere-magnetosphere coupling makes it a dynamic and important region. It is directly exposed to the solar wind, making it possible for the entry of electromagnetic energy and precipitating electrons and ions from dayside reconnection and other dayside events. It is also a significant source of ionospheric plasma, contributing largely to the mass loading of the magnetosphere with large fluxes of outflowing ions. Crossing the cusp/cleft near 5100 km, the Polar instruments observe the common correlation of downward Poynting flux, ion energization, soft electron precipitation, broadband extremely low-frequency (BB-ELF) emissions, and density depletions. The dominant power in the BB-ELF emissions is now identified to be from spatially broad, low frequency Alfv nic structures. For a cusp crossing, we determine using the Electric Field Investigation (EFI), that the electric and magnetic field fluctuations are Alfv nic and the electric field gradients satisfy the inequality for stochastic acceleration. With all the Polar 1996 horizontal crossings of the cusp, we determine the O+ heating rate using the Thermal Ion Dynamics Experiment (TIDE) and Plasma Wave Investigation (PWI). We then compare this heating rate to other heating rates assuming the electric field gradient criteria exceeds the limit for stochastic acceleration for the remaining crossings. The comparison suggests that a stochastic acceleration mechanism is operational and the heating is controlled by the transverse spatial scale of the Alfvenic waves.

  2. Resonant Alfven wave instabilities driven by streaming fast particles

    International Nuclear Information System (INIS)

    A plasma simulation code is used to study the resonant interactions between streaming ions and Alfven waves. The medium which supports the Alfven waves is treated as a single, one-dimensional, ideal MHD fluid, while the ions are treated as kinetic particles. The code is used to study three ion distributions: a cold beam; a monoenergetic shell; and a drifting distribution with a power-law dependence on momentum. These distributions represent: the field-aligned beams upstream of the earth's bow shock; the diffuse ions upstream of the bow shock; and the cosmic ray distribution function near a supernova remnant shock. 92 refs., 31 figs., 12 tabs

  3. Quantum effects on compressional Alfven waves in compensated semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Amin, M. R. [Department of Electronics and Communications Engineering, East West University, Aftabnagar, Dhaka 1212 (Bangladesh)

    2015-03-15

    Amplitude modulation of a compressional Alfven wave in compensated electron-hole semiconductor plasmas is considered in the quantum magnetohydrodynamic regime in this paper. The important ingredients of this study are the inclusion of the particle degeneracy pressure, exchange-correlation potential, and the quantum diffraction effects via the Bohm potential in the momentum balance equations of the charge carriers. A modified nonlinear Schrödinger equation is derived for the evolution of the slowly varying amplitude of the compressional Alfven wave by employing the standard reductive perturbation technique. Typical values of the parameters for GaAs, GaSb, and GaN semiconductors are considered in analyzing the linear and nonlinear dispersions of the compressional Alfven wave. Detailed analysis of the modulation instability in the long-wavelength regime is presented. For typical parameter ranges of the semiconductor plasmas and at the long-wavelength regime, it is found that the wave is modulationally unstable above a certain critical wavenumber. Effects of the exchange-correlation potential and the Bohm potential in the wave dynamics are also studied. It is found that the effect of the Bohm potential may be neglected in comparison with the effect of the exchange-correlation potential in the linear and nonlinear dispersions of the compressional Alfven wave.

  4. Kinetic Alfven Waves at the Magnetopause-Mode Conversion, Transport and Formation of LLBL; TOPICAL

    International Nuclear Information System (INIS)

    At the magnetopause, large amplitude, low-frequency (ULF), transverse MHD waves are nearly always observed. These waves likely result from mode conversion of compressional MHD waves observed in the magnetosheath to kinetic Alfven waves at the magnetopause where there is a steep gradient in the Alfven velocity[Johnson and Cheng, Geophys. Res. Lett. 24 (1997) 1423]. The mode-conversion process can explain the following wave observations typically found during satellite crossings of the magnetopause: (1) a dramatic change in wave polarization from compressional in the magnetosheath to transverse at the magnetopause, (2) an amplification of wave amplitude at the magnetopause, (3) a change in Poynting flux from cross-field in the magnetosheath to field-aligned at the magnetopause, and (4) a steepening in the wave power spectrum at the magnetopause. We examine magnetic field data from a set of ISEE1, ISEE2, and WIND magnetopause crossings and compare with the predictions of theoretical wave solutions based on the kinetic-fluid model with particular attention to the role of magnetic field rotation across the magnetopause. The results of the study suggest a good qualitative agreement between the observations and the theory of mode conversion to kinetic Alfven waves. Because mode-converted kinetic Alfven waves readily decouple particles from the magnetic field lines, efficient quasilinear transport (D(approx) 109m2/s) can occur. Moreover, if the wave amplitude is sufficiently large (Bwave/B0 and gt; 0.2) stochastic particle transport also occurs. This wave-induced transport can lead to significant heating and particle entry into the low latitude boundary layer across closed field lines.At the magnetopause, large amplitude, low-frequency (ULF), transverse MHD waves are nearly always observed. These waves likely result from mode conversion of compressional MHD waves observed in the magnetosheath to kinetic Alfven waves at the magnetopause where there is a steep gradient in

  5. Shear Alfven wave excitation by direct antenna coupling and fast wave resonant mode conversion

    International Nuclear Information System (INIS)

    Antenna coupling to the shear Alfven wave by both direct excitation and fast wave resonant mode conversion is modelled analytically for a plasma with a one dimensional linear density gradient. We demonstrate the existence of a shear Alfven mode excited directly by the antenna. For localised antennas, this mode propagates as a guided beam along the steady magnetic field lines intersecting the antenna. Shear Alfven wave excitation by resonant mode conversion of a fast wave near the Alfven resonance layer is also demonstrated and we prove that energy is conserved in this process. We compare the efficiency of these two mechanisms of shear Alfven wave excitation and present a simple analytical formula giving the ratio of the coupled powers. Finally, we discuss the interpretation of some experimental results. 45 refs., 7 figs

  6. Heat Waves

    Science.gov (United States)

    Heat Waves Dangers we face during periods of very high temperatures include: Heat cramps: These are muscular pains and spasms due ... that the body is having trouble with the heat. If a heat wave is predicted or happening… - ...

  7. Recent Results of Alfven Wave Studies in TCABR

    International Nuclear Information System (INIS)

    The results on comparative studies of Alfven wave plasma heating by two different antenna types in TCABR are presented. Emphasis is placed on the excited wave spectra and parasitic coupling with the edge plasma. The antenna modules have two groups of RF current-carrying straps separated by a toroidal angle of approximately 22 deg. In type I antenna, each group consists of two circular loops that are cut in two half-turn windings. The feeders of each loop pair are rotated 90 deg. in the poloidal direction with respect to each other, to decrease the mutual coupling between them and make it possible to excite single helicity plasma modes (M=+1 or M=-1). In type II antenna, each group consists of two poloidal straps located at the low-magnetic-field side of the vacuum chamber. The poloidal extension of each strap is around 90 deg. and the angle between straps is also of the same value. In both antenna types, the straps have side protectors of boron nitride. Initial experiments indicate that the parasitic interaction with the edge plasma is quite different for the two antennae. Also the first type has larger self-inductance, making it more difficult to deliver high currents to the antenna without increasing the dynamic polarization voltage up to breakdown limits. Results on the excited spectrum and floating potential at the plasma edge are presented

  8. Overdamped Alfven waves due to ion-neutral collisions in the solar chromosphere

    CERN Document Server

    Soler, R; Zaqarashvili, T V

    2014-01-01

    Alfvenic waves are ubiquitous in the solar atmosphere and their dissipation may play an important role in atmospheric heating. In the partially ionized solar chromosphere, collisions between ions and neutrals are an efficient dissipative mechanism for Alfven waves with frequencies near the ion-neutral collision frequency. The collision frequency is proportional to the ion-neutral collision cross section for momentum transfer. Here, we investigate Alfven wave damping as a function of height in a simplified chromospheric model and compare the results for two sets of collision cross sections, namely those of the classic hard-sphere model and those based on recent quantum-mechanical computations. We find important differences between the results for the two sets of cross sections. There is a critical interval of wavelengths for which impulsively excited Alfven waves are overdamped as a result of the strong ion-neutral dissipation. The critical wavelengths are in the range from 1 km to 50 km for the hard-sphere cr...

  9. Roles of Fast-Cyclotron and Alfven-Cyclotron Waves for the Multi-Ion Solar Wind

    OpenAIRE

    Xiong, Ming; Li, Xing

    2012-01-01

    Using linear Vlasov theory of plasma waves and quasi-linear theory of resonant wave-particle interaction, the dispersion relations and the electromagnetic field fluctuations of fast and Alfven waves are studied for a low-beta multi-ion plasma in the inner corona. Their probable roles in heating and accelerating the solar wind via Landau and cyclotron resonances are quantified. We assume that (1) low-frequency Alfven and fast waves have the same spectral shape and the same amplitude of power s...

  10. Nonlinear absorption of Alfven wave in dissipative plasma

    Energy Technology Data Exchange (ETDEWEB)

    Taiurskii, A. A., E-mail: tayurskiy2001@mail.ru; Gavrikov, M. B., E-mail: nadya-p@cognitive.ru [Keldysh Institute of Applied Mathematics, Russian Academy of Sciences, 4 Miusskaya sq. Moscow 125047 (Russian Federation)

    2015-10-28

    We propose a method for studying absorption of Alfven wave propagation in a homogeneous non-isothermal plasma along a constant magnetic field, and relaxation of electron and ion temperatures in the A-wave. The absorption of a A-wave by the plasma arises due to dissipative effects - magnetic and hydrodynamic viscosities of electrons and ions and their elastic interaction. The method is based on the exact solution of two-fluid electromagnetic hydrodynamics of the plasma, which for A-wave, as shown in the work, are reduced to a nonlinear system of ordinary differential equations.

  11. Nonlinear absorption of Alfven wave in dissipative plasma

    International Nuclear Information System (INIS)

    We propose a method for studying absorption of Alfven wave propagation in a homogeneous non-isothermal plasma along a constant magnetic field, and relaxation of electron and ion temperatures in the A-wave. The absorption of a A-wave by the plasma arises due to dissipative effects - magnetic and hydrodynamic viscosities of electrons and ions and their elastic interaction. The method is based on the exact solution of two-fluid electromagnetic hydrodynamics of the plasma, which for A-wave, as shown in the work, are reduced to a nonlinear system of ordinary differential equations

  12. Plastic damping of Alfv\\'en waves in magnetar flares and delayed afterglow emission

    CERN Document Server

    Li, Xinyu

    2015-01-01

    Magnetar flares generate Alfv\\'en waves bouncing in the closed magnetosphere with energy up to $\\sim 10^{46}$ erg. We show that on a 10-ms timescale the waves are transmitted into the star and form a compressed packet of high energy density. This packet strongly shears the stellar crust and initiates a plastic flow, heating the crust and melting it hundreds of meters below the surface. A fraction of the deposited plastic heat is eventually conducted to the stellar surface, contributing to the surface afterglow months to years after the flare. A large fraction of heat is lost to neutrino emission or conducted into the core of the neutron star.

  13. Simulation of the interaction between Alfven waves and fast particles

    International Nuclear Information System (INIS)

    There is a wide variety of Alfven waves in tokamak and stellarator plasmas. While most of them are damped, some of the global eigenmodes can be driven unstable when they interact with energetic particles. By coupling the MHD code CKA with the gyrokinetic code EUTERPE, a hybrid kinetic-MHD model is created to describe this wave-particle interaction in stellarator geometry. In this thesis, the CKA-EUTERPE code package is presented. This numerical tool can be used for linear perturbative stability analysis of Alfven waves in the presence of energetic particles. The equations for the hybrid model are based on the gyrokinetic equations. The fast particles are described with linearized gyrokinetic equations. The reduced MHD equations are derived by taking velocity moments of the gyrokinetic equations. An equation for describing the Alfven waves is derived by combining the reduced MHD equations. The Alfven wave equation can retain kinetic corrections. Considering the energy transfer between the particles and the waves, the stability of the waves can be calculated. Numerically, the Alfven waves are calculated using the CKA code. The equations are solved as an eigenvalue problem to determine the frequency spectrum and the mode structure of the waves. The results of the MHD model are in good agreement with other sophisticated MHD codes. CKA results are shown for a JET and a W7-AS example. The linear version of the EUTERPE code is used to study the motion of energetic particles in the wavefield with fixed spatial structure, and harmonic oscillations in time. In EUTERPE, the gyrokinetic equations are discretized with a PIC scheme using the delta-f method, and both full orbit width and finite Larmor radius effects are included. The code is modified to be able to use the wavefield calculated externally by CKA. Different slowing-down distribution functions are also implemented. The work done by the electric field on the particles is measured to calculate the energy transfer

  14. Looking for Cosmological Alfven Waves in WMAP Data

    OpenAIRE

    Chen, Gang; Mukherjee, Pia; Kahniashvili, Tina; Ratra, Bharat; Wang, Yun

    2004-01-01

    A primordial cosmological magnetic field induces and supports vorticity or Alfven waves, which in turn generate cosmic microwave background (CMB) anisotropies. A homogeneous primordial magnetic field with fixed direction induces correlations between the $a_{l-1,m}$ and $a_{l+1,m}$ multipole coefficients of the CMB temperature anisotropy field. We discuss the constraints that can be placed on the strength of such a primordial magnetic field using CMB anisotropy data from the WMAP experiment. W...

  15. Resonant energy conversion of 3-minute intensity oscillations into Alfven waves in the solar atmosphere

    CERN Document Server

    Kuridze, D

    2007-01-01

    Nonlinear coupling between 3-minute oscillations and Alfven waves in the solar lower atmosphere is studied. 3-minute oscillations are considered as acoustic waves trapped in a chromospheric cavity and oscillating along transversally inhomogeneous vertical magnetic field. It is shown that under the action of the oscillations the temporal dynamics of Alfven waves is governed by Mathieu equation. Consequently, the harmonics of Alfven waves with twice period and wavelength of 3-minute oscillations grow exponentially in time near the layer where the sound and Alfven speeds equal. Thus the 3-minute oscillations are resonantly absorbed by pure Alfven waves near this resonant layer. The resonant Alfven waves may penetrate into the solar corona taking energy from the chromosphere. Therefore the layer c_s=v_A may play a role of energy channel for otherwise trapped acoustic oscillations.

  16. Torsional Alfv\\'en waves in solar partially ionized plasma: effects of neutral helium and stratification

    OpenAIRE

    Zaqarashvili, T. V.; Khodachenko, M. L.; Soler, R.

    2012-01-01

    Ion-neutral collisions may lead to the damping of Alfven waves in chromospheric and prominence plasmas. Neutral helium atoms enhance the damping in certain temperature interval, where the ratio of neutral helium and neutral hydrogen atoms is increased. Therefore, the height-dependence of ionization degrees of hydrogen and helium may influence the damping rate of Alfven waves. We aim to study the effect of neutral helium in the damping of Alfven waves in stratified partially ionized plasma of ...

  17. Enhanced phase mixing of Alfv\\'en waves propagating in stratified and divergent coronal structures

    OpenAIRE

    Smith, P. D.; Tsiklauri, D.; Ruderman, M. S.

    2007-01-01

    Corrected analytical solutions describing the enhanced phase mixing of Alfven waves propagating in divergent stratified coronal structures are presented. These show that the enhanced phase mixing mechanism can dissipate Alfven waves at heights less than half that is predicted by the previous analytical solutions. The enhanced phase mixing of 0.1 Hz harmonic Alfven waves propagating in strongly divergent, H_b=5 Mm, stratified coronal structures, H_rho=50 Mm, can fulfill 100% of an active regio...

  18. Alfv\\'en waves in simulations of solar photospheric vortices

    CERN Document Server

    Shelyag, S; Reid, A; Mathioudakis, M

    2013-01-01

    Using advanced numerical magneto-hydrodynamic simulations of the magnetised solar photosphere, including non-grey radiative transport and a non-ideal equation of state, we analyse plasma motions in photospheric magnetic vortices. We demonstrate that apparent vortex-like motions in photospheric magnetic field concentrations do not exhibit "tornado"-like behaviour or a "bath-tub" effect. While at each time instance the velocity field lines in the upper layers of the solar photosphere show swirls, the test particles moving with the time-dependent velocity field do not demonstrate such structures. Instead, they move in a wave-like fashion with rapidly changing and oscillating velocity field, determined mainly by magnetic tension in the magnetised intergranular downflows. Using time-distance diagrams, we identify horizontal motions in the magnetic flux tubes as torsional Alfv\\'en perturbations propagating along the nearly vertical magnetic field lines with local Alfv\\'en speed.

  19. The effect of compressibility on the Alfven spatial resonance heating

    International Nuclear Information System (INIS)

    The effect of compressibility of magnetic field line on the damping rate of Alfven spatial resonance heating for a high beta plasma (Kinetic pressure/magnetic pressure) was analysed, using the ideal MHD (Magnetohydrodynamic) model in cylindrical geometry for a diffuse θ-pinch with conducting wall. The dispersion relation was obtained solving the equation of motion in the plasma and vacuum regions together with boundary conditions. (Author)

  20. Transition of toroidal Alfven eigenmode to global Alfven eigenmode in CHS heliotron/torsatron plasmas heated by neutral beam injection

    International Nuclear Information System (INIS)

    A transition of a core localized type toroidal Alfven eigenmode with n 1 toroidal mode number to two n = 1 global Alfven eignemodes was observed in NBI-heated plasmas in the Compact Helical System (CHS) heliotron/torsatron. This transition phenomenon is interpreted based on the temporal evolution of the rotational transform near the plasma center caused by the increased in the beam-driven current. (author)

  1. Modulational instability of finite-amplitude, circularly polarized Alfven waves

    Science.gov (United States)

    Derby, N. F., Jr.

    1978-01-01

    The simple theory of the decay instability of Alfven waves is strictly applicable only to a small-amplitude parent wave in a low-beta plasma, but, if the parent wave is circularly polarized, it is possible to analyze the situation without either of these restrictions. Results show that a large-amplitude circularly polarized wave is unstable with respect to decay into three waves, one longitudinal and one transverse wave propagating parallel to the parent wave and one transverse wave propagating antiparallel. The transverse decay products appear at frequencies which are the sum and difference of the frequencies of the parent wave and the longitudinal wave. The decay products are not familiar MHD modes except in the limit of small beta and small amplitude of the parent wave, in which case the decay products are a forward-propagating sound wave and a backward-propagating circularly polarized wave. In this limit the other transverse wave disappears. The effect of finite beta is to reduce the linear growth rate of the instability from the value suggested by the simple theory. Possible applications of these results to the theory of the solar wind are briefly touched upon.

  2. Characteristics of Short-wavelength Oblique Alfven and Slow waves

    CERN Document Server

    Zhao, J S; Yu, M Y; Lu, J Y; Wu, D J

    2014-01-01

    Linear properties of kinetic Alfv\\'en waves (KAWs) and kinetic slow waves (KSWs) are studied in the framework of two-fluid magnetohydrodynamics. We obtain the wave dispersion relations that are valid in a wide range of the wave frequency {\\omega} and plasma-to-magnetic pressure ratio {\\beta}. The KAW frequency can reach and exceed the ion cyclotron frequency at ion kinetic scales, whereas the KSW frequency remains sub-cyclotron. At {\\beta}\\sim1, the plasma and magnetic pressure perturbations of both modes are in anti-phase, so that there is nearly no total pressure perturbations. However, these modes exhibit several different properties. At high {\\beta}, the electric field polarization of KAW and KSW is opposite at the ion gyroradius scale, where KAWs are polarized in sense of electron gyration (right-hand polarized) and KSWs are left-hand polarized. The magnetic helicity {\\sigma}\\sim1 for KAWs and {\\sigma}\\sim-1 for KSWs, and the ion Alfv\\'en ratio R_{Ai}\\ll 1 for KAWs and R_{Ai}\\gg 1 for KSWs. We also found...

  3. Interplanetary Alfven waves inducing ionospheric disturbances observed by GPS data

    International Nuclear Information System (INIS)

    Complete text of publication follows. Interplanetary Alfven waves appear in satellite data as high-amplitude, fast oscillations in the interplanetary magnetic field and solar wind velocity components. The waves are more often present in high speed solar wind streams emanating from coronal holes. For a long time, these Alfven waves were not believed as able to produce geomagnetic responses due to the absence of a strong and sustained southward Bz (Bs) interplanetary magnetic field. But in 1987, Tsurutani and Gonzalez showed that these structures were responsible by intense and long-lasting auroral activity (observable through the AE index). However, these phenomena were not strong enough to produce significant ring current intensification (measured by the middle/low latitude Dst index). In this work we analyze three intervals of strong auroral activity related to interplanetary Alfven waves outside main phases of geomagnetic storms. These events occurred in the years 2002, 2003, and 2005. The ionospheric effects were observed through the vertical Total Electron Content (TEC) data from GPS receivers. Data from three GPS stations were employed in this study: Porto Alegre (POAL, Brazil, Lat. 30.1deg S, Long. 51.1deg W, Dip Lat. 20.7deg S, LT=UT-3 h), Bahia Blanca (VBCA, Argentina, Lat 38.7deg S, Long. 62.3deg W, Dip Lat. 22.4deg S, LT=UT-4 h), and Rio Grande (RIOG, Argentina, Lat. 53.6deg S, Long. 67.8deg W, Dip Lat. 43.6deg S, LT=UT-4 h). For each event three quiet days around the date were used to calculate the VTEC average and standard deviation. These values were assumed as reference for disturbed intervals comparisons. For the three selected intervals we observed VTEC increases in all the analyzed stations. The VTEC values may reach over 50% increases compared to quiet day values. Another remarkable observation is that the POAL station (the most equatorward station) always presents higher increases than the other stations. This effect is reduced as the latitude

  4. Nonlinear astrophysical Alfven waves - Onset and outcome of the modulational instability

    Science.gov (United States)

    Spangler, S. R.

    1985-01-01

    The nonlinear development of Alfven waves is numerically studied, with applications to Alfven waves in astrophysical plasmas. It is found that amplitude-modulated Alfven wave packets undergo a collapse instability in which the wave packets become more intense and of smaller spatial extent. The wave packet steepening is eventually halted in a process most aptly described as soliton formation. A simple analytic model based on the method of characteristics can account for many of the results of the numerical calculations. The instability probably cannot prevent particle pitch angle isotropization due to self-generated Alfven waves. Nonlinear effects of the collapse may modify the process by which energetic electrons are reaccelerated by plasma turbulence. The model calculations can semiquantitatively account for properties of shock-associated Alfven waves in the solar system.

  5. Drift-Kinetic Alfven Waves Observed near a Reconnection X Line in the Earth's Magnetopause

    International Nuclear Information System (INIS)

    We identify drift-kinetic Alfven waves in the vicinity of a reconnection X line on the Earth's magnetopause. The dispersive properties of these waves have been determined using wavelet interferometric techniques applied to multipoint observations from the Cluster spacecraft. Comparison of the observed wave dispersion with that expected for drift-kinetic Alfven waves shows close agreement. The waves propagate outwards from the X line suggesting that reconnection is a kinetic Alfven wave source. Energetic O+ ions observed in these waves indicate that reconnection is a driver of auroral ion outflow

  6. Electrostatic Wave Generation and Transverse Ion Acceleration by Alfvenic Wave Components of BBELF Turbulence

    Science.gov (United States)

    Singh, Nagendra; Khazanov, George; Mukhter, Ali

    2007-01-01

    We present results here from 2.5-D particle-in-cell simulations showing that the electrostatic (ES) components of broadband extremely low frequency (BBELF) waves could possibly be generated by cross-field plasma instabilities driven by the relative drifts between the heavy and light ion species in the electromagnetic (EM) Alfvenic component of the BBELF waves in a multi-ion plasma. The ES components consist of ion cyclotron as well as lower hybrid modes. We also demonstrate that the ES wave generation is directly involved in the transverse acceleration of ions (TAI) as commonly measured with the BBELF wave events. The heating is affected by ion cyclotron resonance in the cyclotron modes and Landau resonance in the lower hybrid waves. In the simulation we drive the plasma by the transverse electric field, E(sub y), of the EM waves; the frequency of E(sub y), omega(sub d), is varied from a frequency below the heavy ion cyclotron frequency, OMEGA(sub h), to below the light ion cyclotron frequency, OMEGA(sub i). We have also performed simulations for E(sub y) having a continuous spectrum given by a power law, namely, |Ey| approx. omega(sub d) (exp -alpha), where the exponent alpha = _, 1, and 2 in three different simulations. The driving electric field generates polarization and ExB drifts of the ions and electrons. When the interspecies relative drifts are sufficiently large, they drive electrostatic waves, which cause perpendicular heating of both light and heavy ions. The transverse ion heating found here is discussed in relation to observations from Cluster, FAST and Freja.

  7. Ion Heating by Fast Particle Induced Alfven Turbulence

    International Nuclear Information System (INIS)

    A novel mechanism that directly transfers energy from Super-Alfvenic energetic ions to thermal ions in high-beta plasmas is described. The mechanism involves the excitation of compressional Alfvin eigenmodes (CAEs) in the frequency range with omega less than or approximately equal to omega(subscript ci). The broadband turbulence resulting from the large number of excited modes causes stochastic diffusion in velocity space, which transfers wave energy to thermal ions. This effect may be important on the National Spherical Torus Experiment (NSTX), and may scale up to reactor scenarios. This has important implications for low aspect ratio reactor concepts, since it potentially allows for the modification of the ignition criterion

  8. Particle simulation of energetic particle driven Alfven modes in NBI heated DIII-D experiments

    International Nuclear Information System (INIS)

    The mutual nonlinear interactions of shear Alfven modes and alpha particles can enhance their transport in burning plasmas. Theoretical and numerical works have shown that rapid transport of energetic ions can take place because of fast growing Alfven modes (e.g. energetic particle driven modes, EPMs). This kind of transport has been observed in experiments as well as in numerical simulations. Hybrid MHD-gyrokinetic codes can investigate linear and nonlinear dynamics of energetic particle (EP) driven modes, retaining the mutual interaction between waves and EPs self-consistently. Self-consistent nonlinear wave-particle interactions (both in configuration and velocity space) are crucial for a correct description of the mode dynamics in the case of strongly driven modes; thus, a non-perturbative approach is mandatory. The knowledge of the threshold characterizing the transition from weakly to strongly driven regimes is of primary importance for burning plasma operations (e.g. for ITER), in order to avoid EPM enhanced EP transport regimes. The hybrid MHD-gyrokinetic code (HMGC) has been applied to the interpretation of phenomena observed in present experiments with neutral beam (NB) heating. In reversed-shear beam-heated DIII-D discharges, a large discrepancy between the expected and measured EP radial density profiles has been observed in the presence of large Alfvenic activity. HMGC simulations with EP radial profiles expected from classical NB deposition as input give rise to strong EPM activity, resulting in relaxed EP radial profiles at saturation level close to experimental measurements. The frequency spectra obtained from several simulations with different toroidal mode numbers, as calculated during the saturated phase when the strong EPMs transform in weak reversed-shear Alfven modes, are quite close to experimental observations both in absolute frequency and in radial localization. In this work, we discuss in particular the effects of nonlinear coupling

  9. Relationship Between Alfvenic Fluctuations and Heavy Ion Heating in the Cusp at 1 Re

    Science.gov (United States)

    Coffey, Victoria; Chandler, Michael; Singh, Nagendra

    2008-01-01

    We look at the effect of heavy ion heating from their coupling with observed broadband (BB-ELF) emissions. These wave fluctuations are common to many regions of the ionosphere and magnetosphere and have been described as spatial turbulence of dispersive Alfven waves (DAW) with short perpendicular wavelengths. With Polar passing through the cusp at 1 Re in the Spring of 1996, we show the correlation of their wave power with mass-resolved O+ derived heating rates. This relationship lead to the study of the coupling of the thermal O+ ions and these bursty electric fields. We demonstrate the role of these measurements in the suggestion of DAW and stochastic ion heating and the observed density cavity characteristics.

  10. Plasma heating inside ICMEs by Alfvenic fluctuations dissipation

    CERN Document Server

    Li, Hui; He, Jiansen; Zhang, Lingqian; Richardson, John D; Belcher, John W; Tu, Cui

    2016-01-01

    Nonlinear cascade of low-frequency Alfvenic fluctuations (AFs) is regarded as one candidate of the energy sources to heat plasma during the non-adiabatic expansion of interplanetary coronal mass ejections (ICMEs). However, AFs inside ICMEs were seldom reported in the literature. In this study, we investigate AFs inside ICMEs using observations from Voyager 2 between 1 and 6 au. It is found that AFs with high degree of Alfvenicity frequently occurred inside ICMEs, for almost all the identified ICMEs (30 out of 33 ICMEs), and 12.6% of ICME time interval. As ICMEs expand and move outward, the percentage of AF duration decays linearly in general. The occurrence rate of AFs inside ICMEs is much less than that in ambient solar wind, especially within 4 au. AFs inside ICMEs are more frequently presented in the center and at the boundaries of ICMEs. In addition, the proton temperature inside ICME has a similar distribution. These findings suggest significant contribution of AFs on local plasma heating inside ICMEs.

  11. Exact Analytical Solution of Alfven Waves in Nonuniform Plasmas

    International Nuclear Information System (INIS)

    Full text: The propagation of Alfven waves in non-uniform plasmas is described through linear second-order differential equations, governing the total pressure and radial plasma velocity. In general, these two differential equations only admit numerical solutions, whose behavior is very much complicated especially near resonance surfaces which encompass essential degeneracies. It is well-known that most existing analytical methods, including the famous Wentzel-Karmers-Brillouin (WKB) approximation fail near such singularities. In this paper, a power analytical method, which is recently developed and named the Differential Transfer Matrix Method (DTMM), is applied to find a rigorously exact solution to the problem of interest. We also present an approximate solution based on the Airy functions. (author)

  12. The Structure of Plasma Heating in Gyrokinetic Alfv\\'enic Turbulence

    CERN Document Server

    Navarro, A B; Told, D; Groselj, D; Crandall, P; Jenko, F

    2016-01-01

    We analyze plasma heating in weakly collisional kinetic Alfv\\'en wave (KAW) turbulence using high resolution gyrokinetic simulations spanning the range of scales between the ion and the electron gyroradii. Real space structures that have a higher than average heating rate are shown not to be confined to current sheets. This novel result is at odds with previous studies, which use the electromagnetic work in the local electron fluid frame, i.e. $\\mathbf{J} \\!\\cdot\\! (\\mathbf{E} + \\mathbf{v}_e\\times\\mathbf{B})$, as a proxy for turbulent dissipation to argue that heating follows the intermittent spatial structure of the electric current. Furthermore, we show that electrons are dominated by parallel heating while the ions prefer the perpendicular heating route. We comment on the implications of the results presented here.

  13. Modulational instability and envelope-solitons for nonlinear Alfven waves propagating along the magnetic field in plasmas

    International Nuclear Information System (INIS)

    The modulational instability and envelope-solitons are analyzed for the Alfven waves propagating along the static magnetic field in cold collisionless plasmas, using the modified nonlinear Schroedinger equation previously derived by the authors. The modulational instability occurs in the left-hand circularly polarized Alfven wave (left Alfven wave) for a small amplitude but does not for an amplitude larger than the critical value. On the other hand, the instability never occurs in the right-hand circularly polarized Alfven wave (right Alfven wave). When the modulational instability does not occur, the rarefactive and compressive envelope-solitons exist in the left Alfven wave and the two types of the rarefactive envelope-solitons exist in the right Alfven wave. (auth.)

  14. Reversed shear Alfven eigenmode stabilization by localized electron cyclotron heating

    Energy Technology Data Exchange (ETDEWEB)

    Van Zeeland, M A; Hyatt, A W; Lohr, J; Petty, C C [General Atomics, PO Box 85608 San Diego, CA 92186-5608 (United States); Heidbrink, W W [University of California-Irvine, Irvine, CA 92697 (United States); Nazikian, R; Solomon, W M; Gorelenkov, N N; Kramer, G J [Princeton Plasma Physics Laboratory, Princeton, NJ 08543-0451 (United States); Austin, M E [University of Texas-Austin, Austin, TX 78712 (United States); Berk, H L [Institute for Fusion Studies, University of Texas at Austin, Austin, TX 78712 (United States); Holcomb, C T; Makowski, M A [Lawrence Livermore National Laboratory, Livermore, CA (United States); McKee, G R [University of Wisconsin-Madison, Madison, WI 53726 (United States); Sharapov, S E [Euratom/UKAEA Fusion Association, Culham, Abingdon, Oxfordshire, OX14 3DB (United Kingdom); Rhodes, T L [University of California-Los Angeles, Los Angeles, California, 90095 (United States)], E-mail: vanzeeland@fusion.gat.com

    2008-03-15

    Reversed shear Alfven eigenmode (RSAE) activity in DIII-D is stabilized by electron cyclotron heating (ECH) applied near the minimum of the magnetic safety factor (q{sub min}) in neutral beam heated discharges with reversed-magnetic shear. The degree of RSAE stabilization, fast ion density and the volume averaged neutron production (S{sub n}) are highly dependent on ECH deposition location relative to q{sub min}. While discharges with ECH stabilization of RSAEs have higher S{sub n} and more peaked fast ion profiles than discharges with significant RSAE activity, neutron production remains strongly reduced (up to 60% relative to TRANSP predictions assuming classical fast ion transport) even when RSAEs are stabilized.

  15. Multiple-gap theory of toroidal Alfven waves with kinetic effects

    International Nuclear Information System (INIS)

    The stability of kinetic toroidal Alfven waves with multi-gap coupling is analyzed by using the two-dimensional ballooning transform. An alternate convergence scheme, based on the smallness of the inverse aspect ratio, is devised. The resulting wave functions are oscillatory and do not balloon in contrast to the wave functions of conventional ballooning theory. It is shown that the single-gap theory is a special, weak shear (s → 0) limit of the formalism. Analytical and numerical results for the two fundamental branches, the ideal toroidal Alfven eigenmode (TAE), and the kinetic toroidal Alfven eigenmode (KTAE) are presented and discussed

  16. Energy dissipation of Alfven wave packets deformed by irregular magnetic fields in solar-coronal arches

    Science.gov (United States)

    Similon, Philippe L.; Sudan, R. N.

    1989-01-01

    The importance of field line geometry for shear Alfven wave dissipation in coronal arches is demonstrated. An eikonal formulation makes it possible to account for the complicated magnetic geometry typical in coronal loops. An interpretation of Alfven wave resonance is given in terms of gradient steepening, and dissipation efficiencies are studied for two configurations: the well-known slab model with a straight magnetic field, and a new model with stochastic field lines. It is shown that a large fraction of the Alfven wave energy flux can be effectively dissipated in the corona.

  17. Alfven Waves in a Plasma Sheet Boundary Layer Associated with Near-Tail Magnetic Reconnection

    Institute of Scientific and Technical Information of China (English)

    YUAN Zhi-Gang; DENG Xiao-Hua; PANG Ye; LI Shi-You; WANG Jing-Fang

    2007-01-01

    We report observations from Geotail satellite showing that large Poynting fluxes associated with Alfven waves in the plasma sheet boundary layer(PSBL) occur in the vicinity of the near-tail reconnection region on 10 December 1996.During the period of large Poynting fluxex,Geotail also observed strong tailward plasma flws.These observations demonstrate the importance of near-tail reconnection process as the energy source of Alfven waves in the PSBL.Strong tailward(Earthward)plasma flows ought to be an important candidate in generating Alfven waves.Furthermore,the strong pertutbations not only of the magnetic field but also of the electric field observed in the PSBL indicate that the PSBL plays an important role in the generation and propagation of the energy flux associated with Alfven waves.

  18. Formation of convective cells by modulational instability of drift Alfven waves

    International Nuclear Information System (INIS)

    A model equation describing drift Alfven wave with E X B nonlinearity is derived. For a special ordering a nonlinear Schroedinger equation is derived, which governs modulational instability of the drift Alfven wave. Translational invariance is assumed along the magnetic field. The relation between the characteristic scale lengths parallel and perpendicular to the drift flow for the onset of cell formation has been found. The influence of perpendicular ion viscosity is also discussed. (Auth.)

  19. Observation of an Alfv\\'en Wave Parametric Instability in a Laboratory Plasma

    CERN Document Server

    Dorfman, S

    2016-01-01

    A shear Alfv\\'en wave parametric instability is observed for the first time in the laboratory. When a single finite $\\omega/\\Omega_i$ kinetic Alfv\\'en wave (KAW) is launched in the Large Plasma Device above a threshold amplitude, three daughter modes are produced. These daughter modes have frequencies and parallel wave numbers that are consistent with copropagating KAW sidebands and a low frequency nonresonant mode. The observed process is parametric in nature, with the frequency of the daughter modes varying as a function of pump wave amplitude. The daughter modes are spatially localized on a gradient of the pump wave magnetic field amplitude in the plane perpendicular to the background field, suggesting that perpendicular nonlinear forces (and therefore $k_{\\perp}$ of the pump wave) play an important role in the instability process. Despite this, modulational instability theory with $k_{\\perp}=0$ has several features in common with the observed nonresonant mode and Alfv\\'en wave sidebands.

  20. Alfven-wave particle interaction in finite-dimensional self-consistent field model

    International Nuclear Information System (INIS)

    A low-dimensional Hamiltonian model is derived for the acceleration of ions in finite amplitude Alfven waves in a finite pressure plasma sheet. The reduced low-dimensional wave-particle Hamiltonian is useful for describing the reaction of the accelerated ions on the wave amplitudes and phases through the self-consistent fields within the envelope approximation. As an example, the authors show for a single Alfven wave in the central plasma sheet of the Earth's geotail, modeled by the linear pinch geometry called the Harris sheet, the time variation of the wave amplitude during the acceleration of fast protons

  1. Kinetic effects on Alfven wave nonlinearity. II. The modified nonlinear wave equation

    International Nuclear Information System (INIS)

    The study of kinetic effects on Alfven wave nonlinearity is continued. Previously obtained expressions for the perturbed (by an Alfven wave) ion and electron distribution functions are used to obtain a nonlinear wave equation for parallel-propagating, circularly polarized waves. The results are cast in the form of a modified version of the familiar derivative nonlinear Schroedinger equation. The approach in obtaining this equation is a hybrid one; fluid theory is used to the greatest extent possible, and kinetic theory is introduced where the correction is believed to be most important. Fluid theory at two levels of sophistication is employed. The first uses a simple scalar pressure term. This approach yields physical insight and illuminates the field-aligned fluid flow and the associated plasma density perturbation as a major contributor to Alfven wave nonlinearity. The second approach employs a tensor pressure term that in general will be necessary. The results indicate that kinetic effects in general produce a nonlinear wave equation that is of a different functional form than the derivative nonlinear Schroedinger equation, as previously reported by Mjolhus and Wyller [Phys. Scr. 33, 442 (1986); J. Plasma Phys. 40, 229 (1988)]. The coefficient of the derivative cubic term depends on the plasma beta in a way which, in general, is quite different from the fluid expression. In addition, a functionally novel term appears in the modified equation. The magnitude of this term, named the ''nonlocal term'' by Mjolhus and Wyller, can be large when the plasma beta is comparable to unity. The susceptibility of the modified equation to modulational instability is studied. Kinetic effects cause modulational instability of wave packets, even when fluid theory would predict modulational stability. This modulational instability occurs for both right- and left-hand polarized waves

  2. AMPTE/CCE observations of substorm-associated standing Alfven waves in the midnight sector

    Science.gov (United States)

    Takahashi, K.; Mcentire, R. W.; Potemra, T. A.; Kokubun, S.; Sakurai, T.

    1988-01-01

    Magnetic-field and medium-energy particle data from the AMPTE/CCE spacecraft are used to study substorm-associated ULF pulsations in the midnight sector at a radial distance of 8 to 9 earth radii. The particle data are used to identify ion injections and to detect the electric field of ULF waves. A case study of the events on May 23, 1985 shows that the waves have the properties of a fundamental-mode standing Alfven wave. It is suggested that these observations are evidence of substorm-associated standing Alfven waves in the nightside magnetosphere.

  3. Long-Alfven-wave trains in collisionless plasmas. I. Kinetic theory

    International Nuclear Information System (INIS)

    A generalized kinetic derivative nonlinear Schroedinger equation for the multidimensional dynamics of Alfven wave trains propagating along an ambient magnetic field is derived from the Vlasov-Maxwell equations by a reductive perturbative expansion. It retains in addition to the Landau damping, the coupling to longitudinally averaged fields driven by both transverse gradients and kinetic effects. These mean fields that modulate the propagation speed of the wave play a main role in transverse instabilities of extended Alfven wave packets and in the filamentation phenomenon. This long-wave model also provides a benchmark for Landau-fluid descriptions of collisionless plasmas

  4. Kinetic Alfven wave in the presence of kappa distribution function in plasma sheet boundary layer

    International Nuclear Information System (INIS)

    The particle aspect approach is adopted to investigate the trajectories of charged particles in the electromagnetic field of kinetic Alfven wave. Expressions are found for the dispersion relation, damping/growth rate and associated currents in the presence of kappa distribution function. Kinetic effect of electrons and ions are included to study kinetic Alfven wave because both are important in the transition region. It is found that the ratio β of electron thermal energy density to magnetic field energy density and the ratio of ion to electron thermal temperature (Ti/Te), and kappa distribution function affect the dispersion relation, damping/growth rate and associated currents in both cases(warm and cold electron limit).The treatment of kinetic Alfven wave instability is based on assumption that the plasma consist of resonant and non resonant particles. The resonant particles participate in an energy exchange process, whereas the non resonant particles support the oscillatory motion of the wave

  5. Destabilization of hydromagnetic drift-Alfven waves in a finite pressure, collisional plasma

    International Nuclear Information System (INIS)

    The hydromagnetic drift mode of the coupled drift-Alfven wave is destabilized as a standing wave in a dense, current-free plasma in the presence of a density gradient. When an axial electron current is drawn, a localized Alfven mode propagating against the current is destabilized, in addition to the unstable drift mode now propagating along the current. The measured wave properties, dispersion, and dependence on plasma parameters are found to agree with the theory derived for a finite β, collisional plasma

  6. Threaded-Field-Lines Model for the Low Solar Corona Powered by the Alfven Wave Turbulence

    CERN Document Server

    Sokolov, Igor V; Manchester, Ward B; Ozturk, Doga Can Su; Szente, Judit; Taktakishvili, Aleksandre; Tóth, Gabor; Jin, Meng; Gombosi, Tamas I

    2016-01-01

    We present an updated global model of the solar corona, including the transition region. We simulate the realistic tree-dimensional (3D) magnetic field using the data from the photospheric magnetic field measurements and assume the magnetohydrodynamic (MHD) Alfv\\'en wave turbulence and its non-linear dissipation to be the only source for heating the coronal plasma and driving the solar wind. In closed field regions the dissipation efficiency in a balanced turbulence is enhanced. In the coronal holes we account for a reflection of the outward propagating waves, which is accompanied by generation of weaker counter-propagating waves. The non-linear cascade rate degrades in strongly imbalanced turbulence, thus resulting in colder coronal holes. The distinctive feature of the presented model is the description of the low corona as almost-steady-state low-beta plasma motion and heat flux transfer along the magnetic field lines. We trace the magnetic field lines through each grid point of the lower boundary of the g...

  7. Excitation of global Alfven Eigenmodes by RF heating in JET

    Energy Technology Data Exchange (ETDEWEB)

    Kerner, W.; Borba, D.; Gormezano, C.; Huysmans, G.; Porcelli, F.; Start, D. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Fasoli, A. [Ecole Polytechnique Federale, Lausanne (Switzerland). Centre de Recherche en Physique des Plasma (CRPP); Sharapov, S. [Kurchatov Institute, Moscow (Russian Federation)

    1994-07-01

    The alpha-particle confinement of future D-T experiments at JET can be severely degraded by Global Alfven Eigenmodes (AE). Scenarios for the excitation of Alfven Eigenmodes in usual (e.g. D-D) plasmas are proposed, which provide a MHD diagnostic and allow the study of the transport of super-Alfvenic ions. Active studies with separate control of TAE amplitude and energetic particle destabilization, measuring the plasma response, give more information than passive studies, in particular concerning the damping mechanisms. The TAE excitation can be achieved by means of the saddle coil and the ICRH antenna. The experimental method is introduced together with a theoretical model for RF excitation. (authors). 6 refs., 3 figs.

  8. Excitation of global Alfven Eigenmodes by RF heating in JET

    International Nuclear Information System (INIS)

    The alpha-particle confinement of future D-T experiments at JET can be severely degraded by Global Alfven Eigenmodes (AE). Scenarios for the excitation of Alfven Eigenmodes in usual (e.g. D-D) plasmas are proposed, which provide a MHD diagnostic and allow the study of the transport of super-Alfvenic ions. Active studies with separate control of TAE amplitude and energetic particle destabilization, measuring the plasma response, give more information than passive studies, in particular concerning the damping mechanisms. The TAE excitation can be achieved by means of the saddle coil and the ICRH antenna. The experimental method is introduced together with a theoretical model for RF excitation. (authors). 6 refs., 3 figs

  9. Quantum Treatment of Kinetic Alfv\\'en Waves instability in a dusty plasma: Magnetized ions

    CERN Document Server

    Rubab, N

    2016-01-01

    The dispersion relation of kinetic Alfv\\'en wave in inertial regime is studied in a three component non-degenerate streaming plasma. A lin- ear dispersion relation using fluid- Vlasov equation for quantum plasma is also derived. The quantum correction CQ raised due to the insertion of Bohm potential in Vlasov model causes the suppression in the Alfven wave frequency and the growth rates of instability. A number of analytical expressions are derived for various modes of propagation. It is also found that many system parameters, i.e, streaming velocity, dust charge, num- ber density and quantum correction significantly influence the dispersion relation and the growth rate of instability.

  10. Alfven Wave Collisions, The Fundamental Building Block of Plasma Turbulence II: Numerical Solution

    CERN Document Server

    Nielson, Kevin D; Dorland, William

    2013-01-01

    This paper presents the numerical verification of an asymptotic analytical solution for the nonlinear interaction between counterpropagating Alfven waves, the fundamental building block of astrophysical plasma turbulence. The analytical solution, derived in the weak turbulence limit using the equations of incompressible MHD, is compared to a nonlinear gyrokinetic simulation of an Alfven wave collision. The agreement between these methods signifies that the incompressible solution satisfactorily describes the essential dynamics of the nonlinear energy transfer, even under the weakly collisional plasma conditions relevant to many astrophysical environments.

  11. The soliton transform and a possible application to nonlinear Alfven waves in space

    Science.gov (United States)

    Hada, T.; Hamilton, R. L.; Kennel, C. F.

    1993-01-01

    The inverse scattering transform (IST) based on the derivative nonlinear Schroedinger (DNLS) equation is applied to a complex time series of nonlinear Alfven wave data generated by numerical simulation. The IST describes the long-time evolution of quasi-parallel Alfven waves more efficiently than the Fourier transform, which is adapted to linear rather than nonlinear problems. When dissipation is added, so the conditions for the validity of the DNLS are not strictly satisfied, the IST continues to provide a compact description of the wavefield in terms of a small number of decaying envelope solitons.

  12. Magnetohydrodynamics in the Early Universe and the Damping of Non-linear Alfven Waves

    CERN Document Server

    Subramanian, K; Subramanian, Kandaswamy; Barrow, John D.

    1998-01-01

    The evolution and viscous damping of cosmic magnetic fields in the early universe, is analysed. Using the fact that the fluid, electromagnetic, and shear viscous energy-momentum tensors are all conformally invariant, the evolution is transformed from the expanding universe setting into that in flat spacetime. Particular attention is paid to the evolution of nonlinear Alfven modes. For a small enough magnetic field, which satisfies our observational constraints, these wave modes either oscillate negligibly or, when they do oscillate, become overdamped. Hence they do not suffer Silk damping on galactic and subgalactic scales. The smallest scale which survives damping depends on the field strength and is of order a dimensionless Alfven velocity times the usual baryon-photon Silk damping scale. After recombination, nonlinear effects can convert the Alfven mode into compressional, gravitationally unstable waves and seed cosmic structures if the cosmic magnetic field is sufficiently strong.

  13. Energetic particle destabilization of shear Alfven waves in stellarators and tokamaks

    International Nuclear Information System (INIS)

    An important issue for ignited devices is the resonant destabilization of shear Alfven waves by energetic populations. These instabilities have been observed in a variety of toroidal plasma experiments in recent years, including: beam-destabilized toroidal Alfven instabilities (TAE) in low magnetic field tokamaks, ICRF destabilized TAE's in higher field tokamaks, and global Alfven instabilities (GAE) in low shear stellarators. In addition, excitation and study of these modes is a significant goal of the TFIR-DT program and a component of the ITER physics tasks. The authors have developed a gyrofluid model which includes the wave-particle resonances necessary to excite such instabilities. The TAE linear mode structure is calculated nonperturbatively, including many of the relevant damping mechanisms, such as: continuum damping, non-ideal effects (ion FLR and electron collisionality), and ion/electron Landau damping. This model has been applied to both linear and nonlinear regimes for a range of experimental cases using measured profiles

  14. Reflection and dissipation of Alfv\\'en waves in interstellar clouds

    OpenAIRE

    Pinto, C.; A. Verdini; Galli, D.; Velli, M.

    2012-01-01

    Context: Supersonic nonthermal motions in molecular clouds are often interpreted as long-lived magnetohydrodynamic (MHD) waves. The propagation and amplitude of these waves is affected by local physical characteristics, most importantly the gas density and the ionization fraction. Aims: We study the propagation, reflection and dissipation of Alfv\\'en waves in molecular clouds deriving the behavior of observable quantities such as the amplitudes of velocity fluctuations and the rate of energy ...

  15. Kinetic structures of shear Alfven and acoustic wave spectra in burning plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Zonca, F; Biancalani, A; Chavdarovski, I; Chen, L; Di Troia, C; Wang, X, E-mail: fulvio.zonca@enea.it

    2010-11-01

    We present a general theoretical framework for discussing the physics of low frequency fluctuation spectra of shear Alfven and acoustic waves in toroidal plasmas of fusion interest. This framework helps identifying the relevant dynamics and, thus, interpreting experimental observations. We also discuss the roles of such general theoretical framework for verification and validation of numerical simulation codes vs. analytic predictions and experimental results.

  16. Kinetic structures of shear Alfven and acoustic wave spectra in burning plasmas

    International Nuclear Information System (INIS)

    We present a general theoretical framework for discussing the physics of low frequency fluctuation spectra of shear Alfven and acoustic waves in toroidal plasmas of fusion interest. This framework helps identifying the relevant dynamics and, thus, interpreting experimental observations. We also discuss the roles of such general theoretical framework for verification and validation of numerical simulation codes vs. analytic predictions and experimental results.

  17. Reflection and dissipation of Alfv\\'en waves in interstellar clouds

    CERN Document Server

    Pinto, C; Galli, D; Velli, M

    2012-01-01

    Context: Supersonic nonthermal motions in molecular clouds are often interpreted as long-lived magnetohydrodynamic (MHD) waves. The propagation and amplitude of these waves is affected by local physical characteristics, most importantly the gas density and the ionization fraction. Aims: We study the propagation, reflection and dissipation of Alfv\\'en waves in molecular clouds deriving the behavior of observable quantities such as the amplitudes of velocity fluctuations and the rate of energy dissipation. Methods: We formulated the problem in terms of Els\\"asser variables for transverse MHD waves propagating in a one-dimensional inhomogeneous medium, including the dissipation due to collisions between ions and neutrals and to a nonlinear turbulent cascade treated in a phenomenological way. We considered both steady-state and time-dependent situations and solved the equations of the problem numerically with an iterative method and a Lax-Wendroff scheme, respectively. Results: Alfv\\'en waves incident on overdens...

  18. Effects of ion-neutral collisions on Alfven waves: The presence of forbidden zone and heavy damping zone

    Energy Technology Data Exchange (ETDEWEB)

    Weng, C. J. [Department of Physics, National Cheng Kung University, Tainan 701, Taiwan (China); Institute of Space Science, National Central University, Jhongli 320, Taiwan (China); Lee, L. C. [Institute of Space Science, National Central University, Jhongli 320, Taiwan (China); Institute of Earth Science, Academia Sinica, Nankang 115, Taiwan (China); Kuo, C. L. [Institute of Space Science, National Central University, Jhongli 320, Taiwan (China); Wang, C. B. [CAS Key Laboratory of Geospace Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei (China)

    2013-03-15

    Alfven waves are low-frequency transverse waves propagating in a magnetized plasma. We define the Alfven frequency {omega}{sub 0} as {omega}{sub 0}=kV{sub A}cos{theta}, where k is the wave number, V{sub A} is the Alfven speed, and {theta} is the angle between the wave vector and the ambient magnetic field. There are partially ionized plasmas in laboratory, space, and astrophysical plasma systems, such as in the solar chromosphere, interstellar clouds, and the earth ionosphere. The presence of neutral particles may modify the wave frequency and cause damping of Alfven waves. The effects on Alfven waves depend on two parameters: (1) {alpha}=n{sub n}/n{sub i}, the ratio of neutral density (n{sub n}), and ion density (n{sub i}); (2) {beta}={nu}{sub ni}/{omega}{sub 0}, the ratio of neutral collisional frequency by ions {nu}{sub ni} to the Alfven frequency {omega}{sub 0}. Most of the previous studies examined only the limiting case with a relatively large neutral collisional frequency or {beta} Much-Greater-Than 1. In the present paper, the dispersion relation for Alfven waves is solved for all values of {alpha} and {beta}. Approximate solutions in the limit {beta} Much-Greater-Than 1 as well as {beta} Much-Less-Than 1 are obtained. It is found for the first time that there is a 'forbidden zone (FZ)' in the {alpha}-{beta} parameter space, where the real frequency of Alfven waves becomes zero. We also solve the wavenumber k from the dispersion equation for a fixed frequency and find the existence of a 'heavy damping zone (HDZ).' We then examine the presence of FZ and HDZ for Alfven waves in the ionosphere and in the solar chromosphere.

  19. Observational Quantification of the Energy Dissipated by Alfv\\'en Waves in a Polar Coronal Hole: Evidence that Waves Drive the Fast Solar Wind

    CERN Document Server

    Hahn, Michael

    2013-01-01

    We present a measurement of the energy carried and dissipated by Alfv\\'en waves in a polar coronal hole. Alfv\\'en waves have been proposed as the energy source that heats the corona and drives the solar wind. Previous work has shown that line widths decrease with height in coronal holes, which is a signature of wave damping, but have been unable to quantify the energy lost by the waves. This is because line widths depend on both the non-thermal velocity v_nt and the ion temperature T_i. We have implemented a means to separate the T_i and v_nt contributions using the observation that at low heights the waves are undamped and the ion temperatures do not change with height. This enables us to determine the amount of energy carried by the waves at low heights, which is proportional to v_nt. We find the initial energy flux density present was 6.7 +/- 0.7 x 10^5 erg cm^-2 s^-1, which is sufficient to heat the coronal hole and acccelerate the solar wind during the 2007 - 2009 solar minimum. Additionally, we find tha...

  20. Turbulence in the sub-Alfv\\'enic solar wind driven by reflection of low-frequency Alfv\\'en waves

    CERN Document Server

    Verdini, A; Buchlin, E

    2009-01-01

    We study the formation and evolution of a turbulent spectrum of Alfv\\'en waves driven by reflection off the solar wind density gradients, starting from the coronal base up to 17 solar radii, well beyond the Alfv\\'enic critical point. The background solar wind is assigned and 2D shell models are used to describe nonlinear interactions. We find that the turbulent spectra are influenced by the nature of reflected waves. Close to the base, these give rise to a flatter and steeper spectrum for the outgoing and reflected waves respectively. At higher heliocentric distance both spectra evolve toward an asymptotic Kolmogorov spectrum. The turbulent dissipation is found to account for at least half of the heating required to sustain the background imposed solar wind and its shape is found to be determined by the reflection-determined turbulent heating below 1.5 solar radii. Therefore reflection and reflection-driven turbulence are shown to play a key role in the accelerationof the fast solar wind and origin of the tur...

  1. Experimental evidence of Alfv\\'en wave propagation in a Gallium alloy

    CERN Document Server

    Alboussiere, Thierry; Debray, François; La Rizza, Patrick; Masson, Jean-Paul; Plunian, Franck; Ribeiro, Adolfo; Schmitt, Denys

    2011-01-01

    Experiments with a liquid metal alloy, galinstan, are reported and show clear evidence of Alfv\\'en wave propagation as well as resonance of Alfv\\'en modes. Galinstan is liquid at room temperature, and although its electrical conductivity is not as large as that of liquid sodium or NaK, it has still been possible to study Alfv\\'en waves, thanks to the use of intense magnetic fi elds, up to 13 teslas. The maximal values of Lundquist number, around 60, are similar to that of the reference experimental study by Jameson [1]. The generation mechanism for Alfv\\'en waves and their refl ection is studied carefully. Numerical simulations have been performed and have been able to reproduce the experimental results despite the fact that the simulated magnetic Prandtl number was much larger than that of galinstan. An originality of the present study is that a poloidal disturbance (magnetic and velocity fields) is generated, allowing us to track its propagation from outside the conducting domain, hence without interfering.

  2. Alfven wave coupled with flow-driven fluid instability in interpenetrating plasmas

    CERN Document Server

    Vranjes, J

    2015-01-01

    The Alfven wave is analyzed in case of one quasineutral plasma propagating with some constant speed $v_0$ through another static quasineutral plasma. A dispersion equation is derived describing the Alfven wave coupled with the flow driven mode $\\omega= k v_0$ and solutions are discussed analytically and numerically. The usual solutions for two oppositely propagating Alfv\\'en waves are substantially modified due to the flowing plasma. More profound is modification of the solution propagating in the negative direction with respect to the magnetic field and the plasma flow. For a large enough flow speed (exceeding the Alfven speed in the static plasma), this negative solution may become non-propagating, with frequency equal to zero. In this case it represents a spatial variation of the electromagnetic field. For greater flow speed it becomes a forward mode, and it may merge with the positive one. This merging of the two modes represents the starting point for a flow-driven instability, with two complex-conjugate...

  3. Stability of global Alfven waves (TAE, EAE) in JET tritium discharges

    International Nuclear Information System (INIS)

    The study of MHD modes driven unstable by energetic particles due to additional heating and, in particular, by alpha particles is crucial for the prediction of α-confinement for future JET D-T discharges aiming at QDT≅1. In this paper we analyse the toroidicity and elongation induced Alfven eigenmodes (TAE, EAE), their damping and their destabilisation by energetic particles. The spectral code CASTOR (Complex Alfven Spectrum for Toroidal Plasmas) together with the equilibrium solver HELENA provides the tool for the analysis of the ideal and dissipative MHD spectrum. (author) 3 refs., 3 figs

  4. Nonlinear coupling of O- and X-mode radio emission and Alfven waves in the solar corona

    International Nuclear Information System (INIS)

    The nonlinear coupling of extraordinary and ordinary waves via kinetic Alfven waves (KAWs) is investigated on the basis of two fluid magnetohydrodynamics. The equation governing the time dependence of electric field of excited O-mode is found. We estimate the time of effective coupling between modes and corresponding interaction distance in solar corona. Our theoretical results show that the X- and O-mode couplings via Alfven waves can be efficient depolarization mechanism for the coronal radioemission

  5. Magnetosphere--Ionosphere Coupling: Effects of Plasma Alfven Wave Relative Motion

    Science.gov (United States)

    Christiansen, P. J.; Dum, C. T.

    1989-06-01

    The introduction of relative perpendicular motion between a flux-tube supporting shear Alfven wave activity and the background plasma is studied in the context of the coupling of a wave generating region with a distant ionosphere. The results of a representative simulation, using an extended version of the code developed by Lysak & Dum (J. geophys. Res. 88, 365 (1983)), are used as a basis for interpreting some aspects of recent satellite observations.

  6. Propagation of Alfv\\'enic Waves From Corona to Chromosphere and Consequences for Solar Flares

    OpenAIRE

    Russell, A. J. B.; Fletcher, L.

    2013-01-01

    How do magnetohydrodynamic waves travel from the fully ionized corona, into and through the underlying partially ionized chromosphere, and what are the consequences for solar flares? To address these questions, we have developed a 2-fluid model (of plasma and neutrals) and used it to perform 1D simulations of Alfv\\'en waves in a solar atmosphere with realistic density and temperature structure. Studies of a range of solar features (faculae, plage, penumbra and umbra) show that energy transmis...

  7. Transverse dynamics of dispersive Alfven waves. II. Driving of a reduced magnetohydrodynamic flow

    International Nuclear Information System (INIS)

    The nonlinear dynamics resulting from transverse and quasi-transverse instabilities of a finite-amplitude dispersive Alfven wave propagating along an ambient magnetic field is studied by direct numerical simulations of the three-dimensional Hall-magnetohydrodynamic (Hall-MHD) equations. When the pump wave has a moderate amplitude and a long enough wavelength, one observes the generation of nonlinear structures in the form of helical filaments for the transverse magnetic field intensity and the density fluctuations. An interesting feature is the development of a quasi-incompressible turbulent flow, with a longitudinal characteristic scale large compared to the Alfven wavelength, that remains spectrally well separated from the wave throughout the evolution. The coexistence of this 'reduced MHD' flow with nonlinear Alfven waves was predicted on the basis of an asymptotic analysis [A. Gazol, T. Passot, and P. L. Sulem, Phys. Plasmas 6, 3114 (1999)] carried out in the long-wavelength limit. Whereas in this regime the generation of the reduced MHD flow is negligible, it becomes significant on a time scale of a few wave periods when dispersion is increased. Increasing the dispersion also leads to a faster destabilization of the wave and to a more rapid dissipation, a remarkable effect due to enhanced instability growth rates. In the case of a larger amplitude pump, or of an Alfven wavelength close to the ion-inertial length, the helical structures get fragmented and the spectral gap observed at early times between the large-scale flow and the waves rapidly disappears, leading to a fully three-dimensional MHD turbulent flow

  8. Modification and damping of Alfven waves in a magnetized dusty plasma

    International Nuclear Information System (INIS)

    The dispersion characteristics of the circularly polarized electromagnetic waves along a homogeneous magnetic field in a dusty plasma have been investigated theoretically. The Vlasov equation has been employed to find the response of the magnetized plasma particles where the dust grains form a static background of highly charged and massive centers having certain correlation. It is found that in addition to the usual Landau damping which is negligible in the low temperature approximation, a novel mechanism of damping of the Alfven waves due to the dust comes into play. The modification and damping of the Alfven waves depend on the dust perturbation parameters, unequal densities of plasma particles, the average correlation length of the dust grains, temperature of the plasma and the magnetic field. (author)

  9. Supergranulation-driven Alfven waves in the solar chromosphere and related phenomena.

    Science.gov (United States)

    Hollweg, J. V.

    1972-01-01

    It has recently been recognized that Alfven waves frequently dominate the microstructure of the solar wind at the orbit of the earth. We seek a solar source for these waves, and consider here their excitation by the supergranular motions. The wave equation is solved in a horizontally stratified, bi-exponential solar atmosphere. The interaction of Alfven wave motions associated with adjacent supergranules is discussed qualitatively. The Alfven wave effectively conveys the supergranular motions to great heights in the chromosphere. These motions are oppositely directed above intersupergranule boundaries, and compress the magnetic field there. A naive calculation of the compression, based on balancing dynamic and magnetic pressures, leads to adequate agreement with observations of the chromospheric network. We find that the magnetic field is appreciably compressed only below about 1500 km, and on this basis we reject theories of spicule formation which require large vertical magnetic fields at the heights reached by spicules. We advance a theory for spicule formation, in which spicules form as a result of matter being squeezed upward, out of the compression region between adjacent supergranules.

  10. Flow shear suppression of turbulence using externally driven ion Bernstein and Alfven waves

    International Nuclear Information System (INIS)

    The utilization of externally-launched radio-frequency waves as a means of active confinement control through the generation of sheared poloidal flows is explored. For low-frequency waves, kinetic Alfven waves are proposed, and are shown to drive sheared E x B flows as a result of the radial variation in the electromagnetic Reynolds stress. In the high frequency regime, ion Bernstein waves are considered, and shown to generate sheared poloidal rotation through the ponderomotive force. In either case, it is shown that modest amounts of absorbed power (∼ few 100 kW) are required to suppress turbulence in a region of several cm radial width. 9 refs

  11. On the reflection of Alfv\\'en waves and its implication for Earth's core modeling

    CERN Document Server

    Schaeffer, Nathanaël; Cardin, Philippe; Marie, Drouard

    2011-01-01

    Alfv\\'en waves propagate in electrically conducting fluids in the presence of a magnetic field. Their reflection properties depend on the ratio between the kinematic viscosity and the magnetic diffusivity of the fluid, also known as the magnetic Prandtl number Pm. In the special case Pm=1, there is no reflection on an insulating, no-slip boundary, and the wave energy is entirely dissipated in the boundary layer. We investigate the consequences of this remarkable behaviour for the numerical modeling of torsional Alfv\\'en waves (also known as torsional oscillations), which represent a special class of Alfv\\'en waves, in rapidly rotating spherical shells. They consist of geostrophic motions and are thought to exist in the fluid cores of planets with internal magnetic field. In the geophysical limit Pm 0.3, which is the range of values for which geodynamo numerical models operate. As a result, geodynamo models with no-slip boundary conditions cannot exhibit torsional oscillation normal modes.

  12. Kinetic Alfv\\'en waves generation by large-scale phase-mixing

    CERN Document Server

    Vasconez, C L; Valentini, F; Servidio, S; Matthaeus, W H; Malara, F

    2015-01-01

    One view of the solar-wind turbulence is that the observed highly anisotropic fluctuations at spatial scales near the proton inertial length $d_p$ may be considered as Kinetic Alfv\\'en waves (KAWs). In the present paper, we show how phase-mixing of large-scale parallel propagating Alfv\\'en waves is an efficient mechanism for the production of KAWs at wavelengths close to $d_p$ and at large propagation angle with respect to the magnetic field. Magnetohydrodynamic (MHD), Hall-Magnetohydrodynamic (HMHD), and hybrid Vlasov-Maxwell (HVM) simulations modeling the propagation of Alfv\\'en waves in inhomogeneous plasmas are performed. In linear regime, the role of dispersive effects is singled out by comparing MHD and HMHD results. Fluctuations produced by phase-mixing are identified as KAWs through a comparison of polarization of magnetic fluctuations and wave group velocity with analytical linear predictions. In the nonlinear regime, comparison of HMHD and HVM simulations allows to point out the role of kinetic effe...

  13. Torsional Alfven Waves in Solar Magnetic Flux Tubes of Axial Symmetry

    CERN Document Server

    Murawski, K; Musielak, Z E; Srivastava, A K; Kraskiewicz, J

    2015-01-01

    Aims: Propagation and energy transfer of torsional Alfv\\'en waves in solar magnetic flux tubes of axial symmetry is studied. Methods: An analytical model of a solar magnetic flux tube of axial symmetry is developed by specifying a magnetic flux and deriving general analytical formulae for the equilibrium mass density and a gas pressure. The main advantage of this model is that it can be easily adopted to any axisymmetric magnetic structure. The model is used to simulate numerically the propagation of nonlinear Alfv\\'en waves in such 2D flux tubes of axial symmetry embedded in the solar atmosphere. The waves are excited by a localized pulse in the azimuthal component of velocity and launched at the top of the solar photosphere, and they propagate through the solar chromosphere, transition region, and into the solar corona. Results: The results of our numerical simulations reveal a complex scenario of twisted magnetic field lines and flows associated with torsional Alfv\\'en waves as well as energy transfer to t...

  14. Energy densities of Alfven waves between 0.7 and 1.6 AU. [in interplanetary medium

    Science.gov (United States)

    Belcher, J. W.; Burchsted, R.

    1974-01-01

    Plasma and field data from Mariner 4 and 5 between 0.7 and 1.6 AU are used to study the radial dependence of the levels of microscale fluctuation associated with interplanetary Alfven waves. The observed decrease of these levels with increasing distance from the sun is consistent with little or no local generation or damping of the ambient Alfven waves over this range of radial distance.

  15. Inbound waves in the solar corona: a direct indicator of Alfv\\'en Surface location

    CERN Document Server

    DeForest, C E; McComas, D J

    2014-01-01

    The tenuous supersonic solar wind that streams from the top of the corona passes through a natural boundary -- the Alfv\\'en surface -- that marks the causal disconnection of individual packets of plasma and magnetic flux from the Sun itself. The Alfv\\'en surface is the locus where the radial motion of the accelerating solar wind passes the radial Alfv\\'en speed, and therefore any displacement of material cannot carry information back down into the corona. It is thus the natural outer boundary of the solar corona, and the inner boundary of interplanetary space. Using a new and unique motion analysis to separate inbound and outbound motions in synoptic visible-light image sequences from the COR2 coronagraph on board the STEREO-A spacecraft, we have identified inbound wave motion in the outer corona beyond 6 solar radii for the first time, and used it to determine that the Alfv\\'en surface is at least 12.5 solar radii from the Sun over the polar coronal holes and 17 solar radii in the streamer belt, well beyond ...

  16. Experimental investigations of driven Alfven wave resonances in a tokamak plasma using carbon dioxide laser interferometry

    International Nuclear Information System (INIS)

    The first direct observation of the internal structure of driven global Alfven eigenmodes in a tokamak plasma is presented. A carbon dioxide laser scattering/interferometer has been designed, built, and installed on the PRETEXT tokamak. By using this diagnostic system in the interferometer configuration, we have for the first time, thoroughly investigated the resonance conditions required for, and the spatial wave field structure of, driven plasma eigenmodes at frequencies below the ion cyclotron frequency in a confined, high temperature, tokamak plasma

  17. Magnetohydrodynamics in the Early Universe and the Damping of Non-linear Alfven Waves

    OpenAIRE

    Subramanian, Kandaswamy; Barrow, John D.

    1997-01-01

    The evolution and viscous damping of cosmic magnetic fields in the early universe, is analysed. Using the fact that the fluid, electromagnetic, and shear viscous energy-momentum tensors are all conformally invariant, the evolution is transformed from the expanding universe setting into that in flat spacetime. Particular attention is paid to the evolution of nonlinear Alfven modes. For a small enough magnetic field, which satisfies our observational constraints, these wave modes either oscilla...

  18. Plasma acceleration by the interaction of parallel propagating Alfv\\'en waves

    OpenAIRE

    Mottez, Fabrice

    2014-01-01

    It is shown that two circularly polarised Alfv\\'en waves that propagate along the ambient magnetic field in an uniform plasma trigger non oscillating electromagnetic field components when they cross each other. The non-oscilliating field components can accelerate ions and electrons with great efficiency. This work is based on particle-in-cell (PIC) numerical simulations and on analytical non-linear computations. The analytical computations are done for two counter-propagating monochromatic wa...

  19. Effect of Rossby and Alfv\\'{e}n waves on the dynamics of the tachocline

    OpenAIRE

    Leprovost, Nicolas; Kim, Eun-Jin

    2006-01-01

    To understand magnetic diffusion, momentum transport, and mixing in the interior of the sun, we consider an idealized model of the tachocline, namely magnetohydrodynamics (MHD) turbulence on a $\\beta$ plane subject to a large scale shear (provided by the latitudinal differential rotation). This model enables us to self-consistently derive the influence of shear, Rossby and Alfv\\'{e}n waves on the transport properties of turbulence. In the strong magnetic field regime, we find that the turbule...

  20. Spectroscopic Observations and Modelling of Impulsive Alfv\\'en Waves Along a Polar Coronal Jet

    CERN Document Server

    Jelínek, P; Murawski, K; Kayshap, P; Dwivedi, B N

    2015-01-01

    Using the Hinode/EIS 2$"$ spectroscopic observations, we study the intensity, velocity, and FWHM variations of the strongest Fe XII 195.12 \\AA\\ line along the jet to find the signature of Alfv\\'en waves. We simulate numerically the impulsively generated Alfv\\'en waves within the vertical Harris current-sheet, forming the jet plasma flows, and mimicking their observational signatures. Using the FLASH code and the atmospheric model with embedded weakly expanding magnetic field configuration within a vertical Harris current-sheet, we solve the two and half-dimensional (2.5-D) ideal magnetohydrodynamic (MHD) equations to study the evolution of Alfv\\'en waves and vertical flows forming the plasma jet. At a height of $\\sim 5~\\mathrm{Mm}$ from the base of the jet, the red-shifted velocity component of Fe XII 195.12 \\AA\\ line attains its maximum ($5~\\mathrm{km\\,s}^{-1}$) which converts into a blue-shifted one between the altitude of $5-10~\\mathrm{Mm}$. The spectral intensity continously increases up to $10~\\mathrm{Mm...

  1. The effect of plasma shear flow on drift Alfven instabilities of a finite beta plasma and on anomalous heating of ions by ion cyclotron turbulence

    Science.gov (United States)

    Jo, Young Hyun; Lee, Hae June; Mikhailenko, Vladimir V.; Mikhailenko, Vladimir S.

    2016-01-01

    It was derived that the drift-Alfven instabilities with the shear flow parallel to the magnetic field have significant difference from the drift-Alfven instabilities of a shearless plasma when the ion temperature is comparable with electron temperature for a finite plasma beta. The velocity shear not only modifies the frequency and the growth rate of the known drift-Alfven instability, which develops due to the inverse electron Landau damping, but also triggers a combined effect of the velocity shear and the inverse ion Landau damping, which manifests the development of the ion kinetic shear-flow-driven drift-Alfven instability. The excited unstable waves have the phase velocities along the magnetic field comparable with the ion thermal velocity, and the growth rate is comparable with the frequency. The development of this instability may be the efficient mechanism of the ion energization in shear flows. The levels of the drift--Alfven turbulence, resulted from the development of both instabilities, are determined from the renormalized nonlinear dispersion equation, which accounts for the nonlinear effect of the scattering of ions by the electromagnetic turbulence. The renormalized quasilinear equation for the ion distribution function, which accounts for the same effect of the scattering of ions by electromagnetic turbulence, is derived and employed for the analysis of the ion viscosity and ions heating, resulted from the interactions of ions with drift-Alfven turbulence. In the same way, the phenomena of the ion cyclotron turbulence and anomalous anisotropic heating of ions by ion cyclotron plasma turbulence has numerous practical applications in physics of the near-Earth space plasmas. Using the methodology of the shearing modes, the kinetic theory of the ion cyclotron turbulence of the plasma with transverse current with strong velocity shear has been developed.

  2. Observation of fast-ion Doppler-shifted cyclotron resonance with shear Alfven waves

    International Nuclear Information System (INIS)

    The Doppler-shifted cyclotron resonance (ω-kzvz=Ωf) between fast ions and shear Alfven waves is experimentally investigated (ω, wave frequency; kz, axial wavenumber; vz, fast-ion axial speed; Ωf, fast-ion cyclotron frequency). A test particle beam of fast ions is launched by a Li+ source in the helium plasma of the LArge Plasma Device (LAPD) [W. Gekelman, H. Pfister, Z. Lucky, J. Bamber, D. Leneman, and J. Maggs, Rev. Sci. Instrum. 62, 2875 (1991)], with shear Alfven waves (SAW) (amplitude δ B/B up to 1%) launched by a loop antenna. A collimated fast-ion energy analyzer measures the nonclassical spreading of the beam, which is proportional to the resonance with the wave. A resonance spectrum is observed by launching SAWs at 0.3-0.8ωci. Both the magnitude and frequency dependence of the beam-spreading are in agreement with the theoretical prediction using a Monte Carlo Lorentz code that launches fast ions with an initial spread in real/velocity space and random phases relative to the wave. Measured wave magnetic field data are used in the simulation.

  3. Stimulated emission of fast Alfv\\'en waves within magnetically confined fusion plasmas

    CERN Document Server

    Cook, J W S; Chapman, S C

    2016-01-01

    A fast Alfv\\'en wave with finite amplitude is shown to grow by a stimulated emission process that we propose for exploitation in toroidal magnetically confined fusion plasmas. Stimulated emission occurs while the wave propagates inward through the outer mid-plane plasma, where a population inversion of the energy distribution of fusion-born ions is observed to arise naturally. Fully nonlinear first principles simulations, which self-consistently evolve particles and fields under the Maxwell-Lorentz system, demonstrate this novel "alpha-particle channelling" scenario for the first time.

  4. The combined toroidicity, ellipticity and triangularity effects on the energy deposition of Alfven modes in pre-heated, low aspect ratio tokamaks

    International Nuclear Information System (INIS)

    The combined plasma non-uniformity effects on the energy deposition of Alfven waves launched by an external antenna in pre-heated spherical tokamaks are investigated. The following relevant physical processes are here possible: (a) the emergence of gaps in the shear Alfven continuum spectrum and the generation of discrete global Alfven eigenmodes with frequencies inside the gaps; (b) multi-wave interactions, interactions of gaps of the same kind (e.g., toroidicity induced) and of different kinds (toroidicity, ellipticity and triangularity induced) as well as of secondary order gaps arising when a pair of modes is coupled to one or more modes through other coupling parameters; (c) basic wave-plasma interactions as propagation, reflection, mode-conversion, tunneling and deposition. Thus, we solved numerically the full 2D wave equations for the vector and scalar potentials, using a quite general two-fluid resistive tensor-operator, without any geometrical limitations. The results obtained indicate the existence of antenna-launched wave characteristics for which the power is most efficiently coupled in outer regions of plasmas, which is of special interest for low aspect ratio tokamaks, e.g., for the generation of non-inductive current drive as well as for turbulence suppression and transport barriers formation

  5. Alfvenic tornadoes

    CERN Document Server

    Shukla, P K

    2012-01-01

    It is shown that a three-dimensional (3D) modified-kinetic Alfv\\'en waves (m-KAWs) can propagate in the form of Alfv\\'enic tornadoes characterized by plasma density whirls or magnetic flux ropes carrying orbital angular momentum (OAM). By using the two fluid model, together with Amp\\`ere's law, we derive the wave equation for a 3D m-KAWs in a magnetoplasma with $m_e/m_i \\ll \\beta \\ll 1$, where $m_e$ $(m_i)$ is the electron (ion) mass, $\\beta =4 \\pi n_0 k_B (T_e + T_i)/B_0^2$, $n_0$ the unperturbed plasma number density, $k_B$ the Boltzmann constant, $T_e (T_e)$ the electron (ion) temperature, and $B_0$ the strength of the ambient magnetic field. The 3D m-KAW equation admits solutions in the form of a Laguerre-Gauss (LG) Alfv\\'enic vortex beam or Alfv\\'enic tornadoes with plasma density whirls that support the dynamics of Alfv\\'en magnetic flux ropes.

  6. Alfven waves and current relaxation: attenuation at high frequencies and large resistivity

    International Nuclear Information System (INIS)

    The dispersion relations of Alfven waves propagating in a resistive plasma are explored by assuming a finite relaxation time for the current density. It is shown that the proposed approach is consistent with the hydromagnetic approximation. An extension for the equation governing the space and time evolution of Alfven waves is provided. New results are found at high values of the wave frequency ω: for a small resistivity, the wavelength increases as the cube of the equilibrium magnetic field but decreases with the cube of ω; for a large resistivity, the wave attenuation does not depend on ω, saturating to a finite value which is fully determined by the relaxation time of the current density. A transition frequency, ωt, between two sharply distinct regimes of the perturbation is identified: for ω t, the disturbance propagates in the resistive plasma as an attenuated oscillation; for ω > ωt the wave ceases very rapidly to oscillate (in space), its amplitude saturating to a finite value. The results presented here may be relevant for investigations of some transient phenomena in plasma physics such as the reconnection of magnetic field lines.

  7. Non-inductive electric current generation with the Alfven waves

    International Nuclear Information System (INIS)

    Non-inductive current generation by means of radio frequency waves is studied using one-dimensional (1D) quasilinear equations. The main results obtained in this thesis are the general expressions for the current generated, for the efficiency of current generation and for the critical power - the lowest power required for current saturation. (M.W.O.)

  8. Plasma acceleration by the interaction of parallel propagating Alfv\\'en waves

    CERN Document Server

    Mottez, Fabrice

    2014-01-01

    It is shown that two circularly polarised Alfv\\'en waves that propagate along the ambient magnetic field in an uniform plasma trigger non oscillating electromagnetic field components when they cross each other. The non-oscilliating field components can accelerate ions and electrons with great efficiency. This work is based on particle-in-cell (PIC) numerical simulations and on analytical non-linear computations. The analytical computations are done for two counter-propagating monochromatic waves. The simulations are done with monochromatic waves and with wave packets. The simulations show parallel electromagnetic fields consistent with the theory, and they show that the particle acceleration result in plasma cavities and, if the waves amplitudes are high enough, in ion beams. These acceleration processes could be relevant in space plasmas. For instance, they could be at work in the auroral zone and in the radiation belts of the Earth magnetosphere. In particular, they may explain the origin of the deep plasma...

  9. Effects of heavy ion temperature on low-frequency kinetic Alfven waves

    International Nuclear Information System (INIS)

    Heavy ion-electron (or proton) temperature ratio varies in a wide range in the solar and space environment. In this paper, proton and heavy ion temperatures are included in a three-fluid plasma model. For the specified parameters, low-frequency (<< heavy ion gyrofrequency) kinetic Alfven waves (KAWs) with sub- and super-Alfvenic speeds are found to coexist in the same plasma environment. Our results show that the temperature ratio of heavy ions to electrons can considerably affect the dispersion, propagation, and electromagnetic polarizations of the KAWs. In particular, the temperature ratio can increase the ratio of parallel to perpendicular electric fields and the normalized electric to magnetic field ratio, the variations of which are greatly different in regions with a high heavy ion temperature and with a low one. The results may help to understand the physical mechanism of some energization processes of heavy ions in the solar and space plasma environment. Effects of the ratio of electron thermal to Alfven speeds and the heavy ion abundance on these parameters are also discussed.

  10. Kinetic Alfv\\'{e}n solitary and rogue waves in superthermal plasmas

    CERN Document Server

    Bains, A; Xia, L -D

    2014-01-01

    We investigate the small but finite amplitude solitary Kinetic Alfv\\'{e}n waves (KAWs) in low $\\beta$ plasmas with superthermal electrons modeled by a kappa-type distribution. A nonlinear Korteweg-de Vries (KdV) equation describing the evolution of KAWs is derived by using the standard reductive perturbation method. Examining the dependence of the nonlinear and dispersion coefficients of the KdV equation on the superthermal parameter $\\kappa$, plasma $\\beta$ and obliqueness of propagation, we show that these parameters may change substantially the shape and size of solitary KAW pulses. Only sub-Alfv\\'enic, compressive solitons are supported. We then extend the study to examine kinetic Alfv\\'en rogue waves by deriving a nonlinear Schr\\"{o}dinger equation from {the KdV} equation. Rational solutions that form rogue wave envelopes are obtained. We examine how the behavior of rogue waves depends on the plasma parameters in question, finding that the rogue envelopes are lowered with increasing electron superthermal...

  11. Transverse dynamics of dispersive Alfven waves. I. Direct numerical evidence of filamentation

    International Nuclear Information System (INIS)

    The three-dimensional dynamics of a small-amplitude monochromatic Alfven wave propagating along an ambient magnetic field is simulated by direct numerical integration of the Hall-magnetohydrodynamics equations. As predicted by the two-dimensional nonlinear Schroedinger equation or by more general amplitude equations retaining the coupling to low-frequency magnetosonic waves, the transverse instability of the pump leads to wave collapse and formation of intense magnetic filaments, in spite of the presence of competing, possibly linearly dominant, instabilities that in some instances distort the above structures. In computational boxes, including a large number of pump wavelengths, an early arrest of the collapse is possible under the effect of quasi-transverse instabilities that drive magnetosonic waves and also prescribe the directions of the filaments

  12. Preliminary experimental study of the antenna module for Alfven wave excitation system in TCABR Tokamak

    International Nuclear Information System (INIS)

    The results of the initial experimental studies of the Alfven wave antenna module, which is destined to be a part of the advanced antenna system of TCABR tokamak, are presented. The tests were carried out in a specially constructed vacuum chamber and included the measurement of antenna electrical parameters and testing of the power diagnostic tools. The complex impedances and inductive mutual coupling of antenna loops were measured and results were compared with theoretical calculations. The tests have shown that the parameters of the antenna module have values according to the design. (author)

  13. Nonlinear reflection process of linearly-polarized, broadband Alfv\\'en waves in the fast solar wind

    CERN Document Server

    Shoda, Munehito

    2016-01-01

    Using one-dimensional numerical simulations, we study the elementary process of Alfv\\'{e}n wave reflection in a uniform medium, including nonlinear effects. In the linear regime, Alfv\\'{e}n wave reflection is triggered only by the inhomogeneity of the medium, whereas in the nonlinear regime, it can occur via nonlinear wave-wave interactions. Such nonlinear reflection (backscattering) is typified by decay instability. In most studies of decay instabilities, the initial condition has been a circularly polarized Alfv\\'{e}n wave. In this study we consider a linearly polarized Alfv\\'en wave, which drives density fluctuations by its magnetic pressure force. For generality, we also assume a broadband wave with a red-noise spectrum. In the data analysis, we decompose the fluctuations into characteristic variables using local eigenvectors, thus revealing the behaviors of the individual modes. Different from circular-polarization case, we find that the wave steepening produces a new energy channel from the parent Alfv\\...

  14. Damping of Alfven waves by Turbulence and its Consequences: from Cosmic-Rays Streaming to Launching Winds

    CERN Document Server

    Lazarian, A

    2016-01-01

    This paper considers turbulent damping of Alfven waves in magnetized plasmas. We identify two cases of damping, one related to damping of cosmic rays streaming instability, the other related to damping of Alfven waves emitted by a macroscopic wave source, e.g. stellar atmosphere. The physical difference between the two cases is that in the former case the generated waves are emitted in respect to the local direction of magnetic field, in the latter in respect to the mean field. The scaling of damping is different in the two cases. We the regimes of turbulence ranging from subAlfvenic to superAlfvenic we obtain analytical expressions for the damping rates and define the ranges of applicability of these expressions. Describing the damping of the streaming instability, we find that for subAlfvenic turbulence the range of cosmic ray energies influenced by weak turbulence is unproportionally large compared to the range of scales that the weak turbulence is present. On the contrary, the range of cosmic ray energies...

  15. Filamentation of dispersive Alfven waves in density channels: Hall magnetohydrodynamics description

    International Nuclear Information System (INIS)

    Filamentation of dispersive Alfven waves initiated by low or high density channels (depending on the plasma beta) is simulated numerically in the framework of ideal Hall magnetohydrodynamics, and asymptotically modeled with a two-dimensional nonlinear Schroedinger equation including a linear attracting potential. Compared with the dynamics in a homogeneous plasma, the phenomenon is accelerated and occurs for a broader range of parameters. In the case of an isolated channel with a width comparable to the pump wavelength, the transverse wave collapse can be replaced by a moderate amplification. In many cases, a relatively complex dynamics takes place, characterized by an oscillation between magnetic filaments and magnetic ribbons, leading to the formation of small scales at which dissipative effects could become relevant. Alfven vortices, governed by the equations of the reduced magnetohydrodynamics, are also identified in the simulations, in spite of their small amplitude relative to the wave. The formation of structures under the effect of periodic or random distributions of low and high density channels is also discussed

  16. Integrated campaign to study the stationary inertial Alfven wave in the laboratory and space regimes

    International Nuclear Information System (INIS)

    A small, off-axis mesh-anode electrode at one plasma-column end is used to create a paraxial channel of electron current and depleted density in the large plasma device upgrade at UCLA. We show that the on-axis, larger, surrounding-plasma column rotates about its cylindrical axis because a radial electric field is imposed by a multiple-segmented-disc termination electrode on the same end as the mesh-anode electrode. The radial profile of azimuthal velocity is shown to be consistent with predictions of rigid-body rotation. Launched inertial Alfven waves are shown to concentrate in the off-axis channel of electron current and depleted plasma density. In the absence of launched waves, time varying boundary conditions, or spatially structured boundary conditions, a non-fluctuating, non-traveling pattern in the plasma density is shown to arise spontaneously in the channel, but only in the combined presence of electron current, density depletion, and spontaneously in the channel, cross-field convection (i.e. rotation). These results may be relevant to the stationary Alfven wave in the inertial regime in space and laboratory plasmas

  17. Studies of the Jet in BL Lacertae. II. Superluminal Alfv\\'en Waves

    CERN Document Server

    Cohen, M H; Arshakian, T G; Clausen-Brown, E; Homan, D C; Hovatta, T; Kovalev, Y Y; Lister, M L; Pushkarev, A B; Richards, J L; Savolainen, T

    2014-01-01

    Ridge lines on the pc-scale jet of the active galactic nucleus BL Lac display transverse patterns that move superluminally downstream. The patterns are not ballistic, but are analogous to waves on a whip. Their apparent speeds $\\beta_\\mathrm{app}$ (units of $c$) range from 4.2 to 13.5, corresponding to $\\beta_\\mathrm{wave}^\\mathrm{gal}= 0.981 - 0.998$ in the galaxy frame. We show that the magnetic field in the jet is well-ordered with a strong transverse component, and assume that it is helical and that the transverse patterns are longitudinal Alfv\\'en waves. The wave-induced transverse speed of the jet is non-relativistic ($\\beta_\\mathrm{tr}^\\mathrm{gal}\\sim 0.09$) and in agreement with our assumption of low-amplitude waves. In 2010 the wave activity subsided and the jet displayed a mild wiggle that had a complex oscillatory behavior. The waves are excited by changes in the position angle of the recollimation shock, in analogy to exciting a wave on a whip by shaking it. Simple models of the system are presen...

  18. [Heat waves: health impacts].

    Science.gov (United States)

    Marto, Natália

    2005-01-01

    During the summer of 2003, record high temperatures were reported across Europe, causing thousands of casualties. Heat waves are sporadic recurrent events, characterised by intense and prolonged heat, associated with excess mortality and morbidity. The most frequent cause of death directly attributable to heat is heat stroke but heat waves are known to cause increases in all-cause mortality, specially circulatory and respiratory mortality. Epidemiological studies demonstrate excess casualties cluster in specific risk groups. The elderly, those with chronic medical conditions and the socially isolated are particularly vulnerable. Air conditioning is the strongest protective factor against heat-related disorders. Heat waves cause disease indirectly, by aggravating chronic disorders, and directly, by causing heat-related illnesses (HRI). Classic HRI include skin eruptions, heat cramps, heat syncope, heat exhaustion and heat stroke. Heat stroke is a medical emergency characterised by hyperthermia and central nervous system dysfunction. Treatment includes immediate cooling and support of organ-system function. Despite aggressive treatment, heat stroke is often fatal and permanent neurological damage is frequent in those who survive. Heat related illness and death are preventable through behavioural adaptations, such as use of air conditioning and increased fluid intake. Other adaptation measures include heat emergency warning systems and intervention plans and environmental heat stress reduction. Heat related mortality is expected to rise as a consequence of the increasing proportion of elderly persons, the growing urban population, and the anticipated increase in number and intensity of heat waves associated with global warming. Improvements in surveillance and response capability may limit the adverse health conditions of future heat waves. It is crucial that health professionals are prepared to recognise, prevent and treat HRI and learn to cooperate with local health

  19. Kinetic Alfven solitary waves in a magnetized plasma with superthermal electrons

    Energy Technology Data Exchange (ETDEWEB)

    Panwar, A., E-mail: anurajrajput@gmail.com, E-mail: ryu201@postech.ac.kr, E-mail: bainsphysics@yahoo.co.in; Ryu, C. M., E-mail: anurajrajput@gmail.com, E-mail: ryu201@postech.ac.kr, E-mail: bainsphysics@yahoo.co.in [POSTECH, Hyoja-Dong San 31, KyungBuk, Pohang 790-784 (Korea, Republic of); Bains, A. S., E-mail: anurajrajput@gmail.com, E-mail: ryu201@postech.ac.kr, E-mail: bainsphysics@yahoo.co.in [Department of Physics and Engineering Physics, University of Saskatchewan, Saskatchewan S7N5E2 (Canada)

    2015-09-15

    A study of the ion Larmor radius effects on the solitary kinetic Alfven waves (SKAWs) in a magnetized plasma with superthermal electrons is presented by employing the kinetic theory. The linear dispersion relation of SKAW is shown to depend on the superthermal parameter κ, ion to electron temperature ratio, and the angle of wave propagation. Using the Sagdeev potential approach, the energy balance equation has been derived to study the dynamics of SKAWs. The effects of various plasma parameters are investigated for the propagation of SKAWs. It is shown that only compressive solitons can exist and in the Maxwellian limit our results are in good agreement with previous studies. Further, the characteristics of small amplitude SKAWs are investigated. Present study could be useful for the understanding of SKAWs in a low β plasma in astrophysical environment, where particle distributions are superthermal in nature.

  20. Kinetic Alfven solitary waves in a magnetized plasma with superthermal electrons

    International Nuclear Information System (INIS)

    A study of the ion Larmor radius effects on the solitary kinetic Alfven waves (SKAWs) in a magnetized plasma with superthermal electrons is presented by employing the kinetic theory. The linear dispersion relation of SKAW is shown to depend on the superthermal parameter κ, ion to electron temperature ratio, and the angle of wave propagation. Using the Sagdeev potential approach, the energy balance equation has been derived to study the dynamics of SKAWs. The effects of various plasma parameters are investigated for the propagation of SKAWs. It is shown that only compressive solitons can exist and in the Maxwellian limit our results are in good agreement with previous studies. Further, the characteristics of small amplitude SKAWs are investigated. Present study could be useful for the understanding of SKAWs in a low β plasma in astrophysical environment, where particle distributions are superthermal in nature

  1. Doppler-shifted cyclotron resonance of fast ions with circularly polarized shear Alfven waves

    International Nuclear Information System (INIS)

    The Doppler-shifted cyclotron resonance between fast ions and shear Alfven waves (SAWs) has been experimentally investigated with a test-particle fast-ion (Li+) beam launched in the helium plasma of the Large Plasma Device [Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)]. Left- or right-hand circularly polarized SAWs are launched by an antenna with four current channels. A collimated fast-ion energy analyzer characterizes the resonance by measuring the nonclassical spreading of the averaged beam signal. Left-hand circularly polarized SAWs resonate with the fast ions but right-hand circularly polarized SAWs do not. The measured fast-ion profiles are compared with simulations by a Monte Carlo Lorentz code that uses the measured wave field data.

  2. Wave and plasma heating

    International Nuclear Information System (INIS)

    In the field of wave heating absorption studies of plasma magnetic waves in the theta pinch are extended to axially inhomogeneous waves. In the Plasmaus 4 experiment direct plasma production has been accomplished for overcritical densities and high magnetic fields. The numerical methods developed at IPF for plasma simulation studies have been applied successfully to further problems. (orig./GG)

  3. Alfvenic tornadoes

    OpenAIRE

    Shukla, P. K.

    2012-01-01

    It is shown that a three-dimensional (3D) modified-kinetic Alfv\\'en waves (m-KAWs) can propagate in the form of Alfv\\'enic tornadoes characterized by plasma density whirls or magnetic flux ropes carrying orbital angular momentum (OAM). By using the two fluid model, together with Amp\\`ere's law, we derive the wave equation for a 3D m-KAWs in a magnetoplasma with $m_e/m_i \\ll \\beta \\ll 1$, where $m_e$ $(m_i)$ is the electron (ion) mass, $\\beta =4 \\pi n_0 k_B (T_e + T_i)/B_0^2$, $n_0$ the unpert...

  4. Final report for DOE-FG02-02ER54688: Study of nonlinear interactions between counterpropagating shear Alfven waves

    Energy Technology Data Exchange (ETDEWEB)

    Carter, T A

    2006-11-16

    Final report for DOE Plasma Physics Junior Faculty Development award DOE-FG02-02ER54688. Reports on research undertaken from 8/1/2002 until 5/15/2006, investigating nonlinear interactions between Alfven waves in a laboratory experiment.

  5. A search for evidence of the evolution of rotational discontinuities in the solar wind from nonlinear Alfven waves

    Science.gov (United States)

    Neugebauer, M.; Buti, B.

    1990-01-01

    Results are presented of a study designed to confirm the suspected relation between Alfven solitons (steepened Afven waves) and rotational discontinuities (RDs) in the solar wind. The ISEE 3 data were used to search for the predicted correlations between the beta value of plasma, the sense of polarization of the discontinuity, and changes of the magnetic field strength and plasma density across the discontinuity. No statistically significant evidence was found for the evolution of RDs from Alfven solitons. A possibility is suggested that the observations made could have been far from the regions in which the RDs were formed.

  6. Solitary Kinetic Alfven Waves in a Low-β Dusty Plasma

    Institute of Scientific and Technical Information of China (English)

    CHEN Yin-Hua; LU Wei

    2000-01-01

    The nonlinear kinetic Alfven waves in a low-β(0<β<1)dusty plasma have been investigated with the fluid model of three-component plasma. The nonlinear equation governing the perturbation density of electrons in a form of the energy integral has been derived. In the approximation of small amplitude, the soliton solution for the perturbation density of electrons is found, and the characteristics of solitons in different range of plasma parameters is studied numerically. The results show that the density dip or hump can be formed in a dusty plasma for different ranges of parameters, the amplitude of density dip is enhanced and the amplitude of density hump is reduced with increasing dust grain content.

  7. Damping of Alfven waves in solar partially ionized plasmas: effect of neutral helium in multi-fluid approach

    OpenAIRE

    Zaqarashvili, T. V.; Khodachenko, M. L.; Rucker, H.O.

    2011-01-01

    Chromospheric and prominence plasmas contain neutral atoms, which may change the plasma dynamics through collision with ions. Most of the atoms are neutral hydrogen, but a significant amount of neutral helium may also be present in the plasma with a particular temperature. Damping of MHD waves due to ion collision with neutral hydrogen is well studied, but the effects of neutral helium are largely unknown. We aim to study the effect of neutral helium in the damping of Alfven waves in solar pa...

  8. The Origin of Ripples in Cool Cores of Galaxy Clusters: Heating by MHD Waves?

    OpenAIRE

    Fujita, Yutaka; Suzuki, Takeru K.; Kudoh, Takahiro; Yokoyama, Takaaki

    2007-01-01

    We consider MHD waves as a heating source of cool cores of galaxy clusters. In particular, we focus on transverse waves (Alfven waves), because they can propagate a longer distance than longitudinal waves (sound waves). Using MHD simulations, we found that the transverse waves can stably heat a cool core if the wave period is large enough (>~ 10^8 yr). Moreover, the longitudinal waves that are created as a by-product of the nonlinear evolution of the transverse waves could be observed as the ...

  9. The Origin of Ripples in Cool Cores of Galaxy Clusters: Heating by MHD Waves?

    CERN Document Server

    Fujita, Y; Kudoh, T; Yokoyama, T; Fujita, Yutaka; Suzuki, Takeru K.; Kudoh, Takahiro; Yokoyama, Takaaki

    2007-01-01

    We consider MHD waves as a heating source of cool cores of galaxy clusters. In particular, we focus on transverse waves (Alfven waves), because they can propagate a longer distance than longitudinal waves (sound waves). Using MHD simulations, we found that the transverse waves can stably heat a cool core if the wave period is large enough (>~ 10^8 yr). Moreover, the longitudinal waves that are created as a by-product of the nonlinear evolution of the transverse waves could be observed as the 'ripples' found in cool cores.

  10. Three dimensional magnetohydrodynamic simulation of linearly polarised Alfven wave dynamics in Arnold-Beltrami-Childress magnetic field

    Science.gov (United States)

    Tsiklauri, David

    2015-04-01

    Previous studies (e.g., Malara et al., Astrophys. J. 533, 523 (2000)) considered small-amplitude Alfven wave (AW) packets in Arnold-Beltrami-Childress (ABC) magnetic field using WKB approximation. They draw a distinction between 2D AW dissipation via phase mixing and 3D AW dissipation via exponentially divergent magnetic field lines. In the former case, AW dissipation time scales as S 1/3 and in the latter as log(S) , where S is the Lundquist number. In this work [1], linearly polarised Alfven wave dynamics in ABC magnetic field via direct 3D magnetohydrodynamic (MHD) numerical simulation is studied for the first time. A Gaussian AW pulse with length-scale much shorter than ABC domain length and a harmonic AW with wavelength equal to ABC domain length are studied for four different resistivities. While it is found that AWs dissipate quickly in the ABC field, contrary to an expectation, it is found the AW perturbation energy increases in time. In the case of the harmonic AW, the perturbation energy growth is transient in time, attaining peaks in both velocity and magnetic perturbation energies within timescales much smaller than the resistive time. In the case of the Gaussian AW pulse, the velocity perturbation energy growth is still transient in time, attaining a peak within few resistive times, while magnetic perturbation energy continues to grow. It is also shown that the total magnetic energy decreases in time and this is governed by the resistive evolution of the background ABC magnetic field rather than AW damping. On contrary, when the background magnetic field is uniform, the total magnetic energy decrease is prescribed by AW damping, because there is no resistive evolution of the background. By considering runs with different amplitudes and by analysing the perturbation spectra, possible dynamo action by AW perturbation-induced peristaltic flow and inverse cascade of magnetic energy have been excluded. Therefore, the perturbation energy growth is attributed

  11. Recent Observations of Plasma and Alfvenic Wave Energy Injection at the Base of the Fast Solar Wind

    CERN Document Server

    McIntosh, Scott W

    2012-01-01

    We take stock of recent observations that identify the episodic plasma heating and injection of Alfvenic energy at the base of fast solar wind (in coronal holes). The plasma heating is associated with the occurrence of chromospheric spicules that leave the lower solar atmosphere at speeds of order 100km/s, the hotter coronal counterpart of the spicule emits radiation characteristic of root heating that rapidly reaches temperatures of the order of 1MK. Furthermore, the same spicules and their coronal counterparts ("Propagating Coronal Disturbances"; PCD) exhibit large amplitude, high speed, Alfvenic (transverse) motion of sufficient energy content to accelerate the material to high speeds. We propose that these (disjointed) heating and accelerating components form a one-two punch to supply, and then accelerate, the fast solar wind. We consider some compositional constraints on this concept, extend the premise to the slow solar wind, and identify future avenues of exploration.

  12. Generation of kinetic Alfven waves in the high-latitude near-Earth magnetotail: A global hybrid simulation

    International Nuclear Information System (INIS)

    In this paper, effects of a fast flow in the tail plasma sheet on the generation of kinetic Alfven waves (KAWs) in the high-latitude of the near-Earth magnetotail are investigated by performing a two-dimensional (2-D) global-scale hybrid simulation, where the plasma flow is initialized by the E×B drift near the equatorial plane due to the existence of the dawn-dusk convection electric field. It is found that firstly, the plasma sheet becomes thinned and the dipolarization of magnetic field appears around (x,z)=(−10.5RE,0.3RE), where RE is the radius of the Earth. Then, shear Alfven waves are excited in the plasma sheet, and the strong earthward flow is braked by the dipole-like magnetic field. These waves propagate along the magnetic field lines toward the polar regions later. Subsequently, KAWs with k⊥≫k∥ are generated in the high-latitude magnetotail due to the existence of the non-uniformity of the magnetic field and density in the polar regions. The ratio of the electric field to the magnetic field in these waves is found to obey the relation (δEz)/(δBy )∼ω/k∥ of KAWs. Our simulation provides a mechanism for the generation of the observed low-frequency shear Alfven waves in the plasma sheet and kinetic Alfven waves in the high-latitude near-Earth magnetotail, whose source is suggested to be the flow braking in the low-latitude plasma sheet

  13. Generation of kinetic Alfven waves in the high-latitude near-Earth magnetotail: A global hybrid simulation

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Zhifang [Key Laboratory of Ionospheric Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029 (China); Beijing National Observatory of Space Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Hong, Minghua; Du, Aimin [Key Laboratory of Ionospheric Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029 (China); Beijing National Observatory of Space Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029 (China); Lin, Yu; Wang, Xueyi [CAS Key Lab of Geoscience Environment, Department of Geophysics and Planetary Science, University of Science and Technology of China, Hefei 230026 (China); Physics Department, Auburn University, 206 Allison Laboratory, Auburn, Alabama 36849-5311 (United States); Wu, Mingyu; Lu, Quanming, E-mail: qmlu@ustc.edu.cn [CAS Key Lab of Geoscience Environment, Department of Geophysics and Planetary Science, University of Science and Technology of China, Hefei 230026 (China); Collaborative Innovation Center of Astronautical Science and Technology (China)

    2015-02-15

    In this paper, effects of a fast flow in the tail plasma sheet on the generation of kinetic Alfven waves (KAWs) in the high-latitude of the near-Earth magnetotail are investigated by performing a two-dimensional (2-D) global-scale hybrid simulation, where the plasma flow is initialized by the E×B drift near the equatorial plane due to the existence of the dawn-dusk convection electric field. It is found that firstly, the plasma sheet becomes thinned and the dipolarization of magnetic field appears around (x,z)=(−10.5R{sub E},0.3R{sub E}), where R{sub E} is the radius of the Earth. Then, shear Alfven waves are excited in the plasma sheet, and the strong earthward flow is braked by the dipole-like magnetic field. These waves propagate along the magnetic field lines toward the polar regions later. Subsequently, KAWs with k{sub ⊥}≫k{sub ∥} are generated in the high-latitude magnetotail due to the existence of the non-uniformity of the magnetic field and density in the polar regions. The ratio of the electric field to the magnetic field in these waves is found to obey the relation (δE{sub z})/(δB{sub y} )∼ω/k{sub ∥} of KAWs. Our simulation provides a mechanism for the generation of the observed low-frequency shear Alfven waves in the plasma sheet and kinetic Alfven waves in the high-latitude near-Earth magnetotail, whose source is suggested to be the flow braking in the low-latitude plasma sheet.

  14. Generation of kinetic Alfven waves in the high-latitude near-Earth magnetotail: A global hybrid simulation

    Science.gov (United States)

    Guo, Zhifang; Hong, Minghua; Lin, Yu; Du, Aimin; Wang, Xueyi; Wu, Mingyu; Lu, Quanming

    2015-02-01

    In this paper, effects of a fast flow in the tail plasma sheet on the generation of kinetic Alfven waves (KAWs) in the high-latitude of the near-Earth magnetotail are investigated by performing a two-dimensional (2-D) global-scale hybrid simulation, where the plasma flow is initialized by the E ×B drift near the equatorial plane due to the existence of the dawn-dusk convection electric field. It is found that firstly, the plasma sheet becomes thinned and the dipolarization of magnetic field appears around (x ,z ) =(-10.5 RE,0.3 RE) , where RE is the radius of the Earth. Then, shear Alfven waves are excited in the plasma sheet, and the strong earthward flow is braked by the dipole-like magnetic field. These waves propagate along the magnetic field lines toward the polar regions later. Subsequently, KAWs with k⊥≫k∥ are generated in the high-latitude magnetotail due to the existence of the non-uniformity of the magnetic field and density in the polar regions. The ratio of the electric field to the magnetic field in these waves is found to obey the relation (δEz)/(δBy )˜ω/k∥ of KAWs. Our simulation provides a mechanism for the generation of the observed low-frequency shear Alfven waves in the plasma sheet and kinetic Alfven waves in the high-latitude near-Earth magnetotail, whose source is suggested to be the flow braking in the low-latitude plasma sheet.

  15. Radiofrequency plasma heating: proceedings

    International Nuclear Information System (INIS)

    The conference proceedings include sessions on Alfven Wave Heating, ICRF Heating and Current Drive, Lower Hybrid Heating and Current Drive, and ECRF Heating. Questions of confinement, diagnostics, instabilities and technology are considered. Individual papers are cataloged separately

  16. James Clerk Maxwell Prize for Plasma Physics Talk: On Nonlinear Physics of Shear Alfv'en Waves

    Science.gov (United States)

    Chen, Liu

    2012-10-01

    Shear Alfv'en Waves (SAW) are electromagnetic oscillations prevalent in laboratory and nature magnetized plasmas. Due to its anisotropic propagation property, it is well known that the linear wave propagation and dispersiveness of SAW are fundamentally affected by plasma nonuniformities and magnetic field geometries; for example, the existence of continuous spectrum, spectral gaps, and discrete eigenmodes in toroidal plasmas. This talk will discuss the crucial roles that nonuniformity and geometry could also play in the physics of nonlinear SAW interactions. More specifically, the focus will be on the Alfv'enic state and its breaking up by finite compressibility, non-ideal kinetic effects, and geometry. In the case of compressibility, finite ion-Larmor-radius effects are shown to qualitatively and quantitatively modify the three-wave parametric decays via the ion-sound perturbations. In the case of geometry, the spontaneous excitation of zonal structures by toroidal Alfv'en eigenmodes is investigated; demonstrating that, for realistic tokamak geometries, zonal current dominates over zonal flow. [4pt] Present address: Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou, China.

  17. Cascade and Dissipation of Solar Wind Turbulence at Electron Scales: Whistlers or Kinetic Alfv\\'en Waves?

    Science.gov (United States)

    Sahraoui, Fouad; Goldstein, Melvyn L.

    2010-01-01

    Over the past few decades, large-scales solar wind (SW) turbulence has been studied extensively, both theoretically and observationally. Observed power spectra of the low frequency turbulence, which can be described in the magnetohydrodynamic (MHD) limit, are shown to obey the Kolmogorov scaling, $k"{ -5/3 }$, down the local proton gyrofrequency ($C{ci} \\sim O.l$-Hz). Turbulence at frequencies above $C{ci}$ has not been thoroughly investigated and remains far less well understood. Above $C{ ci}$ the spectrum steepens to $\\sim f"{ -2.5}$ and a debate exists as to whether the turbulence has become dominated by dispersive kinetic Alfven waves (KA W) or by whistler waves, before it is dissipated at small scales, In a case study Sahraoui et al., PRL (2009) have reported the first direct determination of the dissipation range of solar wind turbulence near the electron gyroscale using the high resolution Cluster magnetic and electric field data (up to $10"2$-Hz in the spacecraft reference frame). Above the Doppler-shifted proton scale $C{\\rho i}$ a new inertial range with a scaling $\\sim f"{ -2.3}$ has been evidenced and shown to remarkably agree with theoretical predictions of a quasi-two-dimensional cascade into KA W turbulence. Here, we use a wider sample of data sets of small scale SW turbulence under different plasma conditions, and investigate under which physical criteria the KA W (or the whistler) turbulence may be observed to carry out the cascade at small scales, These new observations/criteria are compared to the predictions on the cascade and the (kinetic) dissipation from the Vlasov theory. Implications of the results on the heating problem of the solar wind will be discussed.

  18. Scattering of fast magnetoacoustic waves on a ionosphere perturbed by Alfven waves

    International Nuclear Information System (INIS)

    Scattering of fast magnetoacoustic waves on an ionospheric plasma layer is emphasized. The mathematical calculations consider that the magnetoacoustic wave, scattered on the plasma layer with periodical inhomogeneities is the result of some partial wave superposition. The expressions for 0 and +-1 order partial waves and also the corrections to the zeroth order approximation are estimated. The dependence of the amplitude of the +1 order partial waves on the incidence angle THETA and the distance from the boundary of the perturbed plasma layer is studied. With this end in view the analytical form of the amplitudes is expressed. As a rule a periodical dependence of the +1 order partial wave amplitude on THETA and on the distance from the boundary of the pertubed layer occurs. For THETA = 35 deg, it is worth noting a marked maximum for all small perturbations of the +1 order partial wave

  19. Heat Waves Hit Seniors Hardest

    Science.gov (United States)

    ... https://medlineplus.gov/news/fullstory_160425.html Heat Waves Hit Seniors Hardest Risk of high-temperature trouble ... much of the Northeast struggles with a heat wave that isn't expected to ease until the ...

  20. Heat Waves Are Health Threats

    Science.gov (United States)

    ... https://medlineplus.gov/news/fullstory_159694.html Heat Waves Are Health Threats Drink plenty of water and ... 2016 SATURDAY, July 2, 2016 (HealthDay News) -- Heat waves are more than uncomfortable, they can be deadly. ...

  1. Kinetic effects in Alfven and ion-cyclotron-wave propagation: Surface eigenmodes and impurity effects

    International Nuclear Information System (INIS)

    In a circular cylindrical geometry, the author solves a fourth-order set of differential equations numerically for the perturbed fields Eτ and Eperpendicular. The model takes into account the equilibrium current, magnetic shear, finite ω/ωc1 effect, mode conversion effects like finite ion gyroradius and electron inertia, and various dissipative mechanisms such as electron Landau and collisional damping, and minority fundamental and majority second harmonic cyclotron absorption. To illustrate the results, the author plots the perturbed electric fields and the energy absorbed by each species. He first examines cold plasma surface Alfven eigenmodes analytically and numerically in a pure plasma. The motivation for this work is to investigate how to avoid the undesirable edge absorption and introduce the methods for the study of impurity effects. In the two-species plasmas, he considers three special examples: (1) minority oxygen in hydrogen in PRETEXT, (2) minority T or H in deuterium in TFTR. He adopts two models: (i) a radially varying minority charge, or (ii) a radially varying magnetic field to investigate the minority gyroresonance heating. The model (ii) is used to examine these three examples. But the model (i) is only applied to the first one. In model (i), it is found that surface modes can induce the eigenmodes and dissipate substantial energy near the hybrid layer in the interior. Some cases analytically manageable are given an interpretation of why there is large or small energy deposition in this layer. It is shown that this strongly depends on poloidal mode numbers, minority concentrations, and minority charge profiles

  2. Proton Heating in Solar Wind Compressible Turbulence with Collisions between Counter-propagating Waves

    CERN Document Server

    He, Jiansen; Marsch, Eckart; Chen, Christopher H K; Wang, Linghua; Pei, Zhongtian; Zhang, Lei; Salem, Chadi S; Bale, Stuart D

    2015-01-01

    Magnetohydronamic turbulence is believed to play a crucial role in heating the laboratorial, space, and astrophysical plasmas. However, the precise connection between the turbulent fluctuations and the particle kinetics has not yet been established. Here we present clear evidence of plasma turbulence heating based on diagnosed wave features and proton velocity distributions from solar wind measurements by the Wind spacecraft. For the first time, we can report the simultaneous observation of counter-propagating magnetohydrodynamic waves in the solar wind turbulence. Different from the traditional paradigm with counter-propagating Alfv\\'en waves, anti-sunward Alfv\\'en waves (AWs) are encountered by sunward slow magnetosonic waves (SMWs) in this new type of solar wind compressible turbulence. The counter-propagating AWs and SWs correspond respectively to the dominant and sub-dominant populations of the imbalanced Els\\"asser variables. Nonlinear interactions between the AWs and SMWs are inferred from the non-orth...

  3. Alfven solitons in the solar wind

    Science.gov (United States)

    Ovenden, C.; Schwartz, S. J.

    1983-01-01

    A nonlinear Alfven soliton solution of the MHD equations is presented. This solution represents the final state of modulationally unstable Alfven waves. A model of the expected turbulent spectrum due to a collection of such solitons is briefly described.

  4. On the spatial scales of wave heating in the solar chromosphere

    CERN Document Server

    Soler, Roberto; Ballester, Jose Luis

    2015-01-01

    Dissipation of magnetohydrodynamic (MHD) wave energy has been proposed as a viable heating mechanism in the solar chromospheric plasma. Here, we use a simplified one-dimensional model of the chromosphere to theoretically investigate the physical processes and the spatial scales that are required for the efficient dissipation of Alfv\\'en waves and slow magnetoacoustic waves. We consider the governing equations for a partially ionized hydrogen-helium plasma in the single-fluid MHD approximation and include realistic wave damping mechanisms that may operate in the chromosphere, namely Ohmic and ambipolar magnetic diffusion, viscosity, thermal conduction, and radiative losses. We perform an analytic local study in the limit of small amplitudes to approximately derive the lengthscales for critical damping and efficient dissipation of MHD wave energy. We find that the critical dissipation lengthscale for Alfv\\'en waves depends strongly on the magnetic field strength and ranges from 10~m to 1~km for realistic field ...

  5. Finite amplitude solitary Alfven waves in a low-β plasma

    International Nuclear Information System (INIS)

    Different exact forms of Alfven solitons were found recently in low-beta plasmas by different assumptions. The present paper studies the case of parallel ion inertia and current density. Both super and sub-Alfvenian rarefactive solitons were found to exist depending on the angle of inclination of the propagation vector with the magnetic field. (D.Gy.)

  6. An extended hybrid magnetohydrodynamics gyrokinetic model for numerical simulation of shear Alfven waves in burning plasmas

    International Nuclear Information System (INIS)

    Adopting the theoretical framework for the generalized fishbonelike dispersion relation, an extended hybrid magnetohydrodynamics gyrokinetic simulation model has been derived analytically by taking into account both thermal ion compressibility and diamagnetic effects in addition to energetic particle kinetic behaviors. The extended model has been used for implementing an extended version of hybrid magnetohydrodynamics gyrokinetic code (XHMGC) to study thermal ion kinetic effects on Alfvenic modes driven by energetic particles, such as kinetic beta induced Alfven eigenmodes in tokamak fusion plasmas. The XHMGC nonlinear model can be used to address a number of problems, where kinetic treatments of both thermal and supra-thermal plasma components are necessary, as theoretically predicted, or where it is desirable to investigate the phenomena connected with the presence of two supra-thermal particle species with different radial profiles and velocity space distributions.

  7. Reappraising Transition Region Line Widths in light of Recent Alfv\\'{e}n Wave Discoveries

    CERN Document Server

    McIntosh, Scott W; Tarbell, Theodore D

    2008-01-01

    We provide a new interpretation of ultraviolet transition region emission line widths observed by the SUMER instrument on the Solar and Heliospheric Observatory (SOHO). This investigation is prompted by observations of the chromosphere at unprecedented spatial and temporal resolution from the Solar Optical Telescope (SOT) on Hinode revealing that all chromospheric structures above the limb display significant transverse (Alfvenic) perturbations. We demonstrate that the magnitude, network sensitivity and apparent center-to-limb isotropy of the measured line widths (formed below 250,000K) can be explained by an observationally constrained forward-model in which the line width is caused by the line-of-sight superposition of longitudinal and Alfvenic motions on the small-scale (spicular) structures that dominate the chromosphere and low transition region.

  8. Effects of the stratification of two diffusive component and the magnetic field on the existence of internal Alfven gravity waves in a turbulent flow

    International Nuclear Information System (INIS)

    The mechanism of momentum and energy transfer by internal Alfven-gravity waves is studied in a turbulent plasma flow, modelling astrophysical and geophysical situations. The difficulty of the indeterminate system of equations is solved by using gradient diffusion model as a suitable closure. It is found that the weak stratification and the magnetic field decrease the intensity of the turbulence. (D.Gy.)

  9. Coronal heating and wind acceleration by nonlinear Alfvén waves ? global simulations with gravity, radiation, and conduction

    OpenAIRE

    Suzuki, T. K.

    2008-01-01

    We review our recent results of global one-dimensional (1-D) MHD simulations for the acceleration of solar and stellar winds. We impose transverse photospheric motions corresponding to the granulations, which generate outgoing Alfvén waves. We treat the propagation and dissipation of the Alfvén waves and consequent heating from the photosphere by dynamical simulations in a self-consistent manner. Nonlinear dissipation of Alfven waves becomes quite effective owing to the stratification of the ...

  10. Heat Wave Safety Checklist

    Science.gov (United States)

    ... itself. ❏ Signs of heat stroke include hot, red skin which may be dry or moist; changes in consciousness; vomiting; and high body temperature. ❏ Heat stroke is life-threatening. Call 9-1-1 or ...

  11. Three Dimensional MHD Wave Propagation and Conversion to Alfven Waves near the Solar Surface. I. Direct Numerical Solution

    OpenAIRE

    Cally, P. S.; Goossens, M

    2007-01-01

    The efficacy of fast/slow MHD mode conversion in the surface layers of sunspots has been demonstrated over recent years using a number of modelling techniques, including ray theory, perturbation theory, differential eigensystem analysis, and direct numerical simulation. These show that significant energy may be transferred between the fast and slow modes in the neighbourhood of the equipartition layer where the Alfven and sound speeds coincide. However, most of the models so far have been two...

  12. ICRF heating and wave generation in the ATC tokamak. Part 1: wave generation, propagation and absorption

    International Nuclear Information System (INIS)

    Experimental results and their theoretical interpretations of rf heating experiments in the ion cyclotron range of frequencies are presented. The presentation is in two parts, with this part describing the experimental facilities and characteristics of fast compressional Alfven waves in the tokamak, and a subsequent paper which will deal with the pricipal heating results. It is shown that a simple coupling structure which consists essentially of a semi-circular metal strip and a pair of bumper limiters is sufficient to efficiently couple rf power to the plasma. The major part of the coupled power is radiated as the fast wave, and there is no evidence that parasitic loading, if any, accounts for a significant amount of the power. A coupling efficiency (net coupled power/incident power) in excess of 90% is routinely obtained

  13. The Alfven wave spectrum of analytic high-beta tokamak equilibria

    International Nuclear Information System (INIS)

    This thesis addresses a number of problems regarding the equilibrium and stability of a tokamak plasma under fusion conditions. To get insight into the geometric effects on the behaviour of the most prominent global modes, a spectral study was carried out on a class of analytic, noncircular plasma equilibria. Parallel to this work, extending a previous high-beta energy principle a variational principle is developed for the numerical determination of the Alfven spectrum of a high-beta tokamak with arbitrary cross-section. Based on the Lagrangian formalism, representations were derived for the potential and kinetic energy in terms of arbitrary, non-orthogonal flux coordinates, which can be readily implemented in a numerical programme. The method is then tested by using the analytic equilibrium as input. 85 refs.; 32 figs.; 2 tabs

  14. Alfv\\'en wave phase mixing in flows -- why over-dense solar coronal open magnetic field structures are cool?

    CERN Document Server

    Tsiklauri, D

    2015-01-01

    Our magnetohydrodynamic (MHD) simulations and analytical calculations show that, when a background flow is present, mathematical expressions for the Alfv\\'en wave (AW) damping via phase mixing are modified by a following substitution $C_A^\\prime(x) \\to C_A^\\prime(x)+V_0^\\prime(x)$, where $C_A$ and $V_0$ are AW phase and the flow speeds and prime denotes derivative in the direction across the background magnetic field. In uniform magnetic field and over-dense plasma structures, in which $C_A$ is smaller compared to surrounding plasma, the flow, that is confined to the structure, in the same direction as the AW, reduces the effect of phase mixing, because on the edges of the structure $C_A^\\prime$ and $V_0^\\prime$ have opposite sign. Thus, the wave damps via phase mixing {\\it slower} compared to the case without the flow. This is the consequence of the co-directional flow reducing the wave front stretching in the transverse direction. Although, the result is generic and is applicable to different laboratory or ...

  15. Proton heating by pick-up ion driven cyclotron waves in the outer heliosphere: Hybrid expanding box simulations

    CERN Document Server

    Hellinger, Petr

    2016-01-01

    Using one-dimensional hybrid expanding box model we investigate properties of the solar wind in the outer heliosphere. We assume a proton-electron plasma with a strictly transverse ambient magnetic field and, beside the expansion, we take into account influence of a continuous injection of cold pick-up protons through the charge-exchange process between the solar wind protons and hydrogen of interstellar origin. The injected cold pick-up protons form a ring distribution function that rapidly becomes unstable and generate Alfv\\'en cyclotron waves. The Alfv\\'en cyclotron waves scatter pick-up protons to a spherical shell distribution function that thickens over that time owing to the expansion-driven cooling. The Alf\\'ven cyclotron waves heat solar wind protons in the perpendicular direction (with respect to the ambient magnetic field) through the cyclotron resonance. At later times, the Alfv\\'en cyclotron waves become parametrically unstable and the generated ion acoustic waves heat protons in the parallel dir...

  16. Trapped particle instability and flute instability in tandem mirror; scale separation closure in Alfven wave turbulence

    International Nuclear Information System (INIS)

    We have constructed a quadratic dispersion relation, in which various MHD and kinetic effects like ion diamagnetism, electron diamagnetism, electron-electron electron-ion collisions, ion Landau-damping, E x B drift and energetic particles are included and treated in a systematic way. The numerical study in which we use the formalism to investigate the two most likely instabilities in tandem mirror machines produced many quantitative and qualitative results about the two modes. We have proposed a physically motivated, non-perturbative closure scheme to deal with some problems in plasma or fluid turbulence. After discussing a few simple analytically tractable applications, we have applied our formalism to a model problem: the shear-Alfven turbulence. The problem is readily solved numerically to obtain the turbulent spectrum with the following features: the calculated spectrum has explicit frequency shift from the linear theory as well as explicit band-broadening in k, ω space; the frequency integrated spectrum obeys a power law in the intermediate k range, i.e., I/sub k/ /approximately/ K/sup -α/, where α approaches the value 2 in the case we studied; and the form of the power law is hardly influenced by changing low-k, high-k damping effects, or by changing the strength of the turbulence. It is very encouraging that this closure scheme is capable of producing essential features associated with a turbulence spectrum. 66 refs., 38 figs

  17. Computing the damping and destabilization of global Alfven waves in tokamaks

    International Nuclear Information System (INIS)

    The role of ideal MHD in magnetic fusion is in the first place to discover magnetic geometries with favourable equilibrium and stability properties. Non-ideal effects cause slower and weaker instabilities leading to enhanced transport and often to violent disruptions. MHD spectroscopy, i.e. the identification of ideal and dissipative MHD modes for the purpose of diagnosing tokamaks and optimising their stability properties, requires a numerical tool which accurately calculates the dissipative MHD spectra for measured equilibria. The new spectral code CASTOR (Complex Alfven Spectrum for TORoidal Plasmas), together with the equilibrium solver HELENA, provides such a tool. In CASTOR, the fluid variables ρ, v, T, and b are discretized by means of a combination of cubic Hermite and quadratic finite elements for the radial direction and Fourier modes for the poloidal coordinate. The equilibrium in non-orthogonal flux coordinates ψ, θ, φ with straight field lines is computed using isoparametric bicubic Hermite elements, resulting in a very accurate representation of the metric elements. Finally, for analysis of JET discharges the equilibrium solver HELENA is interfaced with the equilibrium identification code IDENTC(D). (author) 5 refs., 5 figs

  18. Nonlinear Energetic Particle Transport in the Presence of Multiple Alfvenic Waves in ITER

    CERN Document Server

    Schneller, Mirjam; Briguglio, Sergio

    2015-01-01

    This work presents the results of a multi mode ITER study on Toroidal Alfven Eigenmodes, using the nonlinear hybrid HAGIS-LIGKA model. It is found that main conclusions from earlier studies of ASDEX Upgrade discharges can be transferred to the ITER scenario: global, nonlinear effects are crucial for the evolution of the multi mode scenario. This work focuses on the ITER 15 MA baseline scenario with with a safety factor at the magnetic axis of $q_0 =$ 0.986. The least damped eigenmodes of the system are identified with the gyrokinetic, non-perturbative LIGKA solver, concerning mode structure, frequency and damping. Taking into account all weakly damped modes that can be identified linearly, nonlinear simulations with HAGIS reveal strong multi mode behavior: while in some parameter range, quasi-linear estimates turn out to be reasonable approximations for the nonlinearly relaxed energetic particle profile, under certain conditions low-n TAE branches can be excited. As a consequence, not only grow amplitudes of ...

  19. Ion Bernstein wave heating research

    International Nuclear Information System (INIS)

    Ion Bernstein wave heating (IBWH) utilizes the ion Bernstein wave (IBW), a hot plasma wave, to carry the radio frequency (rf) power to heat tokamak reactor core. Earlier wave accessibility studies have shown that this finite-Larmor-radius (FLR) mode should penetrate into a hot dense reactor plasma core without significant attenuation. Moreover, the IBW's low phase velocity (ω/kperpendicular ∼ VTi much-lt Vα) greatly reduces the otherwise serious wave absorption by the 3.5 MeV fusion α-particles. In addition, the property of IBW's that kperpendicular ρi ∼ 1 makes localized bulk ion heating possible at the ion cyclotron harmonic layers. Such bulk ion heating can prove useful in optimizing fusion reactivity. In another vein, with proper selection of parameters, IBW's can be made subject to strong localized electron Landau damping near the major ion cyclotron harmonic resonance layers. This property can be useful, for example, for rf current drive in the reactor plasma core. This paper discusses this research

  20. Influence of Alfven eigenmodes and ion cyclotron heating on the fast-ion distribution in the ASDEX Upgrade tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Weiland, Markus; Geiger, Benedikt; Bilato, Roberto; Schneider, Philip; Tardini, Giovanni; Lauber, Philipp; Ryter, Francois; Schneller, Mirjam [Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Collaboration: ASDEX Upgrade Team

    2015-05-01

    Fast, supra-thermal ions are created in the tokamak ASDEX Upgrade by neutral beam injection and ion cyclotron resonance heating (ICRH) and they are needed for plasma heating and current drive. A possibility to study them is the spectroscopic observation of line radiation (fast-ion D-alpha, FIDA), which emerges from charge exchange reactions. Here, the fast ions can be distinguished from the thermal particles through there strong Doppler-shift, and their radial density profile can be measured and compared to theoretical models. An analysis of the whole Doppler spectrum yields information about the 2D velocity distribution f(v {sub parallel}, v {sub perpendicular} {sub to}). Observation from different viewing angles allows consequently a tomographic reconstruction of f(v {sub parallel}, v {sub perpendicular} {sub to}). For this purpose, the FIDA diagnostic at ASDEX Upgrade has been extended from two to five views, and the spectrometer setup was improved to allow a simultaneous measurement of blue and red Doppler shifts. These recently developed diagnostic capabilities are used to study changes in the fast-ion distribution, which are caused by Alfven eigenmodes. Moreover, the further acceleration of fast ions through 2{sup nd} harmonic ICRH is investigated and compared to theoretical predictions.

  1. Alfven Eigenmode And Ion Bernstein Wave Studies For Controlling Fusion Alpha Particles

    CERN Document Server

    Franklin, F R

    1999-01-01

    In magnetic confinement fusion reactor plasmas, the charged fusion products (such as alpha particles in deuterium-tritium plasmas) will be the dominant power source, and by controlling these charged fusion products using wave-particle interactions the reactor performance could be optimized. This thesis studies two candidate waves: Mode- Converted Ion Bernstein Waves (MCIBWs) and Alfvé n Eigenmodes (AEs). Rates of MCIBW-driven losses of alpha-like fast deuterons, previously observed in the Tokamak Fusion Test Reactor (TFTR), are reproduced by a new model so that the wave-particle diffusion coefficient can be deduced. The MCIBW power in TFTR is found to be ∼ 1/3 that needed for collisionless alpha particle control...

  2. Alfven solitary waves in nonrelativistic, relativistic, and ultra-relativistic degenerate quantum plasma

    Energy Technology Data Exchange (ETDEWEB)

    Rehman, M. A.; Qureshi, M. N. S. [Department of Physics, GC University, Kachery Road, Lahore 54000 (Pakistan); Shah, H. A. [Department of Physics, Forman Christian College, Ferozepur Road, Lahore 54600 (Pakistan); Masood, W. [COMSATS, Institute of Information Technology, Park Road, Chak Shehzad, Islamabad 44000 (Pakistan); National Centre for Physics (NCP) Shahdra Valley Road, Islamabad (Pakistan)

    2015-10-15

    Nonlinear circularly polarized Alfvén waves are studied in magnetized nonrelativistic, relativistic, and ultrarelativistic degenerate Fermi plasmas. Using the quantum hydrodynamic model, Zakharov equations are derived and the Sagdeev potential approach is used to investigate the properties of the electromagnetic solitary structures. It is seen that the amplitude increases with the increase of electron density in the relativistic and ultrarelativistic cases but decreases in the nonrelativistic case. Both right and left handed waves are considered, and it is seen that supersonic, subsonic, and super- and sub-Alfvénic solitary structures are obtained for different polarizations and under different relativistic regimes.

  3. Heat Waves Pose Big Health Threats

    Science.gov (United States)

    ... https://medlineplus.gov/news/fullstory_159744.html Heat Waves Pose Big Health Threats Kids, elderly among those ... can be inherently dangerous, but the initial heat waves every summer can be particularly perilous to those ...

  4. Alfven Eigenmode And Ion Bernstein Wave Studies For Controlling Fusion Alpha Particles

    CERN Document Server

    Heeter, R F

    1999-01-01

    In magnetic confinement fusion reactor plasmas, the charged fusion products (such as alpha particles in deuterium-tritium plasmas) will be the dominant power source, and by controlling these charged fusion products using wave-particle interactions the reactor performance could be optimized. This thesis studies two candidate waves: Mode-Converted Ion Bernstein Waves (MCIBWs) and Alfvén Eigenmodes (AEs). Rates of MCIBW-driven losses of alpha-like fast deuterons, previously observed in the Tokamak Fusion Test Reactor (TFTR), are reproduced by a new model so that the wave-particle diffusion coefficient can be deduced. The MCIBW power in TFTR is found to be ∼ 1/3 that needed for collisionless alpha particle control. A reasonable reactor power scaling is derived. To study AEs, existing magnetic fluctuation probes at the Joint European Torus (JET) have been absolutely calibrated from 30–500 kHz for the first time, allowing fluctuation measurements with &vbm0;dBpol&vbm0;/B0&am...

  5. Dissipation of Alfven wave pulses propagating along dipole magnetic tubes with reflections at the ionosphere

    NARCIS (Netherlands)

    Erkaev, NV; Shaidurov, VA; Semenov, VS; Biernat, HK; Heidorn, D; Lakhina, GS

    2006-01-01

    A ratio of the maximal and minimal cross sections of the magnetic tube (contraction ratio) is a crucial parameter which affects very strongly on reflections of MHD wave pulses propagating along a narrowing magnetic flux tube. In cases of large contraction ratios of magnetospheric magnetic tubes, the

  6. An extended hybrid magnetohydrodynamics gyrokinetic model for numerical simulation of shear Alfv\\'en waves in burning plasmas

    CERN Document Server

    Wang, X; Chen, L; Di Troia, C; Fogaccia, G; Vlad, G; Zonca, F

    2010-01-01

    Adopting the theoretical framework for the generalized fishbonelike dispersion relation, an extended hybrid magnetohydrodynamics gyrokinetic simulation model has been derived analytically by taking into account both thermal ion compressibility and diamagnetic effects in addition to energetic particle kinetic behaviors. The extended model has been used for implementing an eXtended version of Hybrid Magnetohydrodynamics Gyrokinetic Code (XHMGC) to study thermal ion kinetic effects on Alfv\\'enic modes driven by energetic particles, such as kinetic beta induced Alfv\\'en eigenmodes in tokamak fusion plasmas.

  7. Review of tokamak experiments on direct electron heating and current drive with fast waves

    International Nuclear Information System (INIS)

    Results from tokamak experiments on direct electron interaction with the compressional Alfven wave (open-quote fast wave close-quote) are reviewed. Experiments aimed at electron heating as well as those in which fast wave electron current drive was investigated are discussed. A distinction is drawn between experiments employing the lower hybrid range of frequencies, where both the lower hybrid wave (open-quote slow wave close-quote) and the fast wave can propagate in much of the plasma, and those experiments using the fast wave in the range of moderate to high ion cyclotron harmonics, where only the fast wave can penetrate to the plasma core. Most of the early tokamak experiments were in the lower hybrid frequency regime, and the observed electron interaction appeared to be very similar to that obtained with the slow wave at the same frequency. In particular, electron interaction with the fast wave was observed only below a density limit nearly the same as the well known slow wave density limit. In the more recent lower frequency fast wave experiments, electron interaction (heating and current drive) is observed at the center of the discharge, where slow waves are not present

  8. Chiral heat wave and mixed waves in kinetic theory

    CERN Document Server

    Frenklakh, D

    2016-01-01

    We study collective excitations in hot rotating chiral media in presence of magnetic field in kinetic theory, namely Chiral Heat Wave and its' mixings with Chiral Vortical Wave and Chiral Magnetic Wave. Our results for velocities of these waves have slight alterations from those obtained earlier. We explain the origin of these alterations and also give the most general expressions for the velocities of all these waves in hydrodynamic approach.

  9. Formation of quasiparallel Alfven solitons

    Science.gov (United States)

    Hamilton, R. L.; Kennel, C. F.; Mjolhus, E.

    1992-01-01

    The formation of quasi-parallel Alfven solitons is investigated through the inverse scattering transformation (IST) for the derivative nonlinear Schroedinger (DNLS) equation. The DNLS has a rich complement of soliton solutions consisting of a two-parameter soliton family and a one-parameter bright/dark soliton family. In this paper, the physical roles and origins of these soliton families are inferred through an analytic study of the scattering data generated by the IST for a set of initial profiles. The DNLS equation has as limiting forms the nonlinear Schroedinger (NLS), Korteweg-de-Vries (KdV) and modified Korteweg-de-Vries (MKdV) equations. Each of these limits is briefly reviewed in the physical context of quasi-parallel Alfven waves. The existence of these limiting forms serves as a natural framework for discussing the formation of Alfven solitons.

  10. An extended hybrid magnetohydrodynamics gyrokinetic model for numerical simulation of shear Alfv\\'en waves in burning plasmas

    OpenAIRE

    Wang, X.; Briguglio, S.; Chen, L.; Di Troia, C; Fogaccia, G.; Vlad, G.; Zonca, F.

    2010-01-01

    Adopting the theoretical framework for the generalized fishbonelike dispersion relation, an extended hybrid magnetohydrodynamics gyrokinetic simulation model has been derived analytically by taking into account both thermal ion compressibility and diamagnetic effects in addition to energetic particle kinetic behaviors. The extended model has been used for implementing an eXtended version of Hybrid Magnetohydrodynamics Gyrokinetic Code (XHMGC) to study thermal ion kinetic effects on Alfv\\'enic...

  11. Wave Heating of the Solar Chromosphere

    Indian Academy of Sciences (India)

    Wolfgang Kalkofen

    2008-03-01

    The nonmagnetic interior of supergranulation cells has been thought since the 1940s to be heated by the dissipation of acoustic waves. But all attempts to measure the acoustic flux have failed to show sufficient energy for chromospheric heating. Recent space observations with TRACE, for example, have found 10% or less of the necessary flux. To explain the missing energy it has been speculated that the nonmagnetic chromosphere is heated mainly by waves related to the magnetic field. If that were correct, the whole chromosphere, magnetic as well as nonmagnetic, would be heated mainly by waves related to the magnetic field. But contrary to expectation, the radiation emerging from the nonmagnetic chromosphere shows none of the signatures of magnetic waves, only those of acoustic waves. Nearly all the heating of the nonmagnetic chromosphere must therefore be due to acoustic waves. In the magnetic network on the boundary of supergranulation cells, on the other hand, the small filling factor of the magnetic field in the photosphere implies that only a small fraction of the wave flux that travels upward to heat the chromosphere can be channeled by the magnetic field. Hence, while some of the energy that is dissipated in the magnetic network is in the form of magnetic waves, most of it must be in the form of acoustic waves. Thus, the quiet solar chromosphere, instead of being heated mainly by magneticwaves throughout, must be heated mainly by acoustic waves throughout. The full wave flux heating the quiet chromosphere must travel through the photosphere. In the nonmagnetic medium, this flux is essentially all in the form of acoustic waves; TRACE registers at most 10% of it, perhaps because of limited spatial resolution.

  12. Heating Cooling Flows with Weak Shock Waves

    OpenAIRE

    Mathews, W. G.; Faltenbacher, A.; Brighenti, F

    2005-01-01

    The discovery of extended, approximately spherical weak shock waves in the hot intercluster gas in Perseus and Virgo has precipitated the notion that these waves may be the primary heating process that explains why so little gas cools to low temperatures. This type of heating has received additional support from recent gasdynamical models. We show here that outward propagating, dissipating waves deposit most of their energy near the center of the cluster atmosphere. Consequently, if the gas i...

  13. Chiral Heat Wave and wave mixing in chiral media

    CERN Document Server

    Chernodub, M N

    2016-01-01

    We show that a hot rotating fluid of relativistic chiral fermions possesses a new gapless collective excitation associated with coherent propagation of energy density and chiral density waves along the axis of rotation. This excitation, which we call the Chiral Heat Wave, emerges due to a mixed gauge-gravitational anomaly. At finite density the Chiral Heat Wave couples to the Chiral Vortical Wave while in the presence of an external magnetic field it mixes with the Chiral Magnetic Wave. We find that the coupled waves - which are coherent fluctuations of the vector, axial and energy currents - have generally different velocities compared to the velocities of the individual waves. We also demonstrate that rotating chiral systems subjected to external magnetic field possess non-propagating metastable thermal excitations, the Dense Hot Spots.

  14. On The Role of MHD Waves in Heating Localised Magnetic Structures

    Science.gov (United States)

    Erdélyi, R.; Nelson, C. J.

    2016-04-01

    Satellite and ground-based observations from e.g. SOHO, TRACE, STEREO, Hinode, SDO and IRIS to DST/ROSA, IBIS, CoMP, STT/CRISP have provided a wealth of evidence of waves and oscillations present in a wide range of spatial scales of the magnetised solar atmosphere. Our understanding about localised solar structures has been considerably changed in light of these high spatial and time resolution observations. However, MHD waves not only enable us to perform sub-resolution magneto-seismology of magnetic waveguides but are also potential candidates to carry and damp the necessary non-thermal energy in these localised waveguides. First, we will briefly outline the basic recent developments in MHD wave theory focussing on linear waves. Next, we discuss the role of the most frequently studied wave classes, including the Alfven, and magneto-acoustic kink and sausage waves. The current theoretical (and often difficult) interpretations of the detected solar atmospheric wave and oscillatory phenomena within the framework of MHD will be shown. Last, the latest reported observational findings of potential MHD wave flux, in terms of localised plasma heating, in the solar atmosphere is discussed, bringing us closer to solve the coronal heating problem.

  15. Waves in Space Plasmas

    International Nuclear Information System (INIS)

    Applications of linear mode conversion at Alfven/ion-ion hybrid resonances and at electron plasma frequency have been discussed. Alfven resonances play an important role on energy transport the outer to inner regions of magnetospheres. At Earth's magnetopause, the mode-converted kinetic Alfven waves also lead to solar wind particle entry and transverse ion heating. IIH resonant waves can explain of the generation of linearly polarized EMIC waves at Earth. Compressional waves can also interact with Mercury's magnetosphere exciting IIH resonances as global eigenmodes. Linear mode conversion (LMC) from Langmuir to electromagnetic waves is relevant to explain type II and III radio bursts. Through the LMC, both right- and left-hand polarized wave modes are produced and it provides the solutions for linear/partial polarized type II and III problems.

  16. Kinetic Damping of Toroidal Alfven Eigenmodes

    Energy Technology Data Exchange (ETDEWEB)

    G.Y. Fu; H.L. Berk; A. Pletzer

    2005-05-03

    The damping of Toroidal Alfven Eigenmodes in JET plasmas is investigated by using a reduced kinetic model. Typically no significant damping is found to occur near the center of the plasma due to mode conversion to kinetic Alfven waves. In contrast, continuum damping from resonance near the plasma edge may be significant, and when it is, it gives rise to damping rates that are compatible with the experimental observations.

  17. Low-n shear Alfven spectra in axisymmetric toroidal plasmas

    International Nuclear Information System (INIS)

    In toroidal plasmas, the toroidal magnetic field is nonuniform over a magnetic surface and causes coupling of different poloidal harmonics. It is shown both analytically and numerically that the toroidicity not only breaks up the shear Alfven continuous spectrum, but also creates new, discrete, toroidicity-induced shear Alfven eigenmodes with frequencies inside the continuum gaps. Potential applications of the low-n toroidicity-induced shear Alfven eigenmodes on plasma heating and instabilities are addressed. 17 refs., 4 figs

  18. The Plausibility of the Stationary Inertial Alfven Wave in Explaining Important Morphological and Temporal Signatures of Auroral Arcs based on Laboratory Experiments and Auroral Observations

    Science.gov (United States)

    Nogami, S. H.; Koepke, M. E.; Gillies, D. M.; Knudsen, D. J.; Vincena, S. T.; Van Compernolle, B.; Donovan, E.

    2015-12-01

    The Stationary Inertial Alfven Wave (StIAW) [Knudsen J. Geophys. Res., 101, 10761 (1996)] is a non-fluctuating, non-travelling, spatially periodic pattern in electromagnetic field and fluid quantities that arises in the simultaneous presence of a magnetic-field-aligned current channel and cross-magnetic field plasma flow. Theory predicts [Finnegan et al., Nonlin. Proc. Geophys., 15, 957 (2008)] that the wave appears as an ion density perturbation that is static in the laboratory frame and that the wave electric field can accelerate electrons parallel to a background magnetic field. For experiments in the afterglow plasma in LAPD-U, results of which are reported on in this poster, the necessary conditions for the stationary wave are generated by a biased segmented electrode that creates a convective flow and a planar-mesh electrode that draws current parallel to the background magnetic field. An electrostatic probe and a retarding field energy analyzer measure fixed (in the laboratory frame) patterns in the ion density and electron energy. Spatial patterns of electron acceleration are reminiscent of the patterns present during the formation of discrete auroral arcs. Observation of long-lived discrete arcs indicates that some arcs require a generation mechanism that supports electron acceleration parallel to auroral field lines for tens of minutes. We present arc lifetime statistics to emphasize the paucity of physical models that explain these observations. *Support from NSF grant PHY-130-1896 and grants from the Canadian Space Agency is gratefully acknowledged. We also thank the THEMIS ASI Teams at U Calgary and UC Berkeley.

  19. Electric Field Observations of Plasma Convection, Shear, Alfven Waves, and other Phenomena Observed on Sounding Rockets in the Cusp and Boundary Layer

    Science.gov (United States)

    Pfaff, R. F.

    2009-01-01

    On December 14,2002, a NASA Black Brant X sounding rocket was launched equatorward from Ny Alesund, Spitzbergen (79 N) into the dayside cusp and subsequently cut across the open/closed field line boundary, reaching an apogee of771 km. The launch occurred during Bz negative conditions with strong By negative that was changing during the flight. SuperDarn (CUTLASS) radar and subsequent model patterns reveal a strong westward/poleward convection, indicating that the rocket traversed a rotational reversal in the afternoon merging cell. The payload returned DC electric and magnetic fields, plasma waves, energetic particle, suprathermal electron and ion, and thermal plasma data. We provide an overview of the main observations and focus on the DC electric field results, comparing the measured E x B plasma drifts in detail with the CUTLASS radar observations of plasma drifts gathered simultaneously in the same volume. The in situ DC electric fields reveal steady poleward flows within the cusp with strong shears at the interface of the closed/open field lines and within the boundary layer. We use the observations to discuss ionospheric signatures of the open/closed character of the cusp/low latitude boundary layer as a function of the IMF. The electric field and plasma density data also reveal the presence of very strong plasma irregularities with a large range of scales (10 m to 10 km) that exist within the open field line cusp region yet disappear when the payload was equatorward of the cusp on closed field lines. These intense low frequency wave observations are consistent with strong scintillations observed on the ground at Ny Alesund during the flight. We present detailed wave characteristics and discuss them in terms of Alfven waves and static irregularities that pervade the cusp region at all altitudes.

  20. Heat waves, aging, and human cardiovascular health.

    Science.gov (United States)

    Kenney, W Larry; Craighead, Daniel H; Alexander, Lacy M

    2014-10-01

    This brief review is based on a President's Lecture presented at the Annual Meeting of the American College of Sports Medicine in 2013. The purpose of this review was to assess the effects of climate change and consequent increases in environmental heat stress on the aging cardiovascular system. The earth's average global temperature is slowly but consistently increasing, and along with mean temperature changes come increases in heat wave frequency and severity. Extreme passive thermal stress resulting from prolonged elevations in ambient temperature and prolonged physical activity in hot environments creates a high demand on the left ventricle to pump blood to the skin to dissipate heat. Even healthy aging is accompanied by altered cardiovascular function, which limits the extent to which older individuals can maintain stroke volume, increase cardiac output, and increase skin blood flow when exposed to environmental extremes. In the elderly, the increased cardiovascular demand during heat waves is often fatal because of increased strain on an already compromised left ventricle. Not surprisingly, excess deaths during heat waves 1) occur predominantly in older individuals and 2) are overwhelmingly cardiovascular in origin. Increasing frequency and severity of heat waves coupled with a rapidly growing at-risk population dramatically increase the extent of future untoward health outcomes. PMID:24598696

  1. Dispersion relation on the collective models of Alfven wave resonant heating

    International Nuclear Information System (INIS)

    By considering the magnetic compressibility it is shown that, for a theta pinch type plasma, the m=1 collective mode could be cut off. This is in contrast with the results based on an incompressible fluid model. This restricts the collective mode to a small region of k space near zero. (Author)

  2. Experimental observation of radiation heat waves

    Institute of Scientific and Technical Information of China (English)

    DingYao-Nan; YaoZhen-Yu; 等

    1997-01-01

    Radiation heat waves play an important role in high-temperature hydrodrnamic phenomena which is very important for laser fusion.Therefore,the propagation of a radiation heat wave through a thin foil of solid aluminium is observed.The wave is driven by the intense solft-X-ray radiation in a cylindrical cavity heated by the intense laser pulse.Experiments are carried out with two beams of λ=1.05μm light form the Shenguang Nd-glass laser facility.The pulse energy is about 600 J and the pulse duration 0.8ns.Evidence of radiation heat wave is obtained by observing the delayes signal of intense thermal emission from the outside of the foil.The delay is 850ps for 1.5μm thick foil and the mass ablation rate is about 4.8×105g/(cm2.s) under the X-ray flux of about 1×1013W/cm2.Also.the radiation-driven shock waves of (2±1)TPa are observed from different shots in the experiments.

  3. On the Definition of a Heat Wave.

    Science.gov (United States)

    Robinson, Peter J.

    2001-04-01

    Heat waves are a major cause of weather-related deaths. With the current concern for global warming it is reasonable to suppose that they may increase in frequency, severity, duration, or areal extent in the future. However, in the absence of an adequate definition of a heat wave, it is impossible to assess either changes in the past or possible consequences for the future. A set of definitions is proposed here, based on the criteria for heat stress forecasts developed by the National Weather Service (NWS). Watches or warnings are issued when thresholds of daytime high and nighttime low heat index (Hi) values are exceeded for at least two consecutive days. The heat index is a combination of ambient temperature and humidity that approximates the environmental aspect of the thermal regime of a human body, with the NWS thresholds representing a generalized estimate of the onset of physiological stress. These thresholds cannot be applied directly nationwide. In hot and humid regions, physical, social, and cultural adaptations will require that the thresholds be set higher to ensure that only those events perceived as stressful are identified. In other, cooler, areas the NWS criteria may never be reached even though unusually hot events may be perceived as heat waves. Thus, it is likely that a similar number of perceived heat events will occur in all regions, with the thresholds varying regionally. Hourly Hi for 178 stations in the coterminous United States was analyzed for the 1951-90 period to determine appropriate threshold criteria. Use of the NWS criteria alone indicated that much of the nation had less than three heat waves per decade, and this value was adopted as the baseline against which to establish suitable thresholds. For all areas, a percentile threshold approach was tested. Using all available data, daytime high and nighttime low thresholds were established separately for each specific percentile. Heat waves were treated as occurring when conditions

  4. HEAT WAVES, AGING, AND HUMAN CARDIOVASCULAR HEALTH

    OpenAIRE

    Kenney, W. Larry; Craighead, Daniel H.; Alexander, Lacy M.

    2014-01-01

    This brief review is based on a President’s Lecture presented at the Annual Meeting of the American College of Sports Medicine in 2013. The purpose of this review is to assess the effects of climate change and consequent increases in environmental heat stress on the aging cardiovascular system. The earth’s average global temperature is slowly but consistently increasing, and along with mean temperature changes come increases in heat wave frequency and severity. Extreme passive thermal stress ...

  5. Climate Change Effects on Heat Waves and Future Heat Wave-Associated IHD Mortality in Germany

    Directory of Open Access Journals (Sweden)

    Stefan Zacharias

    2014-12-01

    Full Text Available The influence of future climate change on the occurrence of heat waves and its implications for heat wave-related mortality due to ischemic heart diseases (IHD in Germany is studied. Simulations of 19 regional climate models with a spatial resolution of 0.25° × 0.25° forced by the moderate climate change scenario A1B are analyzed. Three model time periods of 30 years are evaluated, representing present climate (1971–2000, near future climate (2021–2050, and remote future climate (2069–2098. Heat waves are defined as periods of at least three consecutive days with daily mean air temperature above the 97.5th percentile of the all-season temperature distribution. Based on the model simulations, future heat waves in Germany will be significantly more frequent, longer lasting and more intense. By the end of the 21st century, the number of heat waves will be tripled compared to present climate. Additionally, the average duration of heat waves will increase by 25%, accompanied by an increase of the average temperature during heat waves by about 1 K. Regional analyses show that stronger than average climate change effects are observed particularly in the southern regions of Germany. Furthermore, we investigated climate change impacts on IHD mortality in Germany applying temperature projections from 19 regional climate models to heat wave mortality relationships identified in a previous study. Future IHD excess deaths were calculated both in the absence and presence of some acclimatization (i.e., that people are able to physiologically acclimatize to enhanced temperature levels in the future time periods by 0% and 50%, respectively. In addition to changes in heat wave frequency, we incorporated also changes in heat wave intensity and duration into the future mortality evaluations. The results indicate that by the end of the 21st century the annual number of IHD excess deaths in Germany attributable to heat waves is expected to rise by factor 2

  6. Northern Eurasian Heat Waves and Droughts

    Science.gov (United States)

    Schubert, Siegfried; Wang, Hailan; Koster, Randal; Suarez, Max; Groisman, Pavel

    2013-01-01

    This article reviews our understanding of the characteristics and causes of northern Eurasian summertime heat waves and droughts. Additional insights into the nature of temperature and precipitation variability in Eurasia on monthly to decadal time scales and into the causes and predictability of the most extreme events are gained from the latest generation of reanalyses and from supplemental simulations with the NASA GEOS-5 AGCM. Key new results are: 1) the identification of the important role of summertime stationary Rossby waves in the development of the leading patterns of monthly Eurasian surface temperature and precipitation variability (including the development of extreme events such as the 2010 Russian heat wave), 2) an assessment of the mean temperature and precipitation changes that have occurred over northern Eurasia in the last three decades and their connections to decadal variability and global trends in SST, and 3) the quantification (via a case study) of the predictability of the most extreme simulated heat wave/drought events, with some focus on the role of soil moisture in the development and maintenance of such events. A literature survey indicates a general consensus that the future holds an enhanced probability of heat waves across northern Eurasia, while there is less agreement regarding future drought, reflecting a greater uncertainty in soil moisture and precipitation projections. Substantial uncertainties remain in our understanding of heat waves and drought, including the nature of the interactions between the short-term atmospheric variability associated with such extremes and the longer-term variability and trends associated with soil moisture feedbacks, SST anomalies, and an overall warming world.

  7. Damping of Energetic-Particle-Driven Alfven Eigenmodes in Different Magnetic Equilibria in the MST Reversed-Field Pinch

    Science.gov (United States)

    Sears, Stephanie; Anderson, Jay; Capecchi, William; Bonofiglo, Phillip; Kim, Jungha

    2015-11-01

    Alfven wave dissipation is an important mechanism behind anomalous ion heating, both in astrophysical and reversed-field pinch (RFP) plasma systems. Additionally, the damping rate has implications for the stability of energetic particle driven modes (EPMs) and their associated nonlinear dynamics and fast ion transport, which are crucial topics for any burning plasma reactor. With a 1 MW neutral beam injector on the MST RFP, a controlled set of EPMs and Alfvenic eigenmodes can be driven in this never-before-probed region of strong magnetic shear and weak externally applied magnetic field. The decay time of the average of 100s of reproducible bursts is computed for different equilibrium profiles. In this work, we report initial measurements of Alfvenic damping rates with varied RFP equilibria (including magnetic shear and flow shear) and the effects on fast ion transport. This research is supported by DOE and NSF.

  8. Non-linear study of fast particle excitation of global Alfven eigenmodes during ICRH

    International Nuclear Information System (INIS)

    Full text: Fast ions created by ICRH have been proposed for simulating alpha particle heating. In order to extrapolate results regarding excitation of global Alfven eigenmodes to that of thermonuclear alpha particles it is important to understand the differences between excitation by ICRH and by thermonuclear alpha particles. ICRH does not only produce strong anisotropic distribution functions of the resonant ion species compared to the nearly isotropic one of thermonuclear alpha particles, but also decorrelates the interactions between the high-energy ions and the global Alfven eigenmode. In absence of decorrelation the resonant ions will make superadiabatic oscillations in energy. The decorrelation caused by collisions and RF interactions leads to an effective broadening of the MHD resonant region hence increasing the extent of the energy transport region in phase space. The decorrelations also affect the growth rate and the amplitude of the saturation level. ICRH decorrelates the MHD interactions and pushes ions in and out of resonance with the Alfven wave leading to enhanced excitation or damping of the mode. The decorrelation by Coulomb collisions decreases with energy and is more important for particles with low energy, whereas the decorrelation by ICRH becomes more important for high-energy particles. A method to calculate the distribution function of the resonant ions and amplitude of the global Alfven wave self-consistently during ICRH has been developed and implemented in the SELFO- code. The SELFO code consists of the orbit averaged Monte Carlo code FIDO for calculating the distribution function of the heated ions and the global wave code LION for calculating the wave field for ICRF heating. Self-consistent calculations of the ICRF wave field and distribution function is carried out by solving the wave field in LION with a dielectric tensor calculated from the global distribution function obtained with the FIDO code. The wave field of the global Alfven

  9. Kinetic Alfven solitons in a low-beta plasma

    International Nuclear Information System (INIS)

    Kinetic Alfven solitons with hot electrons and finite electron inertia in a low beta (β=8πnoT/B2G, the ratio of the kinetic to the magnetic pressure) plasma is studied analytically, with the ion motion being considered dominant through the polarization drift. Both compressive and rarefactive kinetic Alfven solitons are found to exist within a definite range of kz (the direction of propagation of the kinetic Alfven solitary waves with respect to the direction of the magnetic field) for each pair of assigned values of β and M (Mach number). Unlike in previous theoretical investigations, β appears as an explicit parameter for the kinetic Alfven solitons in this case. In addition, consideration of the electron pressure gradient is found to suppress the speed of both the Alfven solitons considerably for A (=2QM2 / βk2z, with Q the electron-to-ion mass ratio) less than unity. (Author)

  10. Elastic Waves And Their Conversion Due To Heating

    Directory of Open Access Journals (Sweden)

    S. B. Srivastava

    1973-04-01

    Full Text Available The purpose of this paper is to consider the effect of thermal waves on solids producing thereby elastic waves and the secondary thermal waves, conversion of elastic waves into electromagnetic waves and their application to Defence problems, for example, projection of rockets and missiles. The investigation is restricted to the case when neither melting nor evaporation takes place during heat supply.

  11. Statistical Evidence for the Existence of Alfv\\'enic Turbulence in Solar Coronal Loops

    CERN Document Server

    Liu, Jiajia; De Moortel, Ineke; Threlfall, James; Bethge, Christian

    2014-01-01

    Recent observations have demonstrated that waves which are capable of carrying large amounts of energy are ubiquitous throughout the solar corona. However, the question of how this wave energy is dissipated (on which time and length scales) and released into the plasma remains largely unanswered. Both analytic and numerical models have previously shown that Alfv\\'enic turbulence may play a key role not only in the generation of the fast solar wind, but in the heating of coronal loops. In an effort to bridge the gap between theory and observations, we expand on a recent study [De Moortel et al., ApJL, 782:L34, 2014] by analyzing thirty-seven clearly isolated coronal loops using data from the Coronal Multi-channel Polarimeter (CoMP) instrument. We observe Alfv\\'enic perturbations with phase speeds which range from 250-750 km/s and periods from 140-270 s for the chosen loops. While excesses of high frequency wave-power are observed near the apex of some loops (tentatively supporting the onset of Alfv\\'enic turbu...

  12. Radiation Heat Waves in Gold Plasma

    Institute of Scientific and Technical Information of China (English)

    YANG Jia-Min; XU Yan; DING Yao-Nan; LAI Dong-Xian; DING Yong-Kun; JIANG Shao-En; ZHENG Zhi-Jian; MIAO Wen-Yong

    2003-01-01

    Eight beams 0.35/um laser with pulse duration of about 1.0ns and energy of 260 J per beam was injected into a cylindrical cavity to generate intense x-ray radiation on the "Shengguang I" high power laser facility. Gold foils with a thickness in the range of 0.09-0.52/j,m were attached on the diagnostic hole of the cavity and ablated by the intense x-ray radiation. The propagating radiation heat wave in the high-Z gold plasma was observed clearly. For comparison, we also simulated the experimental results.

  13. Kinetic Thermal Ions Effects on Alfvenic Fluctuations in Tokamak Plasmas

    International Nuclear Information System (INIS)

    Full text: The early observation of beta induced Alfven eigenmodes (BAE) and a variety of recent experimental observations have attracted attention on studying the low-frequency Alfvenic fluctuations in tokamaks. The generalized fishbone-like dispersion relation theoretical framework has been adopted for extending the hybrid model by taking into account both thermal ion compressibility and diamagnetic effects in addition to energetic particles (EP) kinetic behaviours. The extended model has been used for implementing an eXtended version of HMGC (XHMGC). In general, the new version of HMGC can have two species of kinetic particles. On one hand, one can use XHMGC for investigating thermal ion kinetic effects on Alfvenic modes driven by EP. In this case, EP dynamics contribute in the ideal MHD region; while wave-particle resonances with core-plasma ions are important only in a narrow inertial layer centred about the mode rational surface, where the dynamics of EP can be neglected due to their large perpendicular orbits (compared to the layer width). On the other hand, it may be interesting to use XHMGC as a tool to simulate two coexisting EP species, generated e.g. by both ICRH and NBI heating, in order to study linear excitation of Alfvenic fluctuations and Energetic Particle Modes (EPM), as well as the interplay between the respective nonlinear physics. Results of initial-value simulations show that the observed frequency is always slightly higher than the BAE accumulation point and is the same at different radial positions; consistent with the characteristics of a discrete BAE-SAW eigenmode (termed as kinetic BAE or KBAE); however, no discrete eigenmode is found within the gap when MHD is ideally stable. Meanwhile, preliminary simulations of KBAE/EPM driven by purely circulating EP have also been done. So far, the results show that the mode frequency is higher than either theoretical BAE accumulation point frequency or EP transit frequency, and increases with

  14. Heat Waves, Urban Vegetation, and Air Pollution

    Science.gov (United States)

    Churkina, G.; Grote, R.; Butler, T. M.

    2014-12-01

    Fast-track programs to plant millions of trees in cities around the world aim at the reduction of summer temperatures, increase carbon storage, storm water control, provision of space for recreation, as well as poverty alleviation. Although these multiple benefits speak positively for urban greening programs, the programs do not take into account how close human and natural systems are coupled in urban areas. Elevated temperatures together with anthropogenic emissions of air and water pollutants distinguish the urban system. Urban and sub-urban vegetation responds to ambient changes and reacts with pollutants. Neglecting the existence of this coupling may lead to unforeseen drawbacks of urban greening programs. The potential for emissions from urban vegetation combined with anthropogenic emissions to produce ozone has long been recognized. This potential increases under rising temperatures. Here we investigate how global change induced heat waves affect emissions of volatile organic compounds (VOC) from urban vegetation and corresponding ground-level ozone levels. We also quantify other ecosystem services provided by urban vegetation (e.g., cooling and carbon storage) and their sensitivity to climate change. In this study we use Weather Research and Forecasting Model with coupled atmospheric chemistry (WRF-CHEM) to quantify these feedbacks in Berlin, Germany during the heat waves in 2003 and 2006. We highlight the importance of the vegetation for urban areas under changing climate and discuss associated tradeoffs.

  15. Heat Wave Changes in the Eastern Mediterranean since 1960

    Science.gov (United States)

    Kuglitsch, Franz G.; Toreti, Andrea; Xoplaki, Elena; Della-Marta, Paul M.; Zerefos, Christos S.; Türkes, Murat; Luterbacher, Jürg

    2010-05-01

    Heat waves have discernible impacts on mortality and morbidity, infrastructure, agricultural resources, the retail industry, ecosystem and tourism and consequently affect human societies. A new definition of socially relevant heat waves is presented and applied to new data sets of high-quality homogenized daily maximum and minimum summer air temperature series from 246 stations in the eastern Mediterranean region (including Albania, Bosnia-Herzegovina, Bulgaria, Croatia, Cyprus, Greece, Israel, Romania, Serbia, Slovenia, Turkey). Changes in heat wave number, length and intensity between 1960 and 2006 are quantified. Daily temperature homogeneity analysis suggest that many instrumental measurements in the 1960s are warm-biased, correcting for these biases regionally averaged heat wave trends are up to 8% higher. We find significant changes across the western Balkans, southwestern and western Turkey, and along the southern Black Sea coastline. Since the 1960s, the mean heat wave intensity, heat wave length and heat wave number across the eastern Mediterranean region have increased by a factor 7.6 ±1.3, 7.5 ±1.3 and 6.2 ±1.1, respectively. These findings suggest that the heat wave increase in this region is higher than previously reported.

  16. Stochastic Ion Heating by the Lower-Hybrid Waves

    Science.gov (United States)

    Khazanov, G.; Tel'nikhin, A.; Krotov, A.

    2011-01-01

    The resonance lower-hybrid wave-ion interaction is described by a group (differentiable map) of transformations of phase space of the system. All solutions to the map belong to a strange attractor, and chaotic motion of the attractor manifests itself in a number of macroscopic effects, such as the energy spectrum and particle heating. The applicability of the model to the problem of ion heating by waves at the front of collisionless shock as well as ion acceleration by a spectrum of waves is discussed. Keywords: plasma; ion-cyclotron heating; shocks; beat-wave accelerator.

  17. Alfven cyclotron instability and ion cyclotron emission

    International Nuclear Information System (INIS)

    Two-dimensional solutions of compressional Alfven eigenmodes (CAE) are studied in the cold plasma approximation. For finite inverse aspect ratio tokamak plasmas the two-dimensional eigenmode envelope is localized at the low magnetic field side with the radial and poloidal localization on the order of a/√m and a/(fourth root of m), respectively, where m is the dominant poloidal mode number. Charged fusion product driven Alfven Cyclotron Instability (ACI) of the compressional Alfven eigenmodes provides the explanation for the ion cyclotron emission (ICE) spectrum observed in tokamak experiments. The ACI is excited by fast charged fusion products via Doppler shifted cyclotron wave-particle resonances. The ion cyclotron and electron Landau dampings and fast particle instability drive are calculated perturbatively for deuterium-deuterium (DD) and deuterium-tritium (DT) plasmas. Near the plasma edge at the low field side the velocity distribution function of charged fusion products is localized in both pitch angle and velocity. The poloidal localization of the eigenmode enhances the ACI growth rates by a factor of √m in comparison with the previous results without poloidal envelope. The thermal ion cyclotron damping determines that only modes with eigenfrequencies at multiples of the edge cyclotron frequency of the background ions can be easily excited and form an ICE spectrum similar to the experimental observations. Theoretical understanding is given for the results of TFTR DD and DT experiments with υα0/υA α0/υA > 1

  18. Explaining Inverted Temperature Loops in the Quiet Solar Corona with Magnetohydrodynamic Wave Mode Conversion

    CERN Document Server

    Schiff, Avery J

    2016-01-01

    Coronal loops trace out bipolar, arch-like magnetic fields above the Sun's surface. Recent measurements that combine rotational tomography, extreme ultraviolet imaging, and potential-field extrapolation have shown the existence of large loops with inverted temperature profiles; i.e., loops for which the apex temperature is a local minimum, not a maximum. These "down loops" appear to exist primarily in equatorial quiet regions near solar minimum. We simulate both these and the more prevalent large-scale "up loops" by modeling coronal heating as a time-steady superposition of: (1) dissipation of incompressible Alfven-wave turbulence, and (2) dissipation of compressive waves formed by mode conversion from the initial population of Alfven waves. We found that when a large percentage (> 99%) of the Alfven waves undergo this conversion, heating is greatly concentrated at the footpoints and stable "down loops" are created. In some cases we found loops with three maxima that are also gravitationally stable. Models th...

  19. Triggering wave-domain heat conduction in graphene

    Science.gov (United States)

    Yao, Wen-Jun; Cao, Bing-Yang

    2016-05-01

    Using non-equilibrium molecular dynamics simulations, we systematically investigate the non-Fourier heat conduction in graphene under steady high heat flux. The results show that if two triggering factors, i.e. steady high heat flux and tensile stress, are satisfied simultaneously, a low-frequency mechanical wave and corresponding wave-like energy profile can be observed, which are distinctly different from ripples and linear temperature profile of the normal Fourier heat conduction. This mechanical wave provides an additional channel of heat transport and renders graphene more conductive without changing its pristine thermal conductivity. What's more, as the heat flux or original bond length increases, its frequency increases and energy transported by this mechanical wave is also on the rise. Further analyses show that such anomalous phenomenon is not arising from the high-energy or high-frequency pulses and also not artifacts of the velocity-exchange method. It is a dissipative structure, a new order state far from thermodynamic equilibrium, and the corresponding nonlinear relationship between the gradient of the wave-like kinetic temperature and the heat flux enables more efficient heat transport in graphene.

  20. Low-Frequency Waves in HF Heating of the Ionosphere

    Science.gov (United States)

    Sharma, A. S.; Eliasson, B.; Milikh, G. M.; Najmi, A.; Papadopoulos, K.; Shao, X.; Vartanyan, A.

    2016-02-01

    Ionospheric heating experiments have enabled an exploration of the ionosphere as a large-scale natural laboratory for the study of many plasma processes. These experiments inject high-frequency (HF) radio waves using high-power transmitters and an array of ground- and space-based diagnostics. This chapter discusses the excitation and propagation of low-frequency waves in HF heating of the ionosphere. The theoretical aspects and the associated models and simulations, and the results from experiments, mostly from the HAARP facility, are presented together to provide a comprehensive interpretation of the relevant plasma processes. The chapter presents the plasma model of the ionosphere for describing the physical processes during HF heating, the numerical code, and the simulations of the excitation of low-frequency waves by HF heating. It then gives the simulations of the high-latitude ionosphere and mid-latitude ionosphere. The chapter also briefly discusses the role of kinetic processes associated with wave generation.

  1. ULF Generation by Modulated Ionospheric Heating

    Science.gov (United States)

    Chang, C.; Labenski, J.; Wallace, T.; Papadopoulos, K.

    2013-12-01

    Modulated ionospheric heating experiments designed to generate ULF waves using the HAARP heater have been conducted since 2007. Artificial ULF waves in the Pc1 frequency range were observed from space and by ground induction magnetometers located in the vicinity of the heater as well as at long distances. Two distinct generation mechanisms of artificial ULF waves were identified. The first was electroject modulation under geomagnetically disturbed conditions. The second was pressure modulation in the E and F regions of the ionosphere under quiet conditions. Ground detections of ULF waves near the heater included both Shear Alfven waves and Magnetosonic waves generated by electrojet and/or pressure modulations. Distant ULF detections involved Magnetosonic wave propagation in the Alfvenic duct with pressure modulation as the most likely source. Summary of our observations and theoretical interpretations will be presented at the meeting. We would like to acknowledge the support provided by the staff at the HAARP facility during our ULF experiments.

  2. Heat transfer intensification using acoustic waves in a cavity

    International Nuclear Information System (INIS)

    The presented paper concerns the idea of using a sound wave to intensify the heat transfer in thermally loaded elements of a gas turbine. The general idea of this type of cooling is described and numerical studies are presented. The applied numerical model is validated based on experimental studies. The research is focused on an improvement in cooling of thermally loaded blade corners. A new concept of the vane internal geometry that improves cooling conditions by generating a sound wave and causing unsteadiness in the flow is compared with the currently used solution. Additionally, a conjugate heat transfer analysis is performed, which allows a better validation of the results. - Highlights: • The idea of using a sound wave to intensify the heat transfer process. • Numerical model and its validation. • Heat transfer assessment based on the fluid flow modelling. • Results of the conjugate heat transfer analysis

  3. 76 FR 62777 - Forum-Trends and Causes of Observed Changes in Heat Waves, Cold Waves, Floods and Drought

    Science.gov (United States)

    2011-10-11

    ... weather and climate events, including heat waves, cold waves, floods, and drought. Participants Will Consider Observed changes and degree of confidence in those changes for heat waves, cold waves, floods, and... National Oceanic and Atmospheric Administration Forum--Trends and Causes of Observed Changes in Heat...

  4. Experimental observation of the shear Alfven resonance in a tokamak

    International Nuclear Information System (INIS)

    Experiments in Tokapole II have demonstrated the shear Alfven resonance in a tokamak by direct probe measurement of the wave magnetic field within the plasma. The resonance is driven by external antennas and is identified as radially localized enhancements of the poloidal wave magnetic field. The radial location agrees with calculations which include toroidicity and noncircularity of the plasma cross-section. Other properties such as polarization, radial width, risetime, and wave enhancement also agree with MHD theory

  5. Novel physics involved in interpretation of Alfvenic activity accompanied by thermal crashes in W7-AS

    International Nuclear Information System (INIS)

    Alfven instabilities driven by fast ions have been observed in many experiments on tokamaks and stellarators. In tokamaks, they can strongly affect the fast ion confinement but not the bulk plasma. In contrast to this, experiments on the Wendelstein 7-AS (W7-AS) stellarator have shown that Alfvenic activity can strongly deteriorate the global energy confinement time: strong thermal crashes (the temperature dropped by up to 30%) were reported in Ref. [1] and observed also in the last series of experiments in 2002. To explain this phenomenon, recently a new mechanism of anomalous electron heat conductivity associated with Kinetic Alfven Waves (KAW) was suggested. In this work, we further develop theory required for the interpretation of experimental observations of Alfvenic activity in W7-AS and analyse a particular shot (No. 34723) where strong drops of the plasma energy content took place in details. As a result, (i) we identified the instability observed in the mentioned W7-AS shot as Non- conventional Global Alfven Eigenmode (NGAE), (ii) suggested an explanation of the frequency chirping (from ∼70 kHz to ∼45 kHz) during the instability bursts, (iii) showed why the instability was most strong at the end of the bursts when thermal crashes occurred, (iv) considered two possible mechanisms of thermal crashes (anomalous heat conductivity and instability-induced-loss of the injected ions), (v) made a modelling of oscillations of the plasma energy content. An important role of the finite orbit width of fast ions was revealed: it was found that finite orbits actually trigger the instability at ω≤ 70 kHz and weaken the mode destabilization at the end of the instability bursts (when ω≥ 40 kHz). It was concluded that the observed frequency chirping can be explained by the expulsion of fast ions from the plasma core and a concomitant local change of the rotational transform. In order to identify the instability, the Alfven continuum and Alfven eigenmodes were

  6. Bulk Ion Heating with ICRF Waves in Tokamaks

    DEFF Research Database (Denmark)

    Mantsinen, M. J.; Bilato, R.; Bobkov, V. V.;

    2015-01-01

    Heating with ICRF waves is a well-established method on present-day tokamaks and one of the heating systems foreseen for ITER. However, further work is still needed to test and optimize its performance in fusion devices with metallic high-Z plasma facing components (PFCs) in preparation of ITER a...

  7. On Heating of Cluster Cooling Flows by Sound Waves

    OpenAIRE

    Fujita, Yutaka; Suzuki, Takeru Ken

    2005-01-01

    We investigate heating of the cool core of a galaxy cluster through the dissipation of sound waves excited by the activities of the central active galactic nucleus (AGN). Using a weak shock theory, we show that this heating mechanism alone cannot reproduce observed temperature and density profiles of a cluster, because the dissipation length of the waves is much smaller than the size of the core and thus the wave energy is not distributed to the whole core. However, we find that if it is comb...

  8. Electron Bernstein Wave Heating and Emission in the TCV Tokamak

    OpenAIRE

    Anja, Mueck; Yann, Camenen; Stefano, Coda; Loïc, Curchod; Timothy P., Goodman; Heinrich P., Laqua; Antoine, Pochelon; Laurie, Porte; Victor S., Udintsev; Francesco, Volpe; Team, TCV

    2007-01-01

    Electron cyclotron resonance heating (ECRH) of high-density tokamak plasmas is limited because of reflections of the waves at so-called wave cutoffs. Electron Bernstein wave (EBW) heating (EBWH) via a double mode conversion process from ordinary (O)-mode, launched from the low field side, to extraordinary (X)-mode and finally to Bernstein (B)-mode offers the possibility of overcoming these density limits. In this paper, the O-X mode conversion dependence on the microwave injection angle is de...

  9. Extreme European heat waves since 1950 with Heat Wave Magnitude Index and their occurrence in the future

    Science.gov (United States)

    Russo, Simone; Dosio, Alessandro; Sillmann, Jana

    2015-04-01

    Heat waves are defined as prolonged periods of extremely hot weather and their magnitude and frequency are expected to increase in the future under climate change. Here we grade the heat waves occurred in Europe since 1950, by means of the Heat Wave Magnitude Index (HWMI) applied to daily maximum temperature from European Observation dataset (E-OBS). As shown in many studies the worst event in the last decades occurred in Russia in 2010. However many other heat waves, as shown here and documented in literature and also in newspapers, occurred in different European regions in the past 64 years. In addition, predictions from ten models from the COordinated Regional climate Downscaling EXperiment (CORDEX) under different IPCC AR5 scenarios, suggest an increased probability of occurrence of extreme heat waves by the end of the century. In particular, under the most severe scenario, events of the same severity, as the 2010 Russian heat wave, will become the norm and are projected to occur as often as every two years in the studied region.

  10. Global structures of Alfven-ballooning modes in magnetospheric plasmas

    International Nuclear Information System (INIS)

    The authors show that a steep plasma pressure gradient can lead to radially localized Alfven modes, which are damped through coupling to filed line resonances. These have been called drift Alfven balloning modes (DABM) and are the prime candidates to explain Pc4-Pc5 geomagnetic pulsations observed during storms. A strong dependence of the damping rate on the azimuthal wave number m is established, as well as on the equilibrium profile. A minimum azimuthal mode number can be found for the DABM to be radially trapped. The authors find that higher m DABMs are better localized, which is consistent with high-m observations

  11. Nonlinear hybrid simulation of toroidicity-induced alfven eigenmode

    International Nuclear Information System (INIS)

    Gyrokinetic/Magnetohydrodynamics hybrid simulations have been carried out using MH3D-K code to study the nonlinear saturation of the toroidicity-induced Alfven eigenmode driven by energetic particles in a tokamak plasma. It is shown that the wave particle trapping is the nonlinear saturation mechanism for the parameters considered. The corresponding density profile flattening of hot particles is observed. The saturation amplitude is proportional to the square of linear growth rate. In addition to TAE modes, a new n = 1, m = 0 global Alfven eigenmode is shown to be excited by the energetic particles

  12. High and low frequency Alfven modes in tokamaks

    International Nuclear Information System (INIS)

    We present an analysis of the typical features of shear Alfven waves in tokamak plasmas in a frequency domain ranging from the ''high'' frequencies (ω ≅ νA/2qR0; νA being the Alfven speed and qR0 the tokamak connection length) of the toroidal gap to the ''low'' frequencies, comparable with the thermal ion diamagnetic frequency, ω*pi and/or the thermal ion transit frequency ωti = νti/qR0 (νti being the ion thermal speed). (author)

  13. An "H-index" for summer heat waves

    Science.gov (United States)

    Teuling, Ryan; Vautard, Robert

    2013-04-01

    Heat waves are among the most severely impacting natural disasters with which we contend. Recent summer "mega-heatwave" extremes in France (2003) and Russia (2010) lead to impacts on ecosystems and economic sectors, as well as increased mortality rates. Appropriate adaptation measures and improved early warning systems are necessary to cope with more frequent phenomena such as those that occurred in the last decade. A simple scale, that allows both identification, definition and ranking of individual heat wave events based on environmental conditions and potential for societal impact, is lacking. Such magnitude scale could also help to evaluate the evolution of heat waves in multi-model climate projections as compared to current climate. A simple index, easy to calculate and communicate, is designed to capture both the intensity and duration of summer heat waves. The index, analogous to the Hirsch index for citations, expresses the magnitude of a heat wave event (H) by the number of subsequent days H over which the daily average apparent temperature anomaly exceeds H K. It accounts for the magnitude of the day- and night-time temperature anomalies, humidity and wind, as well as for the duration of the heat wave episode. As a preliminary application, we calculated H over a 36 year-long global set of meteorological station data, after a careful quality check procedure. We show that these events, as characterised by H, have doubled in number over the past few decades. We also show that large magnitude heat waves (say H≥8) occur essentially in mid to high latitudes and over continental areas.

  14. Alfven QPOs in magnetars in the anelastic approximation

    CERN Document Server

    Cerdá-Durán, Pablo; Font, José A

    2009-01-01

    We perform two-dimensional simulations of Alfven oscillations in magnetars, modeled as relativistic stars with a dipolar magnetic field. We use the anelastic approximation to general relativistic magnetohydrodynamics, which allows for an effective suppression of fluid modes and an accurate description of Alfven waves. In addition, we compute Alfven oscillation frequencies along individual magnetic field lines with a semi-analytic approach, employing a short-wavelength approximation. Our main findings are as follows: a) we confirm the existence of two families of quasi-periodic oscillations (QPOs), with harmonics at integer multiples of the fundamental frequency, as was found in the linear study of Sotani, Kokkotas & Stergioulas (2008); b) the QPOs appearing near the magnetic axis are split into two groups, depending on their symmetry across the equatorial plane. The antisymmetric QPOs have only odd integer-multiple harmonics; c) the continuum obtained with our semi-analytic approach agrees remarkably well...

  15. Diffusive shock acceleration with magnetic field amplification and Alfvenic drift

    CERN Document Server

    Kang, Hyesung

    2012-01-01

    We explore how wave-particle interactions affect diffusive shock acceleration (DSA) at astrophysical shocks by performing time-dependent kinetic simulations, in which phenomenological models for magnetic field amplification (MFA), Alfvenic drift, thermal leakage injection, Bohm-like diffusion, and a free escape boundary are implemented. If the injection fraction of cosmic-ray (CR) particles is greater than 2x10^{-4}, for the shock parameters relevant for young supernova remnants, DSA is efficient enough to develop a significant shock precursor due to CR feedback, and magnetic field can be amplified up to a factor of 20 via CR streaming instability in the upstream region. If scattering centers drift with Alfven speed in the amplified magnetic field, the CR energy spectrum can be steepened significantly and the acceleration efficiency is reduced. Nonlinear DSA with self-consistent MFA and Alfvenic drift predicts that the postshock CR pressure saturates roughly at 10 % of the shock ram pressure for strong shocks...

  16. Study of heat-stress levels in naturally ventilated sheep barns during heat waves: development and assessment of regression models

    Science.gov (United States)

    Papanastasiou, D. K.; Bartzanas, T.; Panagakis, P.; Zhang, G.; Kittas, C.

    2016-03-01

    It is well documented that heat-stress burdens sheep welfare and productivity. Peak heat-stress levels are observed when high temperatures prevail, i.e. during heat waves; however, continuous measurements inside livestock buildings are not usually available for long periods so as to study the variation of summer heat-stress levels for several years, especially during extreme hot weather. Α methodology to develop a long time series of summer temperature and relative humidity inside naturally ventilated sheep barns is proposed. The accuracy and the transferability of the developed linear regression models were verified. Temperature Humidity Index (THI) was used to assess sheep's potential heat-stress. Τhe variation of THI inside a barn during heat wave and non-heat wave days was examined, and the results were comparatively assessed. The analysis showed that sheep were exposed to moderate, severe, and extreme severe heat-stress in 10, 21 and 66 % of hours, respectively, during heat wave days, while the corresponding values during non-heat wave days were 14, 33 and 43 %, respectively. The heat load on sheep was much higher during heat wave events than during non-heat wave periods. Additionally, based on the averaged diurnal variation of THI, it was concluded that extreme severe heat-stress conditions were prevailing between 1000 and 2400 hours local time during heat wave days. Cool off night periods were never and extremely rarely detected during heat wave and non-heat wave days, respectively.

  17. Spectral Effects on Fast Wave Core Heating and Current Drive

    Energy Technology Data Exchange (ETDEWEB)

    C.K. Phillips, R.E. Bell, L.A. Berry, P.T. Bonoli, R.W. Harvey, J.C. Hosea, E.F. Jaeger, B.P. LeBlanc, P.M. Ryan, G. Taylor, E.J. Valeo, J.R. Wilson, J.C. Wright, H. Yuh, and the NSTX Team

    2009-05-11

    Recent results obtained with high harmonic fast wave (HHFW) heating and current drive (CD) on NSTX strongly support the hypothesis that the onset of perpendicular fast wave propagation right at or very near the launcher is a primary cause for a reduction in core heating efficiency at long wavelengths that is also observed in ICRF heating experiments in numerous tokamaks. A dramatic increase in core heating efficiency was first achieved in NSTX L-mode helium majority plasmas when the onset for perpendicular wave propagation was moved away from the antenna and nearby vessel structures. Efficient core heating in deuterium majority L mode and H mode discharges, in which the edge density is typically higher than in comparable helium majority plasmas, was then accomplished by reducing the edge density in front of the launcher with lithium conditioning and avoiding operational points prone to instabilities. These results indicate that careful tailoring of the edge density profiles in ITER should be considered to limit rf power losses to the antenna and plasma facing materials. Finally, in plasmas with reduced rf power losses in the edge regions, the first direct measurements of high harmonic fast wave current drive were obtained with the motional Stark effect (MSE) diagnostic. The location and radial dependence of HHFW CD measured by MSE are in reasonable agreement with predictions from both full wave and ray tracing simulations.

  18. Plasma Heating by Strong Shock Waves

    International Nuclear Information System (INIS)

    About 104 cm3 of plasma at T ∼ 1 keV, n ∼ 1 x 1016 cm-3, were created by fast collisional shock waves in an electromagnetic shock tube. The speed of these shock waves ranges up to 4 x 108cm/s, corresponding to an acoustic Mach number of 3200 and an Alfvén-Mach number of 15. These experiments were performed in a 3-metre-long coaxial electromagnetic shock tube, employing a 60-μf, 120-kV capacitor bank which produces a 2 x 106 -A drive current. The pre-shock hydrogen initial state was T = 239°K, p = 50 mTorr. The preshock 7.2- kG transverse magnetic field was used to keep the shock thickness small and retard plasma interaction with the walls. Separation of the transverse ionizing shock wave from the driving current was clearly observed, and a hot dense plasma was created behind the shock wave. The state of this plasma was determined by laser interferometer measurements, X-ray bremsstrahlung spectra, a particle energy analyser, probes, and neutron detectors. The shock-created plasma contained an azimuthal magnetic field of B ∼ 22 kG. When deuterium gas was used, neutrons were detected and we estimate a yield of about 5 x 105 neutrons per shot. The transverse ionizing shock thickness, as determined by magnetic field structure, was found to be from 5 to 80 cm thick, the larger values occurring at higher shock speeds. These thicknesses are found to agree with the calculations made from a two-fluid MHD computer code employing classical plasma transport properties. The calculated structure of these collisional shock waves predict that the ion temperature substantially exceeds the electron temperature. (author)

  19. The Impact of Heat Waves on Mortality in Seven Major Cities in Korea

    OpenAIRE

    Son, Ji-Young; Lee, Jong-Tae; Anderson, G. Brooke; Bell, Michelle L.

    2012-01-01

    Background: Understanding the health impacts of heat waves is important, especially given anticipated increases in the frequency, duration, and intensity of heat waves due to climate change. Objectives: We examined mortality from heat waves in seven major Korean cities for 2000 through 2007 and investigated effect modification by individual characteristics and heat wave characteristics (intensity, duration, and timing in season). Methods: Heat waves were defined as ≥ 2 consecutive days with d...

  20. Propagating waves along spicules

    CERN Document Server

    Okamoto, Takenori J

    2011-01-01

    Alfv\\'enic waves are thought to play an important role in coronal heating and acceleration of solar wind. Here we investigated the statistical properties of Alfv\\'enic waves along spicules (jets that protrude into the corona) in a polar coronal hole using high cadence observations of the Solar Optical Telescope (SOT) onboard \\emph{Hinode}. We developed a technique for the automated detection of spicules and high-frequency waves. We detected 89 spicules, and found: (1) a mix of upward propagating, downward propagating, as well as standing waves (occurrence rates of 59%, 21%, and 20%, respectively). (2) The phase speed gradually increases with height. (3) Upward waves dominant at lower altitudes, standing waves at higher altitudes. (4) Standing waves dominant in the early and late phases of each spicule, while upward waves were dominant in the middle phase. (5) In some spicules, we find waves propagating upward (from the bottom) and downward (from the top) to form a standing wave in the middle of the spicule. (...

  1. Particle energization and current sheets in Alfvenic plasma turbulence

    Science.gov (United States)

    Makwana, Kirit; Li, Hui; Guo, Fan; Daughton, William; Cattaneo, Fausto

    2015-11-01

    Plasma turbulence is driven by injecting energy at large scales through stirring or instabilities. This energy cascades forward to smaller scales by nonlinear interactions, described by magnetohydrodynamics (MHD) at scales larger than the ion gyroradius. At smaller scales, the fluid description of MHD breaks down and kinetic mechanisms convert turbulent energy into particle energy. We investigate this entire process by simulating the cascade of strongly interacting Alfven waves using MHD and particle-in-cell (PIC) simulations. The plasma beta is varied and particle heating is analyzed. Anisotropic heating of particles is observed. We calculate the fraction of injected energy converted into non-thermal energy. At low beta we obtain a significant non-thermal component to the particle energy distribution function. We investigate the mechanisms behind this acceleration. The velocity distribution function is correlated with the sites of turbulent current sheets. The different dissipative terms due to curvature drift, gradB drift, polarization drifts, and parallel current density are also calculated. This has applications for understanding particle energization in turbulent space plasmas.

  2. Three-dimensional numerical simulations of fast-to-Alfven conversion in sunspots

    CERN Document Server

    Felipe, T

    2012-01-01

    The conversion of fast waves to the Alfven mode in a realistic sunspot atmosphere is studied through three-dimensional numerical simulations. An upward propagating fast acoustic wave is excited in the high-beta region of the model. The new wave modes generated at the conversion layer are analyzed from the projections of the velocity and magnetic field in their characteristic directions, and the computation of their wave energy and fluxes. The analysis reveals that the maximum efficiency of the conversion to the slow mode is obtained for inclinations of 25 degrees and low azimuths, while the Alfven wave conversions peaks at high inclinations and azimuths between 50 and 120 degrees. Downward propagating Alfven waves appear at the regions of the sunspot where the orientation of the magnetic field is in the direction opposite to the wave propagation, since at these locations the Alfven wave couples better with the downgoing fast magnetic wave which are reflected due to the gradients of the Alfven speed. The simul...

  3. Ionospheric heating with oblique high-frequency waves

    International Nuclear Information System (INIS)

    This paper presents calculations of ionospheric electron temperature and density perturbations and ground-level signal changes produced by intense oblique high-frequency (HF) radio waves. The analysis takes into account focusing at caustics, the consequent Joule heating of the surrounding plasma, heat conduction, diffusion, and recombination processes, these being the effects of a powerful oblique modifying wave. It neglects whatever plasma instabilities might occur. The authors then seek effects on a secondary test wave that is propagated along the same path as the first. The calculations predict ground-level field strength reductions of several decibels in the test wave for modifying waves having effective radiated power (ERP) in the 85- to 90-dBW range. These field strength changes are similar in sign, magnitude, and location to ones measured in Soviet experiments. The location of the signal change is sensitive to the frequency and the model ionosphere assumed; so future experiments should employ the widest possible range of frequencies and propagation conditions. An ERP of 90 dBW seems to be a sort of threshold that, if exceeded, might result in substantial rather than small signal changes. The conclusions are based solely on Joule heating and subsequent refraction of waves passing through caustic regions

  4. A hot topic--heat waves and stroke.

    Science.gov (United States)

    Chan, Fiona; Francis, Oliver; Dodd, Lizzie; Mahdi, Zain; Koblar, Simon A

    2014-10-01

    Following a heat wave in January 2014 in Adelaide, state capital of South Australia, we asked the question whether extreme heat was associated with an increase in stroke incidence. We found in the literature that the association between stroke presentation to hospital and meteorological factors has long been a topic of debate and subject to numerous studies. The literature indicated that an association between heat waves and an increase in admissions for stroke was unlikely in Australia and the United States. We suggest that it may be inappropriate to generalize this conclusion to other countries and rural areas. In view of the global climate change debate, we suggest that prospective studies be focused in developing countries and rural areas to assess the real impact of extreme heat on respective populations to better inform stroke physicians and health policy makers. PMID:25231580

  5. Mesoscale heat waves induced by orography

    Directory of Open Access Journals (Sweden)

    I. Gladich

    2008-07-01

    Full Text Available This work is devoted to the analysis of an unusual and sudden thermal fluctuation that interested portions of Friuli Venezia Giulia (Italy during the night of 27 July 1983. The whole 1983 summer was extremely warm in Europe and in particular on the Italian peninsula, from the Alps down to Sicily. Nevertheless, the day of 27 July 1983 in Friuli Venezia Giulia deserves special attention because the observed maximum temperatures did not occur during day-time but during night-time (from 23:00 up to 24:00 LT, 21:00–22:00 UTC. Peaks of 34.8°C and values of relative humidity of the order of 28% were registered by the official network of weather stations. This event interested mainly the central-eastern part of the plain of Friuli Venezia Giulia, a few kilometers far from the Slovenian border and relieves. The thermal anomalies lasted up to an hour, then temperatures decreased toward values more usual for the climate of the month. The study of this event is carried out with the aid of the AR-WRF numerical atmospheric model, initialized through the ECMWF analysis. The numerical simulations highlight the important role played by orography, jointly with the peculiar thermal structure of the atmosphere, for the enhancing of the internal wave pattern over that area. According to the sensitivity studies realized, the amplification of the internal wave pattern might represent a possible explanation for that meteorological enigma.

  6. Compact star cooling by means of heat waves

    Directory of Open Access Journals (Sweden)

    Nelson Falcón

    2001-01-01

    Full Text Available Compact star cooling theory is revised using the Cattaneo law for the heat flux. It is shown changes in the energy transport equation, insinuates quasiperiodic pulses in the luminosity and predicts that the energy is spread by heat waves changing the cooling time. Applications in rapid variations in single white-dwarf oscillators and quasi periodic luminosity pulses of neutron stars are suggested.

  7. Alfven cyclotron instability and ion cyclotron emission

    International Nuclear Information System (INIS)

    Two-dimensional solutions of compressional Alfven eigenmodes (CAEs) are studied in the cold plasma approximation. For finite inverse aspect ratio tokamak plasmas the two-dimensional eigenmode envelope is localized at the low magnetic field side with the radial and poloidal localization on the order of a/√m and a/4√m, respectively, where m is the dominant poloidal mode number. Charged fusion product driven Alfven cyclotron instability (ACI) of the compressional Alfven eigenmodes provides the explanation for the ion cyclotron emission (ICE) spectrum observed in tokamak experiments. The ACI is excited by fast charged fusion products via Doppler shifted cyclotron wave-particle resonances. The ion cyclotron and electron Landau damping and fast particle instability drive are calculated perturbatively for deuterium-deuterium (DD) and deuterium-tritium (DT) plasmas. Near the plasma edge at the low field side the velocity distribution function of charged fusion products is localized in both pitch angle and velocity. The poloidal localization of the eigenmode enhances the ACI growth rates by a factor of √m in comparison with the previous results without poloidal envelope. The thermal ion cyclotron damping determines that only modes with eigenfrequencies at multiples of the edge cyclotron frequency of the background ions can be easily excited and form an ICE spectrum similar to the experimental observations. Theoretical understanding is given for the results of TFTR DD and DT experiments with υα0/υA ≅ 1 and JET experiments with υα0/υA > 1. (author). 15 refs, 7 figs

  8. Heat conduction analysis of multi-layered FGMs considering the finite heat wave speed

    International Nuclear Information System (INIS)

    Highlights: ► Using a layerwise-incremental differential quadrature for heat transfer of FGMs. ► Superior accuracy with fewer degrees of freedom of the method with respect to FEM. ► Considering multi-layered functionally graded materials. ► Hyperbolic heat transfer analysis of thermal system with heat generation. ► Showing the effect of heat wave speed on thermal characteristic of the system. - Abstract: In this work, the heat conduction with finite wave heat speed of multi-layered domain made of functionally graded materials (FGMs) subjected to heat generation is simulated. For this purpose, the domain is divided into a set of mathematical layers, the number of which can be equal or greater than those of the physical layers. Then, in each mathematical layer, the non-Fourier heat transfer equations are employed. Since, the governing equations have variable coefficients due to FGM properties, as an efficient and accurate method the differential quadrature method (DQM) is adopted to discretize both spatial and temporal domains in each layer. This results in superior accuracy with fewer degrees of freedom than conventional finite element method (FEM). To verify this advantages through some comparison studies, a finite element solution are also obtained. After demonstrating the convergence and accuracy of the method, the effects of heat wave speed for two different set of boundary conditions on the temperature distribution and heat flux of the domain are studied.

  9. The urban heat island dynamics during heat waves: a study of cities in the United States

    Science.gov (United States)

    Hu, Leiqiu

    2016-04-01

    The urban heat island (UHI) is a common phenomenon describing that metropolitan areas are usually warmer than their rural surroundings. This effect is compounded by extreme heat events, which are a leading cause of weather-related human mortality in many countries worldwide. However, the spatial and diurnal variability of temperature and humidity in urban and adjacent rural areas during extreme heat events is not well measured and therefore not well understood. The recently developed dataset of near-surface air and dew temperature from MODIS atmospheric profiles and the new method for the UHI quantification--urban heat island curve are used to quantify the urban climatic changes during heat waves in cities of the United States. The enhanced and weakened UHIs are observed in various cities. The causes of UHI changes during heat waves are discussed, including climate region, vegetation type and amount, city geolocation, etc.

  10. The impact of heat waves on electricity spot markets

    International Nuclear Information System (INIS)

    Thermoelectric power plants depend on cooling water drawn from water bodies. Low river run-off and/or high water temperatures limit a plant's production capacity. This problem may intensify with climate change. Our study quantifies the impact of forced capacity reductions on market prices, production costs, consumer and producer surplus, as well as emissions by means of a bottom-up power generation system model. First, we simulate the German electricity spot market during the heat wave of 2006. Then we conduct a sensitivity study that accounts for future climatic and technological conditions. We find an average price increase of 11% during the heat wave 2006, which is even more pronounced during times of peak demand. Production costs accumulate to an additional but moderate 16 m. Due to the price increase, producers gain from the heat wave, whereas consumers disproportionately bear the costs. Carbon emissions in the German electricity sector increase during the heat wave. The price and cost effects are more pronounced and increase significantly if assumptions on heat-sensitive demand, hydropower capacity, net exports, and capacity reductions are tightened. These are potential additional effects of climate change. Hence, if mitigation fails or is postponed globally, the impacts on the current energy system are very likely to rise. Increases in feed-in from renewable resources and demand-side management can counter the effects to a considerable degree. Countries with a shift toward a renewable energy supply can be expected to be much less susceptible to cooling water scarcity than those with a high share of nuclear and coal-fired power plants. - Highlights: • We quantify the impact of thermal capacity reductions on the electricity market. • German heat wave 2006 caused moderate rise in production costs. • Capacity reductions have substantial impact on prices and raise producer surplus. • Impacts on prices, production cost and surplus amplify under climate

  11. Heat stress related dairy cow mortality during heat waves and control periods in rural Southern Ontario from 2010–2012

    OpenAIRE

    Bishop-Williams, Katherine E.; Berke, Olaf; Pearl, David L.; Hand, Karen; Kelton, David F.

    2015-01-01

    Background Heat stress is a physiological response to extreme environmental heat such as heat waves. Heat stress can result in mortality in dairy cows when extreme heat is both rapidly changing and has a long duration. As a result of climate change, heat waves, which are defined as 3 days of temperatures of 32 °C or above, are an increasingly frequent extreme weather phenomenon in Southern Ontario. Heat waves are increasing the risk for on-farm dairy cow mortality in Southern Ontario. Heat st...

  12. Temperature and heat wave trends in northwest Mexico

    Science.gov (United States)

    Martínez-Austria, Polioptro F.; Bandala, Erick R.; Patiño-Gómez, Carlos

    2016-02-01

    Increase in temperature extremes is one of the main expected impacts of climate change, as well as one of the first signs of its occurrence. Nevertheless, results emerging from General Circulation Models, while sufficient for large scales, are not enough for forecasting local trends and, hence, the IPCC has called for local studies based on on-site data. Indeed, it is expected that climate extremes will be detected much earlier than changes in climate averages. Heat waves are among the most important and least studied climate extremes, however its occurrence has been only barely studied and even its very definition remains controversial. This paper discusses the observed changes in temperature trends and heat waves in Northwestern Mexico, one of the most vulnerable regions of the country. The climate records in two locations of the region are analyzed, including one of the cities with extreme climate in Mexico, Mexicali City in the state of Baja California and the Yaqui River basin at Sonora State using three different methodologies. Results showed clear trends on temperature increase and occurrence of heat waves in both of the study zones using the three methodologies proposed. As result, some policy making suggestion are included in order to increase the adaptability of the studied regions to climate change, particularly related with heat wave occurrence.

  13. Influence of thermal heating on elastic wave velocities in granulite

    Czech Academy of Sciences Publication Activity Database

    Lokajíček, Tomáš; Rudajev, Vladimír; Dwivedi, R.D.; Goel, R. K.; Swarup, A.

    2012-01-01

    Roč. 54, September (2012), s. 1-8. ISSN 1365-1609 R&D Projects: GA AV ČR IAA300130906 Institutional research plan: CEZ:AV0Z30130516 Keywords : thermal heating * P-wave ultrasonic sounding * elastic anisotropy * granulite Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.200, year: 2012

  14. The 2011 marine heat wave in Cockburn Sound, southwest Australia

    Science.gov (United States)

    Rose, T. H.; Smale, D. A.; Botting, G.

    2012-07-01

    Over 2000 km of Western Australian coastline experienced a significant marine heat wave in February and March 2011. Seawater temperature anomalies of +2-4 °C were recorded at a number of locations, and satellite-derived SSTs (sea surface temperatures) were the highest on record. Here, we present seawater temperatures from southwestern Australia and describe, in detail, the marine climatology of Cockburn Sound, a large, multiple-use coastal embayment. We compared temperature and dissolved oxygen levels in 2011 with data from routine monitoring conducted from 2002-2010. A significant warming event, 2-4 °C in magnitude, persisted for > 8 weeks, and seawater temperatures at 10 to 20 m depth were significantly higher than those recorded in the previous 9 yr. Dissolved oxygen levels were depressed at most monitoring sites, being ~ 2 mg l-1 lower than usual in early March 2011. Ecological responses to short-term extreme events are poorly understood, but evidence from elsewhere along the Western Australian coastline suggests that the heat wave was associated with high rates of coral bleaching; fish, invertebrate and macroalgae mortalities; and algal blooms. However, there is a paucity of historical information on ecologically-sensitive habitats and taxa in Cockburn Sound, so that formal examinations of biological responses to the heat wave were not possible. The 2011 heat wave provided insights into conditions that may become more prevalent in Cockburn Sound, and elsewhere, if the intensity and frequency of short-term extreme events increases as predicted.

  15. Responses of tree species to heat waves and extreme heat events.

    Science.gov (United States)

    Teskey, Robert; Wertin, Timothy; Bauweraerts, Ingvar; Ameye, Maarten; McGuire, Mary Anne; Steppe, Kathy

    2015-09-01

    The number and intensity of heat waves has increased, and this trend is likely to continue throughout the 21st century. Often, heat waves are accompanied by drought conditions. It is projected that the global land area experiencing heat waves will double by 2020, and quadruple by 2040. Extreme heat events can impact a wide variety of tree functions. At the leaf level, photosynthesis is reduced, photooxidative stress increases, leaves abscise and the growth rate of remaining leaves decreases. In some species, stomatal conductance increases at high temperatures, which may be a mechanism for leaf cooling. At the whole plant level, heat stress can decrease growth and shift biomass allocation. When drought stress accompanies heat waves, the negative effects of heat stress are exacerbated and can lead to tree mortality. However, some species exhibit remarkable tolerance to thermal stress. Responses include changes that minimize stress on photosynthesis and reductions in dark respiration. Although there have been few studies to date, there is evidence of within-species genetic variation in thermal tolerance, which could be important to exploit in production forestry systems. Understanding the mechanisms of differing tree responses to extreme temperature events may be critically important for understanding how tree species will be affected by climate change. PMID:25065257

  16. Probability of US Heat Waves Affected by a Subseasonal Planetary Wave Pattern

    Science.gov (United States)

    Teng, Haiyan; Branstator, Grant; Wang, Hailan; Meehl, Gerald A.; Washington, Warren M.

    2013-01-01

    Heat waves are thought to result from subseasonal atmospheric variability. Atmospheric phenomena driven by tropical convection, such as the Asian monsoon, have been considered potential sources of predictability on subseasonal timescales. Mid-latitude atmospheric dynamics have been considered too chaotic to allow significant prediction skill of lead times beyond the typical 10-day range of weather forecasts. Here we use a 12,000-year integration of an atmospheric general circulation model to identify a pattern of subseasonal atmospheric variability that can help improve forecast skill for heat waves in the United States. We find that heat waves tend to be preceded by 15-20 days by a pattern of anomalous atmospheric planetary waves with a wavenumber of 5. This circulation pattern can arise as a result of internal atmospheric dynamics and is not necessarily linked to tropical heating.We conclude that some mid-latitude circulation anomalies that increase the probability of heat waves are predictable beyond the typical weather forecast range.

  17. On the construction of heat wave in symmetric case

    Science.gov (United States)

    Kazakov, A. L.; Lempert, A. A.

    2016-06-01

    A nonlinear second-order parabolic equation with two variables is considered. Under additional conditions, this equation can be interpreted as the porous medium equation in case of dependence of the unknown function on two variables: time and distance from the origin. The equation has a wide variety of applications in continuum mechanics, for example, it is applicable for mathematical modeling of filtration of ideal polytropic gas in porous media or heat conduction. The authors deal with a special solutions which are usually called heat waves. A special feature of such solution is that it consists of two continuously joined solutions. The first of them is trivial and the second one is nonnegative. The heat wave solution can have discontinuous derivatives on the line of joint which is called the front of heat wave, i.e. smoothness of the solution, generally speaking, is broken. The most natural problem which has such solutions is the so-called “the Sakharov problem of the initiation of a heat wave”. New solutions of the problem in the form of multiple power series for physical variables are constructed. The coefficients of the series are obtained from tridiagonal systems of linear algebraic equations. Herewith, the elements of matrices of this systems depend on the matrix order and the condition of the diagonal dominance is not fulfilled. The recurrent formulas for the coefficients are suggested.

  18. Bulk ion heating with ICRF waves in tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Mantsinen, M. J., E-mail: mervi.mantsinen@bsc.es [Catalan Institution for Research and Advanced Studies, Barcelona (Spain); Barcelona Supercomputing Center, Barcelona (Spain); Bilato, R.; Bobkov, V. V.; Kappatou, A.; McDermott, R. M.; Odstrčil, T.; Tardini, G.; Bernert, M.; Dux, R.; Maraschek, M.; Noterdaeme, J.-M.; Ryter, F.; Stober, J. [Max-Planck-Institut für Plasmaphysik, Garching (Germany); Nocente, M. [Dipartimento di Fisica “G. Occhialini”, Università degli Studi di Milano-Bicocca, Milano (Italy); Istituto di Fisica del Plasma “P. Caldirola”, CNR, Milano (Italy); Hellsten, T. [Dept. of Fusion Plasma Physics, EES, KTH, Stockholm (Sweden); Mantica, P.; Tardocchi, M. [Istituto di Fisica del Plasma “P. Caldirola”, CNR, Milano (Italy); Nielsen, S. K.; Rasmussen, J.; Stejner, M. [Technical University of Denmark, Department of Physics, Lyngby (Denmark); and others

    2015-12-10

    Heating with ICRF waves is a well-established method on present-day tokamaks and one of the heating systems foreseen for ITER. However, further work is still needed to test and optimize its performance in fusion devices with metallic high-Z plasma facing components (PFCs) in preparation of ITER and DEMO operation. This is of particular importance for the bulk ion heating capabilities of ICRF waves. Efficient bulk ion heating with the standard ITER ICRF scheme, i.e. the second harmonic heating of tritium with or without {sup 3}He minority, was demonstrated in experiments carried out in deuterium-tritium plasmas on JET and TFTR and is confirmed by ICRF modelling. This paper focuses on recent experiments with {sup 3}He minority heating for bulk ion heating on the ASDEX Upgrade (AUG) tokamak with ITER-relevant all-tungsten PFCs. An increase of 80% in the central ion temperature T{sub i} from 3 to 5.5 keV was achieved when 3 MW of ICRF power tuned to the central {sup 3}He ion cyclotron resonance was added to 4.5 MW of deuterium NBI. The radial gradient of the T{sub i} profile reached locally values up to about 50 keV/m and the normalized logarithmic ion temperature gradients R/LT{sub i} of about 20, which are unusually large for AUG plasmas. The large changes in the T{sub i} profiles were accompanied by significant changes in measured plasma toroidal rotation, plasma impurity profiles and MHD activity, which indicate concomitant changes in plasma properties with the application of ICRF waves. When the {sup 3}He concentration was increased above the optimum range for bulk ion heating, a weaker peaking of the ion temperature profile was observed, in line with theoretical expectations.

  19. Aerodynamic Heating in Hypersonic Boundary Layers:\\ Role of Dilatational Waves

    CERN Document Server

    Zhu, Yiding; Wu, Jiezhi; Chen, Shiyi; Lee, Cunbiao; Gad-el-Hak, Mohamed

    2016-01-01

    The evolution of multi-mode instabilities in a hypersonic boundary layer and their effects on aerodynamic heating are investigated. Experiments are conducted in a Mach 6 wind tunnel using Rayleigh-scattering flow visualization, fast-response pressure sensors, fluorescent temperature-sensitive paint (TSP), and particle image velocimetry (PIV). Calculations are also performed based on both parabolized stability equations (PSE) and direct numerical simulations (DNS). It is found that second-mode dilatational waves, accompanied by high-frequency alternating fluid compression and expansion, produce intense aerodynamic heating in a small region that rapidly heats the fluid passing through it. As a result, the surface temperature rapidly increases and results in an overshoot over the nominal transitional value. When the dilatation waves decay downstream, the surface temperature decreases gradually until transition is completed. A theoretical analysis is provided to interpret the temperature distribution affected by ...

  20. Mortality during heat waves in South Korea, 1991 to 2005: How exceptional was the 1994 heat wave?

    Czech Academy of Sciences Publication Activity Database

    Kyselý, Jan; Kim, J.

    2009-01-01

    Roč. 38, č. 2 (2009), s. 105-116. ISSN 0936-577X R&D Projects: GA ČR GC205/07/J044 Institutional research plan: CEZ:AV0Z30420517 Keywords : heat wave * human mortality * East Asia * extreme events * climate change Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 2.250, year: 2009

  1. Closed Field Coronal Heating Models Inspired by Wave Turbulence

    Science.gov (United States)

    Downs, C.; Lionello, R.; Mikic, Z.; Linker, J.; Velli, M. M.

    2013-12-01

    To simulate the energy balance of coronal plasmas on macroscopic scales, we often require the specification of the coronal heating mechanism in some functional form. To go beyond empirical formulations and to build a more physically motivated heating function, we investigate the wave-turbulence dissipation (WTD) phenomenology for the heating of closed coronal loops. To do so, we employ an implementation of non-WKB equations designed to capture the large-scale propagation, reflection, and dissipation of wave turbulence along a loop. The parameter space of this model is explored by solving the coupled WTD and hydrodynamic equations in 1D for an idealized loop, and the relevance to a range of solar conditions is established by computing solutions for several hundred loops extracted from a realistic 3D coronal field. Due to the implicit dependence of the WTD heating model on loop geometry and plasma properties along the loop and at the footpoints, we find that this model can significantly reduce the number of free parameters when compared to traditional empirical heating models, and still robustly describe a broad range of quiet-sun and active region conditions. The importance of the self-reflection term in producing realistic heating scale heights and thermal non-equilibrium cycles is discussed, and preliminary 3D thermodynamic MHD simulations using this formulation are presented. Research supported by NASA and NSF.

  2. Supersonic Propagation of Heat Waves in Low Density Heavy Material

    Institute of Scientific and Technical Information of China (English)

    Jiang Shaoen; Zhang Wenhai; Yi Rongqing; Cui Yanli; Chen Jiusen; Xu Yan; Ding Yongkun; Lai Dongxian; Zheng Zhijian; Huang Yikiang; Li Jinghong; Sun Kexu; Hu Xin

    2005-01-01

    The propagation of a supersonic heat-wave through copper-doped foam with a density of 50 mg/cm3 was experimentally investigated. The wave is driven by 140 eV Holhraum radiations generated in a cylindrical gold cavity heated by a 2 k J, 1ns laser pulse (0.35 μm). The delayed breakout time of the radiation waves from the rear side of the foam is measured by a threechromatic streaked x-ray spectrometer (TCS) consisting of a set of three-imaging pinholes and an array of three transmission gratings coupled with an x-ray streak camera (XSC). With one shot,simultaneous measurements of the delays of the drive source and the radiation with two different energies (210 eV, 840 eV) through the foam have been made for the first time. The experimental results indicate that the time delays vary with photon energies. The radiation with an energy of 210 eV propagates at a lower velocity. The radiating heat wave propagates with a velocity that is larger than the sound speed. Using TGS, the transmitting spectrum was measured, and then lower limit of the optical depth which is more than 1, was obtained. The experimental data were in agreement with numerical simulations.

  3. Lower hybrid wave heating into neutral beam heated plasma in the JT-60 tokamak

    International Nuclear Information System (INIS)

    Injection of high-power lower hybrid waves (LHW) of up to 6.0 MW into neutral-beam-20 MW-heated plasmas with the medium electron density regime (n-bare ≤ 3.5 x 1019 m-3) increases the plasma energy content at the same incremental energy confinement time as in the case of neutral beam heating alone. In addition to thermal electron and ion heating, LHW accelerates beam ions to energies considerably higher than the beam injection energy. In contrast to LH injection into OH plasmas in the same density regime, where substantial high-energy electron production is observed, the case of combined heating shows much less high-energy electrons. The heating efficiency of LHW in the combined heating case tends to decrease as the electron density is increased. Ray-tracing analysis suggests that the accessibility condition prevents effective heating in a high-density plasma. Estimation of wave damping, which is taking account of the beam component of the ion velocity distribution function, indicates that waves are absorbed by beam ions before they are absorbed by electrons. (author)

  4. Alfvenic Turbulence from the Sun to 65 Solar Radii: Numerical predictions.

    Science.gov (United States)

    Perez, J. C.; Chandran, B. D. G.

    2015-12-01

    The upcoming NASA Solar Probe Plus (SPP) mission will fly to within 9 solar radii from the solar surface, about 7 times closer to the Sun than any previous spacecraft has ever reached. This historic mission will gather unprecedented remote-sensing data and the first in-situ measurements of the plasma in the solar atmosphere, which will revolutionize our knowledge and understanding of turbulence and other processes that heat the solar corona and accelerate the solar wind. This close to the Sun the background solar-wind properties are highly inhomogeneous. As a result, outward-propagating Alfven waves (AWs) arising from the random motions of the photospheric magnetic-field footpoints undergo strong non-WKB reflections and trigger a vigorous turbulent cascade. In this talk I will discuss recent progress in the understanding of reflection-driven Alfven turbulence in this scenario by means of high-resolution numerical simulations, with the goal of predicting the detailed nature of the velocity and magnetic field fluctuations that the SPP mission will measure. In particular, I will place special emphasis on relating the simulations to relevant physical mechanisms that might govern the radial evolution of the turbulence spectra of outward/inward-propagating fluctuations and discuss the conditions that lead to universal power-laws.

  5. Gravitational Wave Heating of Stars and Accretion Disks

    CERN Document Server

    Li, Gongjie; Loeb, Abraham

    2012-01-01

    We investigate the electromagnetic (EM) counterpart of gravitational waves (GWs) emitted by a supermassive black hole binary (SMBHB) through the viscous dissipation of the GW energy in an accretion disk and stars surrounding the SMBHB. We account for the suppression of the heating rate if the forcing period is shorter than the turnover time of the largest turbulent eddies. We find that the viscous heating luminosity in 0.1 solar mass stars can be significantly higher than their intrinsic luminosity. The relative brightening is small for accretion disks.

  6. The Impact of the Urban Heat Island during an Intense Heat Wave in Oklahoma City

    Directory of Open Access Journals (Sweden)

    Jeffrey B. Basara

    2010-01-01

    Full Text Available During late July and early August 2008, an intense heat wave occurred in Oklahoma City. To quantify the impact of the urban heat island (UHI in Oklahoma City on observed and apparent temperature conditions during the heat wave event, this study used observations from 46 locations in and around Oklahoma City. The methodology utilized composite values of atmospheric conditions for three primary categories defined by population and general land use: rural, suburban, and urban. The results of the analyses demonstrated that a consistent UHI existed during the study period whereby the composite temperature values within the urban core were approximately 0.5∘C warmer during the day than the rural areas and over 2∘C warmer at night. Further, when the warmer temperatures were combined with ambient humidity conditions, the composite values consistently revealed even warmer heat-related variables within the urban environment as compared with the rural zone.

  7. Heat wave fast ignition in inertial confinement energy

    Institute of Scientific and Technical Information of China (English)

    Shalom; Eliezer; Shirly; Vinikman; Pinhasi

    2013-01-01

    An accelerated micro-foil is used to ignite a pre-compressed cylindrical shell containing deuterium–tritium fuel.The well-known shock wave ignition criterion and a novel criterion based on heat wave ignition are developed in this work.It is shown that for heat ignition very high impact velocities are required.It is suggested that a multi-petawatt laser can accelerate a micro-foil to relativistic velocities in a very short time duration(picosecond)of the laser pulse.The cylindrical geometry suggested here for the fast ignition approach has the advantage of geometrically separating the nanosecond lasers that compress the target from the picosecond laser that accelerates the foil.The present model suggests that nuclear fusion by micro-foil impact ignition could be attained with currently existing technology.

  8. Attractors of magnetohydrodynamic flows in an Alfvenic state

    Energy Technology Data Exchange (ETDEWEB)

    Nunez, Manuel; Sanz, Javier [Departamento de Analisis Matematico, Universidad de Valladolid, Valladolid (Spain)

    1999-08-13

    We present a simplified form of the magnetohydrodynamic system which describes the evolution of a plasma where the small-scale velocity and magnetic field are aligned in the form of Alfven waves, such as happens in several turbulent situations. Bounds on the dimension of the global attractor are found, and are shown to be an improvement of the standard ones for the full magnetohydrodynamic equations. (author)

  9. Tropical Gravity Wave Momentum Fluxes and Latent Heating Distributions

    Science.gov (United States)

    Geller, Marvin A.; Zhou, Tiehan; Love, Peter T.

    2015-01-01

    Recent satellite determinations of global distributions of absolute gravity wave (GW) momentum fluxes in the lower stratosphere show maxima over the summer subtropical continents and little evidence of GW momentum fluxes associated with the intertropical convergence zone (ITCZ). This seems to be at odds with parameterizations forGWmomentum fluxes, where the source is a function of latent heating rates, which are largest in the region of the ITCZ in terms of monthly averages. The authors have examined global distributions of atmospheric latent heating, cloud-top-pressure altitudes, and lower-stratosphere absolute GW momentum fluxes and have found that monthly averages of the lower-stratosphere GW momentum fluxes more closely resemble the monthly mean cloud-top altitudes rather than the monthly mean rates of latent heating. These regions of highest cloud-top altitudes occur when rates of latent heating are largest on the time scale of cloud growth. This, plus previously published studies, suggests that convective sources for stratospheric GW momentum fluxes, being a function of the rate of latent heating, will require either a climate model to correctly model this rate of latent heating or some ad hoc adjustments to account for shortcomings in a climate model's land-sea differences in convective latent heating.

  10. Multivariate Statistical Modelling of Drought and Heat Wave Events

    Science.gov (United States)

    Manning, Colin; Widmann, Martin; Vrac, Mathieu; Maraun, Douglas; Bevaqua, Emanuele

    2016-04-01

    Multivariate Statistical Modelling of Drought and Heat Wave Events C. Manning1,2, M. Widmann1, M. Vrac2, D. Maraun3, E. Bevaqua2,3 1. School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK 2. Laboratoire des Sciences du Climat et de l'Environnement, (LSCE-IPSL), Centre d'Etudes de Saclay, Gif-sur-Yvette, France 3. Wegener Center for Climate and Global Change, University of Graz, Brandhofgasse 5, 8010 Graz, Austria Compound extreme events are a combination of two or more contributing events which in themselves may not be extreme but through their joint occurrence produce an extreme impact. Compound events are noted in the latest IPCC report as an important type of extreme event that have been given little attention so far. As part of the CE:LLO project (Compound Events: muLtivariate statisticaL mOdelling) we are developing a multivariate statistical model to gain an understanding of the dependence structure of certain compound events. One focus of this project is on the interaction between drought and heat wave events. Soil moisture has both a local and non-local effect on the occurrence of heat waves where it strongly controls the latent heat flux affecting the transfer of sensible heat to the atmosphere. These processes can create a feedback whereby a heat wave maybe amplified or suppressed by the soil moisture preconditioning, and vice versa, the heat wave may in turn have an effect on soil conditions. An aim of this project is to capture this dependence in order to correctly describe the joint probabilities of these conditions and the resulting probability of their compound impact. We will show an application of Pair Copula Constructions (PCCs) to study the aforementioned compound event. PCCs allow in theory for the formulation of multivariate dependence structures in any dimension where the PCC is a decomposition of a multivariate distribution into a product of bivariate components modelled using copulas. A

  11. Impacts of Summer 2003 Heat Wave in Europe

    OpenAIRE

    De Bono, Andréa; Peduzzi, Pascal; Kluser, Stéphane; Giuliani, Gregory

    2004-01-01

    The extreme drought and heat wave that hit Europe in the summer of 2003 had enormous adverse social, economic and environmental effects, such as the death of thousands of vulnerable elderly people, the destruction of large areas of forests by fire, and effects on water ecosystems and glaciers. It caused power cuts and transport restrictions and a decreased agricultural production. The losses are estimated to exceed 13 billion euros.

  12. The 2011 marine heat wave off southwest Australia

    OpenAIRE

    T. H. Rose; D. A. Smale; G. Botting

    2012-01-01

    Over 2000 km of Western Australian coastline experienced a significant marine heat wave in February and March 2011. Seawater temperature anomalies of +2–4 °C were recorded at a number of locations and satellite-derived SSTs were the highest on record. Here, we present seawater temperatures from southwestern Australia and describe, in detail, the marine climatology of Cockburn Sound; a large, multiple-use coastal embayment. We compared temperature and dissolved oxygen levels in 2011 with data ...

  13. The 2011 marine heat wave in Cockburn Sound, southwest Australia

    OpenAIRE

    T. H. Rose; D. A. Smale; G. Botting

    2012-01-01

    Over 2000 km of Western Australian coastline experienced a significant marine heat wave in February and March 2011. Seawater temperature anomalies of +2–4 °C were recorded at a number of locations, and satellite-derived SSTs (sea surface temperatures) were the highest on record. Here, we present seawater temperatures from southwestern Australia and describe, in detail, the marine climatology of Cockburn Sound, a large, multiple-use coastal embayment. We compared temperature and dissolved oxyg...

  14. The 2011 marine heat wave in Cockburn Sound, southwest Australia

    Directory of Open Access Journals (Sweden)

    T. H. Rose

    2012-07-01

    Full Text Available Over 2000 km of Western Australian coastline experienced a significant marine heat wave in February and March 2011. Seawater temperature anomalies of +2–4 °C were recorded at a number of locations, and satellite-derived SSTs (sea surface temperatures were the highest on record. Here, we present seawater temperatures from southwestern Australia and describe, in detail, the marine climatology of Cockburn Sound, a large, multiple-use coastal embayment. We compared temperature and dissolved oxygen levels in 2011 with data from routine monitoring conducted from 2002–2010. A significant warming event, 2–4 °C in magnitude, persisted for > 8 weeks, and seawater temperatures at 10 to 20 m depth were significantly higher than those recorded in the previous 9 yr. Dissolved oxygen levels were depressed at most monitoring sites, being ~ 2 mg l−1 lower than usual in early March 2011. Ecological responses to short-term extreme events are poorly understood, but evidence from elsewhere along the Western Australian coastline suggests that the heat wave was associated with high rates of coral bleaching; fish, invertebrate and macroalgae mortalities; and algal blooms. However, there is a paucity of historical information on ecologically-sensitive habitats and taxa in Cockburn Sound, so that formal examinations of biological responses to the heat wave were not possible. The 2011 heat wave provided insights into conditions that may become more prevalent in Cockburn Sound, and elsewhere, if the intensity and frequency of short-term extreme events increases as predicted.

  15. The 2011 marine heat wave off southwest Australia

    Directory of Open Access Journals (Sweden)

    T. H. Rose

    2012-04-01

    Full Text Available Over 2000 km of Western Australian coastline experienced a significant marine heat wave in February and March 2011. Seawater temperature anomalies of +2–4 °C were recorded at a number of locations and satellite-derived SSTs were the highest on record. Here, we present seawater temperatures from southwestern Australia and describe, in detail, the marine climatology of Cockburn Sound; a large, multiple-use coastal embayment. We compared temperature and dissolved oxygen levels in 2011 with data from routine monitoring conducted from 2002–2010. A significant warming event, 2–4 °C in magnitude, persisted for >8 weeks, and seawater temperatures at 10 to 20 m depth were significantly higher than those recorded in the previous 9 yr. Dissolved oxygen levels were depressed at most monitoring sites, being ~2 mg l−1 lower than usual in early March 2011. Ecological responses to short-term extreme events are poorly understood, but evidence from elsewhere along the Western Australian coastline suggests that the heat wave was associated with high rates of coral bleaching, fish, invertebrate and macroalgae mortalities, and algal blooms. However, more ecological information from Cockburn Sound and other multiple-use embayments is urgently needed. The 2011 heat wave provided insights into conditions that may become more prevalent in Cockburn Sound, and elsewhere, if the intensity and frequency of short-term extreme events increases as predicted.

  16. The 2011 marine heat wave off southwest Australia

    Science.gov (United States)

    Rose, T. H.; Smale, D. A.; Botting, G.

    2012-04-01

    Over 2000 km of Western Australian coastline experienced a significant marine heat wave in February and March 2011. Seawater temperature anomalies of +2-4 °C were recorded at a number of locations and satellite-derived SSTs were the highest on record. Here, we present seawater temperatures from southwestern Australia and describe, in detail, the marine climatology of Cockburn Sound; a large, multiple-use coastal embayment. We compared temperature and dissolved oxygen levels in 2011 with data from routine monitoring conducted from 2002-2010. A significant warming event, 2-4 °C in magnitude, persisted for >8 weeks, and seawater temperatures at 10 to 20 m depth were significantly higher than those recorded in the previous 9 yr. Dissolved oxygen levels were depressed at most monitoring sites, being ~2 mg l-1 lower than usual in early March 2011. Ecological responses to short-term extreme events are poorly understood, but evidence from elsewhere along the Western Australian coastline suggests that the heat wave was associated with high rates of coral bleaching, fish, invertebrate and macroalgae mortalities, and algal blooms. However, more ecological information from Cockburn Sound and other multiple-use embayments is urgently needed. The 2011 heat wave provided insights into conditions that may become more prevalent in Cockburn Sound, and elsewhere, if the intensity and frequency of short-term extreme events increases as predicted.

  17. Heat Waves: The Intersection of Climate and Public Health

    Science.gov (United States)

    Schindler, J. V.; Grant, F.

    2011-12-01

    Heat waves are deadly weather-related exposures in the U.S. and account for more deaths annually than hurricanes, tornadoes, floods, and earthquakes combined. From a public health perspective, all morbidity and mortality associated with extreme heat events are completely preventable. Related environmental events that can impact health-poor air quality, concentrations of greenhouse gases, and the inability to cool at night-are all expected to increase in severity and frequency over this next century. Northrop Grumman's active program of climate science combines inputs from public health, population health analytics, advanced agent-based modeling and simulation, and high performance computing to assist the characterization of how climate change impacts human health in specific geographies. In this study, we defined heat waves as 3+ consecutive days when the high temperature is 10+ degrees (Fahrenheit) higher than the mean summer high temperature. To address current deficiencies in local planning and decision making with respect to regional climate change and its effect on human health, our research focused on performing a dynamical downscaling with the Weather Research and Forecasting (WRF) model to develop decision aids that translate the regional climate data into actionable information for users. WRF was run in nested mode at spatial resolution of 108 km, 36 km and 12 km and 28 vertical levels. We used WRF simulated temperatures at 2 meters above the surface to calculate the annual average number of days spent in heat waves. Our results indicated a significant increase in heat wave episodes-a direct consequence of steadily increasing maximum temperatures in the future. Our discussion continues with clarification of how public health must become integral to future community, civic, healthcare, and emergency preparedness planning. While continued growth in the number of persons living in urban areas will result in increased exposure to heat-related health risks

  18. Study of the effect of compressional Alfven modes on thermal transport in the National Spherical Torus Experiment

    International Nuclear Information System (INIS)

    With the first injection of neutral beams into the National Spherical Torus Experiment (NSTX) [Ono et al., Nucl. Fusion 40, 557 (2000)], a broad spectrum of fluctuations consisting of nearly equally spaced peaks in the frequency range from about 0.2 to 1.2 times the ion cyclotron frequency was observed. The frequencies scale with toroidal field and plasma density consistently with Alfven waves. From these and other observations, the modes have been identified as compressional Alfven eigenmodes (CAE). It has also recently been found that the ratio of the measured ion and electron temperatures in NSTX during neutral beam heating is anomalously high [Bell, Bull. Am. Phys. Soc. 46, 206 (2001)]. To explain the anomaly in the ratio of ion to electron temperature, it has been suggested that the CAE, driven by the beam ions, stochastically heat the thermal ions [Gates et al., Phys. Rev. Lett. 87, 205003 (2001)]. In this paper it is shown through studies of the power balance that stochastic heating of the thermal ions by the observed CAE alone is not solely responsible for the anomaly in the ion to electron temperature ratio

  19. Plasma heating via electron Bernstein wave heating using ordinary and extraodinary mode

    Directory of Open Access Journals (Sweden)

    A. Parvazian

    2008-03-01

    Full Text Available Magnetically confined plasma can be heated with high power microwave sources. In spherical torus the electron plasma frequency exeeds the electron cyclotron frequency (EC and, as a consequence, electromagnetic waves at fundamental and low harmonic EC cannot propagate within the plasma. In contrast, electron Bernstein waves (EBWs readily propagate in spherical torus plasma and are absorbed strongly at the electron cyclotron resonances. In order to proagate EBWs beyond the upper hybrid resonance (UHR, that surrounds the plasma, the EBWs must convert via one of two processes to either ordinary (O-mode or extraordinary (X-mode electromagnetic waves. O-mode and X-mode electromagnetic waves lunched at the plasma edge can convert to the electron Bernstein waves (EBWs which can propagate without and cut-off into the core of the plasma and damp on electrons. Since the electron Bernstein wave (EBW has no cut-off limits, it is well suited to heat an over-dense plasma by resonant absorption. An important problem is to calculate mode conversion coefficient that is very sensitive to density. Mode conversion coefficient depends on Budden parameter ( ñ and density scale length (Ln in upper hybrid resonance (UHR. In Mega Ampere Spherical Tokamak (MAST, the optimized conversion efficiency approached 72.5% when Ln was 4.94 cm and the magnetic field was 0.475 Tesla in the core of the plasma.

  20. Acceleration of Alfven solitons

    International Nuclear Information System (INIS)

    We study the dynamics of solitons perturbed by an external harmonic driver. These are described by a derivative nonlinear Schroedinger equation (DNLSE) which we solve by pseudo-spectral simulations over a 1024 point grid. Under the action of the perturbation, low-amplitude non-linearly interacting wave modes develop, which eventually degenerate into chaotic oscillations characterized by a positive maximum Lyapunov exponent and a large dimension. After this stage (which lasts about 10 driver's periods), an initially injected soliton (the initial condition) sets down to a train of pulse-shaped structures. These pulses have all the same speed and move in the same direction of the original soliton, retaining its polarization. However, the number of pulses in the numerical box and the time interval between them point out a translation speed which is about 4 times the one of the original soliton; the amplitude and width of the pulses are respectively about 2 and 1/4 times the ones of the original soliton. This suggests that the observed structure is itself a soliton which in fact solves the DNLSE. In other words, it appears as if the DNLSE nonlinearly stored the energy intake out of the driver into more energetic, faster and narrower solitons, a phenomenon we refer to as soliton acceleration. In the meanwhile, the above reported chaotic oscillations have entered an energy-cascade regime, and they have generated a low-level turbulent background in which the solitary structure is embedded. These features are spectrally analyzed to produce power-law wave-number and frequency spectra. An inertial range exists where the spectral indexes are about -1.45 and -1.5 for the wave-number and the frequency spectrum respectively. (orig.)

  1. An approach to quantify the heat wave strength and price a heat derivative for risk hedging

    Science.gov (United States)

    Shen, Samuel S. P.; Kramps, Benedikt; Sun, Shirley X.; Bailey, Barbara

    2012-01-01

    Mitigating the heat stress via a derivative policy is a vital financial option for agricultural producers and other business sectors to strategically adapt to the climate change scenario. This study has provided an approach to identifying heat stress events and pricing the heat stress weather derivative due to persistent days of high surface air temperature (SAT). Cooling degree days (CDD) are used as the weather index for trade. In this study, a call-option model was used as an example for calculating the price of the index. Two heat stress indices were developed to describe the severity and physical impact of heat waves. The daily Global Historical Climatology Network (GHCN-D) SAT data from 1901 to 2007 from the southern California, USA, were used. A major California heat wave that occurred 20-25 October 1965 was studied. The derivative price was calculated based on the call-option model for both long-term station data and the interpolated grid point data at a regular 0.1°×0.1° latitude-longitude grid. The resulting comparison indicates that (a) the interpolated data can be used as reliable proxy to price the CDD and (b) a normal distribution model cannot always be used to reliably calculate the CDD price. In conclusion, the data, models, and procedures described in this study have potential application in hedging agricultural and other risks.

  2. An Approach to Quantify the Heat Wave Strength and Price a Heat Derivative for Risk Hedging

    Institute of Scientific and Technical Information of China (English)

    Samuel S. P. SHEN; Benedikt KRAMPS; Shirley X. SUN; Barbara BAILEY

    2012-01-01

    Mitigating the heat stress via a derivative policy is a vital financial option for agricultural producers and other business sectors to strategically adapt to the climate change scenario.This study has provided an approach to identifying heat stress events and pricing the heat stress weather derivative due to persistent days of high surface air temperature (SAT).Cooling degree days (CDD) are used as the weather index for trade.In this study,a call-option model was used as an example for calculating the price of the index.Two heat stress indices were developed to describe the severity and physical impact of heat waves.The daily Global Historical Climatology Network (GHCN-D) SAT data from 1901 to 2007 from the southern California,USA,were used.A major California heat wave that occurred 20-25 October 1965 was studied.The derivative price was calculated based on the call-option model for both long-term station data and the interpolated grid point data at a regular 0.1°×0.1° latitude-longitude grid.The resulting comparison indicates that (a) the interpolated data can be used as reliable proxy to price the CDD and (b) a normal distribution model cannot always be used to reliably calculate the CDD price.In conclusion,the data,models,and procedures described in this study have potential application in hedging agricultural and other risks.

  3. Linear wave propagation in a hot axisymmetric toroidal plasma

    International Nuclear Information System (INIS)

    Kinetic effects on the propagation of the Alfven wave are studied for the first time in a toroidal plasma relevant for experiments. This requires the resolution of a set of coupled partial differential equations whose coefficients depend locally on the plasma parameters. For this purpose, a numerical wave propagation code called PENN has been developed using either a bilinear or a bicubic Hermite finite element discretization. It solves Maxwell's equations in toroidal geometry, with a dielectric tensor operator that takes into account the linear response of the plasma. Two different models have been implemented and can be used comparatively to describe the same physical case: the first treats the plasma as resistive fluids and gives results which are in good agreement with toroidal fluid codes. The second is a kinetic model and takes into account the finite size of the Larmor radii; it has successfully been tested against a kinetic plasma model in cylindrical geometry. New results have been obtained when studying kinetic effects in toroidal geometry. Two different conversion mechanisms to the kinetic Alfven wave have been described: one occurs at toroidally coupled resonant surfaces and is the kinetic counterpart of the fluid models' resonance absorption. The other has no such correspondence and results directly from the toroidal coupling between the kinetic Alfven wave and the global wavefield. An analysis of a heating scenario suggests that it might be difficult to heat a plasma with Alfven waves up to temperatures that are relevant for a tokamak reactor. Kinetic effects are studied for three types of global Alfven modes (GAE, TAE, BAE) and a new class of kinetic eigenmodes is described which appear inside the fluid gap: it could be related to recent observations in the JET (Joint European Torus) tokamak. (author) 56 figs., 6 tabs., 58 refs

  4. Wave heating of an ion beam in a tokamak plasma

    International Nuclear Information System (INIS)

    Heating of a 26-keV trapped-ion beam by interaction with incident lower-hybrid RF power (as low as 5kW) was observed in the ATC plasma. We suggest that ion-cyclotron damping of lower hybrid waves by beam ions can account for the increase in beam energy. This process can explain the main features of the experiment: (1) preferential absorption in the perpendicular direction, (2) lack of absorption by the background plasma ions, and (3) low power requirement for absorption. Theory requires ksub(perpendicular)rhosub(i) approximately > (ω/ωsub(ci))sup(1/2). The relatively high perpendicular temperature of the beam ions (approximately 1keV), combined with one of several possibilities for RF energy at large ksub(perpendicular), allows the condition on ksub(perpendicular)rhosub(i) to be satisfied. Moreover, the large parallel energy of the beam ions plays a major role in broadening the harmonic resonances, thus making it possible for a large number of beam ions to resonate with the wave. Though the primary process is perpendicular absorption, there is also a net gain in parallel energy during a collision time due to pitch-angle scattering. The importance of this heating mechanism for large machines such as TFTR is discussed. For these machines, ions will be injected with large rhosub(i), making ion heating possible even with moderate values of ksub(perpendicular). (author)

  5. Ion Bernstein wave heating experiments on PBX-M

    International Nuclear Information System (INIS)

    A multi-megawatt level IBWH experiment on PBX-M1 is in preparation. The goal of the expriment is to contribute to the attainment of the high beta, second regime of stability. The high power IBWH will be used as an additional heating power source to supplement the existing 6 MW of NBI power to achieve higher β values in PBX-M. Bulk ion heating via IBW excitation with localized, off-axis deposition can be used to modify the pressure profile for improved plasma stability at high β. The high power off-axis heating in principle can generate a significant boostrap current 2(∼30%) in the outer region of the PBX-M plasma complementing LHCD for broadening the current profiles. It is also interesting to note that the available rf power (∼4 MW) is comparable to the predicted power levels required for the rf ponderomotive stabilization of pressure driven modes (such as the high-n ballooning3 and external kink modes4) for the closely fitted stabilizing shell configuration of PBX-M. There are, however, several experimental factors that require careful consideration in planning a high power experiment. Four important factors are discussed here in some detail: 1. Antenna location. 2. Effects of parallel electric fields. 3. Modification of launched wave spectrum due to antenna misalignement 4. Possible interference of wave launching by protective limiters

  6. Could aerosol emissions be used for regional heat wave mitigation?

    Directory of Open Access Journals (Sweden)

    D. N. Bernstein

    2013-07-01

    Full Text Available Geoengineering applications by injection of sulfate aerosols into the stratosphere are under consideration as a measure of last resort to counter global warming. Here a potential regional-scale application to offset the impacts of heat waves is critically examined. Using the Weather Research and Forecasting model with fully coupled chemistry (WRF-Chem, the effect of regional-scale sulfate aerosol emission over California in each of two days of the July 2006 heat wave is used to quantify potential reductions in surface temperature as a function of emission rates in a layer at 12 km altitude. Local meteorological factors yield geographical differences in surface air temperature sensitivity. For emission rates of approximately 30 μg m−2 s−1 of sulfate aerosols (with standard WRF-Chem size distribution over the region, temperature decreases of around 7 °C result during the middle part of the day over the Central Valley, one of the areas hardest hit by the heat wave. Regions more ventilated with oceanic air such as Los Angeles have slightly smaller reductions. The length of the hottest part of the day is also reduced. Advection effects on the aerosol cloud must be more carefully forecast for smaller injection regions. Verification of the impacts could be done via measurements of differences in reflected and surface downward shortwave. Such regional geoengineering applications with specific near-term target effects but smaller cost and side effects could potentially provide a means of testing larger scale applications. However, design considerations for regional applications, such as a preference for injection at a level of relatively low wind speed, differ from those for global applications. The size of the required injections and the necessity of injection close to the target region raise substantial concerns. The evaluation of this regional-scale application is thus consistent with global model evaluations, emphasizing that mitigation via

  7. High Harmonic Fast Wave Heating Experiments on NSTX

    International Nuclear Information System (INIS)

    A radio frequency (rf) system has been installed on the National Spherical Torus Experiment (NSTX) with the aim of heating the plasma and driving plasma current. The system consists of six rf transmitters, a twelve element antenna and associated transmission line components to distribute and couple the power from the transmitters to the antenna elements in a fashion to allow control of the antenna toroidal wavenumber spectrum. To date, power levels up to 3.85 MW have been applied to the NSTX plasmas. The frequency and spectrum of the rf waves has been selected to heat electrons via Landau damping and transit time magnetic pumping. The electron temperature has been observed to increase from 400 to 900 eV with little change in plasma density resulting in a plasma stored energy of 59 kJ, a toroidal beta, βT, = 10% and a normalized beta, βn = 2.7.

  8. Impact of heat waves on mortality in Croatia

    Science.gov (United States)

    Zaninović, Ksenija; Matzarakis, Andreas

    2014-08-01

    The aim of this work was to determine the criteria for heat loads associated with an increase in mortality in different climatic regions of Croatia. The relationship between heat stress and mortality was analysed for the period 1983-2008. The input series is excess mortality defined as the deviations of mortality from expected values determined by means of a Gaussian filter of 183 days. The assessment of the thermal environment was performed by means of physiologically equivalent temperature (PET). The curve depicting the relationship between mortality and temperature has a U shape, with increased mortality in both the cold and warm parts of the scale but more pronounced in the warm part. The threshold temperature for increased mortality was determined using a scatter plot and fitting data by means of moving average of mortality; the latter is defined as the temperature at which excess mortality becomes significant. The values are higher in the continental part of Croatia than at the coast due to the refreshing influence of the sea during the day. The same analysis on a monthly basis shows that at the beginning of the warm season increased mortality occurs at a lower temperature compared with later on in the summer, and the difference is up to 15 °C between August and April. The increase in mortality is highest during the first 3-5 days and after that it decreases and falls below the expected value. Long-lasting heat waves present an increased risk, but in very long heat waves the increase in mortality is reduced due to mortality displacement.

  9. Effects of Simulated Heat Waves on Cardiovascular Functions in Senile Mice

    Directory of Open Access Journals (Sweden)

    Xiakun Zhang

    2014-08-01

    Full Text Available The mechanism of the effects of simulated heat waves on cardiovascular disease in senile mice was investigated. Heat waves were simulated in a TEM1880 meteorological environment simulation chamber, according to a heat wave that occurred in July 2001 in Nanjing, China. Eighteen senile mice were divided into control, heat wave, and heat wave BH4 groups, respectively. Mice in the heat wave and heat wave BH4 groups were exposed to simulated heat waves in the simulation chamber. The levels of ET-1, NO, HSP60, SOD, TNF, sICAM-1, and HIF-1α in each group of mice were measured after heat wave simulation. Results show that heat waves decreased SOD activity in the myocardial tissue of senile mice, increased NO, HSP60, TNF, sICAM-1, and HIF-1α levels, and slightly decreased ET-1 levels, BH4 can relieve the effects of heat waves on various biological indicators. After a comprehensive analysis of the experiments above, we draw the followings conclusions regarding the influence of heat waves on senile mice: excess HSP60 activated immune cells, and induced endothelial cells and macrophages to secrete large amounts of ICAM-1, TNF-α, and other inflammatory cytokines, it also activated the inflammation response in the body and damaged the coronary endothelial cell structure, which increased the permeability of blood vessel intima and decreased SOD activity in cardiac tissues. The oxidation of lipoproteins in the blood increased, and large amounts of cholesterol were generated. Cholesterol penetrated the intima and deposited on the blood vessel wall, forming atherosclerosis and leading to the occurrence of cardiovascular disease in senile mice. These results maybe are useful for studying the effects of heat waves on elderly humans, which we discussed in the discussion chapter.

  10. Benchmarking Fast-to-Alfven Mode Conversion in a Cold MHD Plasma

    OpenAIRE

    Cally, Paul S.; Hansen, Shelley C.

    2011-01-01

    Alfv\\'en waves may be generated via mode conversion from fast magneto-acoustic waves near their reflection level in the solar atmosphere, with implications both for coronal oscillations and for active region helio-seismology. In active regions this reflection typically occurs high enough that the Alfv\\'en speed $a$ greatly exceeds the sound speed $c$, well above the $a=c$ level where the fast and slow modes interact. In order to focus on the fundamental characteristics of fast/Alfv\\'en conver...

  11. Alfven frequency modes at the edge of TFTR plasmas

    International Nuclear Information System (INIS)

    An Alfven frequency mode (AFM) is very often seen in TFTR neutral beam heated plasmas as well as ohmic plasmas. This quasi-coherent mode is so far only seen on the magnetic fluctuation diagnostics (Mirnov coils). A close correlation between the plasma edge density and the mode activity (frequency and amplitude) has been observed, which indicates that the AFM is an edge localized mode with r/a > 0.85. No direct impact of this mode on the plasma global performance or fast ion loss (e.g., the α-particles in DT experiments) has been observed. This mode is apparently not the conventional TAE (toroidicity-induced Alfven eigenmodes). The present TAE theory cannot explain the observation. Other possible explanations are discussed

  12. The development of a heat wave vulnerability index for London, United Kingdom.

    OpenAIRE

    Wolf, T; McGregor, G. R.

    2013-01-01

    The health impacts of heat waves are an emerging environmental health concern. This is especially so for large cities where there is a concentration of people and because of the urban heat island effect. Temperatures within cities can reach stressful levels during extreme temperature events. To better manage heat related health risks, information is required on the intra-urban variability of vulnerability to heat wave events. Accordingly a heat vulnerability index (HVI) is developed and prese...

  13. The Magnetic Coupling of Chromospheres and Winds From Late Type Evolved Stars: Role of MHD Waves

    Science.gov (United States)

    Airapetian, Vladimir; Leake, James; Carpenter, Kenneth

    2015-08-01

    Stellar chromospheres and winds represent universal attributes of stars on the cool portion of H-R diagram. In this paper we derive observational constrains for the chromospheric heating and wind acceleration from cool evolved stars and examine the role of Alfven waves as a viable source of energy dissipation and momentum deposition. We use a 1.5D magnetohydrodynamic code with a generalized Ohm's law to study propagation of Alfven waves generated along a diverging magnetic field in a stellar photosphere at a single frequency. We demonstrate that due to inclusion of the effects of ion-neutral collisions in magnetized weakly ionized chromospheric plasma on resistivity and the appropriate grid resolution, the numerical resistivity becomes 1-2 orders of magnitude smaller than the physical resistivity. The motions introduced by non-linear transverse Alfven waves can explain non-thermally broadened and non-Gaussian profiles of optically thin UV lines forming in the stellar chromosphere of α Tau and other late-type giant and supergiant stars. The calculated heating rates in the stellar chromosphere model due to resistive (Joule) dissipation of electric currents on Pedersen resistivity are consistent with observational constraints on the net radiative losses in UV lines and the continuum from α Tau. At the top of the chromosphere, Alfven waves experience significant reflection, producing downward propagating transverse waves that interact with upward propagating waves and produce velocity shear in the chromosphere. Our simulations also suggest that momentum deposition by non-linear Alfven waves becomes significant in the outer chromosphere within 1 stellar radius from the photosphere that initiates a slow and massive winds from red giants and supergiants.

  14. Stochastic ion heating by a lower hybrid wave. II

    Energy Technology Data Exchange (ETDEWEB)

    Karney, C.F.F.

    1979-04-01

    The motion of an ion in a coherent lower hybrid wave (characterized by vertical bar/sub parallel/vertical bar much less than vertical bar kappa/sub perpendicular to/vertical bar and ..omega.. much greater than ..cap omega../sub i/) in a tokamak plasma is studied. For ions satisfying ..nu../sub perpendicular to/ > ..omega../kappa/sub perpendicular to/, the Lorentz force law for the ions is reduced to a set of difference equations which give the Larmor radius and phase of an ion on one cyclotron orbit in terms of these quantities a cyclotron period earlier. From these difference equations an earlier result (Phys. Fluids 21, 1584(1978)) that above a certain wave amplitude the ion motion is stochastic, is readily obtained. The stochasticity threshold is given a simple physical interpretation. In addition, the difference equations are used to derive a diffusion equation governing the heating of the ions above the stochasticity threshold. By including the effects of collisions, the heating rate for the bulk ions is obtained.

  15. Stochastic ion heating by a lower hybrid wave. II

    International Nuclear Information System (INIS)

    The motion of an ion in a coherent lower hybrid wave (characterized by vertical bar/sub parallel/vertical bar much less than vertical bar kappa/sub perpendicular to/vertical bar and ω much greater than Ω/sub i/) in a tokamak plasma is studied. For ions satisfying ν/sub perpendicular to/ > ω/kappa/sub perpendicular to/, the Lorentz force law for the ions is reduced to a set of difference equations which give the Larmor radius and phase of an ion on one cyclotron orbit in terms of these quantities a cyclotron period earlier. From these difference equations an earlier result [Phys. Fluids 21, 1584(1978)] that above a certain wave amplitude the ion motion is stochastic, is readily obtained. The stochasticity threshold is given a simple physical interpretation. In addition, the difference equations are used to derive a diffusion equation governing the heating of the ions above the stochasticity threshold. By including the effects of collisions, the heating rate for the bulk ions is obtained

  16. Nonlinearly Driven Second Harmonics of Alfven Cascades

    International Nuclear Information System (INIS)

    In recent experiments on Alcator C-Mod, measurements of density fluctuations with Phase Contrast Imaging through the plasma core show a second harmonic of the basic Alfven Cascade (AC) signal. The present work describes the perturbation at the second harmonic as a nonlinear sideband produced by the Alfven Cascade eigenmode via quadratic terms in the MHD equations. (author)

  17. Computer simulations for direct conversion of the HF electromagnetic wave into the upper hybrid wave in ionospheric heating experiments

    OpenAIRE

    Ueda, H. O.; Omura, Y.; Matsumoto, H

    1998-01-01

    Excitation of upper hybrid waves associated with the ionospheric heating experiments is assumed to be essential in explaining some of the features of stimulated electromagnetic emissions (SEE). A direct conversion process is proposed as an excitation mechanism of the upper hybrid waves where the energy of an obliquely propagating electromagnetic pump wave is converted into the electrostatic upper hybrid waves due to small-scale density irregularities. We performed electromagnetic particle-in-...

  18. Alfven Wave Propagation in Young Stellar Systems

    Science.gov (United States)

    Humienny, Ray; Fatuzzo, Marco

    Young stellar systems have disks that are threaded by magnetic field lines with an hourglass geometry. These fields funnel ionizing cosmic rays (CRs) into the system. However, the effect is offset by magnetic mirroring. An previous analysis considered how the presence of magnetic turbulence moving outward from the disk would effect the propagation of cosmic-rays, and in turn, change the cosmic-ray ionization fraction occurring within the disk. This work indicated that turbulence reduces the overall flux of cosmic-rays at the disk, which has important consequences for both chemical processes and planet formation that occur within these environments. However, the analysis assumed ideal MHD condition in which the gas is perfectly coupled to the magnetic field. We explore here the validity of this assumption by solving the full equations governing the motion of both ions and neutral within the system.

  19. Generation of Alfven Waves by Magnetic Reconnection

    OpenAIRE

    Kigure, Hiromitsu; Takahashi, Kunio; Shibata, Kazunari; Yokoyama, Takaaki; Nozawa, Satoshi

    2010-01-01

    In this paper, results of 2.5-dimensional magnetohydrodynamical simulations are reported for the magnetic reconnection of non-perfectly antiparallel magnetic fields. The magnetic field has a component perpendicular to the computational plane, that is, guide field. The angle theta between magnetic field lines in two half regions is a key parameter in our simulations whereas the initial distribution of the plasma is assumed to be simple; density and pressure are uniform except for the current s...

  20. Toward a Quantitative Estimate of Future Heat Wave Mortality under Global Climate Change

    OpenAIRE

    Peng, Roger D.; Tebaldi, Claudia; McDaniel, Larry; Bobb, Jennifer; Dominici, Francesca; Bell, Michelle D.

    2010-01-01

    Background: Climate change is anticipated to affect human health by changing the distribution of known risk factors. Heat waves have had debilitating effects on human mortality, and global climate models predict an increase in the frequency and severity of heat waves. The extent to which climate change will harm human health through changes in the distribution of heat waves and the sources of uncertainty in estimating these effects have not been studied extensively. Objectives: We estimated t...

  1. Thermal bioclimate in Strasbourg - the 2003 heat wave

    Science.gov (United States)

    Matzarakis, Andreas; de Rocco, Manuela; Najjar, Georges

    2009-10-01

    This case study highlights the implications of the 2003 heat wave for the city of Strasbourg, France. The urban centers of France and other European countries were particularly affected by the heat wave. In some urban areas, the mortality rate was 60% above the expected value (Institute de Veille Sanitaire, 2003). The 2003 heat wave demonstrated once again that populations in urban centers are much more affected by extreme meteorological events than people living in rural areas. The aim of this analysis is to explore differences in thermal comfort conditions of (a) the city center of Strasbourg, and (b) its hinterland. The differences in thermal conditions existing between rural and urban areas are quantified by using a bio-climatological index termed physiologically equivalent temperature (PET). This index is based on the human energy balance and builds a relevant index for the quantification of the thermal environment of humans. We calculate the PET for the years 2003 and 2004 to highlight the temporal changes in the severity of climate extremes. The spatial scope of this study is improved compared to previous works in the field through the inclusion of PET calculations for five different sites on a central place in Strasbourg (Place Kléber). The calculations are characterized by different sky view factors and are compared to the reference site, which is located in a rural area. In the rural hinterland (Entzheim), the analysis of PET indicates a strong cold thermal stress during the winter months but no significant stress in summer. In 2003, summer temperatures were sensed as warmer compared to other years, but did not reach the extreme temperatures that may cause severe heat stress. For both the rural and the urban study sites PET was higher in the summer of 2003 than in 2004, which reflects the inferior thermal conditions in the urban area during the heat wave in 2003. For the entire study period, urban and rural day-time PET reached similar maximal values

  2. The impact of heat, cold, and heat waves on hospital admissions in eight cities in Korea

    Science.gov (United States)

    Son, Ji-Young; Bell, Michelle L.; Lee, Jong-Tae

    2014-01-01

    Although the impact of temperature on mortality is well documented, relatively fewer studies have evaluated the associations of temperature with morbidity outcomes such as hospital admissions, and most studies were conducted in North America or Europe. We evaluated weather and hospital admissions including specific causes (allergic disease, asthma, selected respiratory disease, and cardiovascular disease) in eight major cities in Korea from 2003 to 2008. We also explored potential effect modification by individual characteristics such as sex and age. We used hierarchical modeling to first estimate city-specific associations between heat, cold, or heat waves and hospitalizations, and then estimated overall effects. Stratified analyses were performed by cause of hospitalization, sex, and age (0-14, 15-64, 65-74, and ≥75 years). Cardiovascular hospitalizations were significantly associated with high temperature, whereas hospitalizations for allergic disease, asthma, and selected respiratory disease were significantly associated with low temperature. The overall heat effect for cardiovascular hospitalization was a 4.5 % (95 % confidence interval 0.7, 8.5 %) increase in risk comparing hospitalizations at 25 to 15 °C. For cold effect, the overall increase in risk of hospitalizations comparing 2 with 15 °C was 50.5 (13.7, 99.2 %), 43.6 (8.9, 89.5 %), and 53.6 % (9.8, 114.9 %) for allergic disease, asthma, and selected respiratory disease, respectively. We did not find statistically significant effects of heat waves compared with nonheat wave days. Our results suggest susceptible populations such as women and younger persons. Our findings provide suggestive evidence that both high and low ambient temperatures are associated with the risk of hospital admissions, particularly in women or younger person, in Korea.

  3. The impact of heat waves on mortality in 9 European cities: results from the EuroHEAT project

    Directory of Open Access Journals (Sweden)

    Bisanti Luigi

    2010-07-01

    Full Text Available Abstract Background The present study aimed at developing a standardized heat wave definition to estimate and compare the impact on mortality by gender, age and death causes in Europe during summers 1990-2004 and 2003, separately, accounting for heat wave duration and intensity. Methods Heat waves were defined considering both maximum apparent temperature and minimum temperature and classified by intensity, duration and timing during summer. The effect was estimated as percent increase in daily mortality during heat wave days compared to non heat wave days in people over 65 years. City specific and pooled estimates by gender, age and cause of death were calculated. Results The effect of heat waves showed great geographical heterogeneity among cities. Considering all years, except 2003, the increase in mortality during heat wave days ranged from + 7.6% in Munich to + 33.6% in Milan. The increase was up to 3-times greater during episodes of long duration and high intensity. Pooled results showed a greater impact in Mediterranean (+ 21.8% for total mortality than in North Continental (+ 12.4% cities. The highest effect was observed for respiratory diseases and among women aged 75-84 years. In 2003 the highest impact was observed in cities where heat wave episode was characterized by unusual meteorological conditions. Conclusions Climate change scenarios indicate that extreme events are expected to increase in the future even in regions where heat waves are not frequent. Considering our results prevention programs should specifically target the elderly, women and those suffering from chronic respiratory disorders, thus reducing the impact on mortality.

  4. Electron heating by mode-converted ion-Bernstein waves in ICRF heating of tokamak plasmas

    International Nuclear Information System (INIS)

    In a tokamak plasma, ion-Bernstein waves (IBW) can be excited by mode-conversion of the externally launched fast wave for ICRF heating. This conversion process is known to be efficient for low k/sub parallel/'s which carry substantial power from a single loop antenna. A detailed numerical analysis of the propagation of the IBW shows that the initial small k/sub parallel/ are significantly enhanced along the rays due to toroidal effects. The upshift can occur for short radial distances of propagation and is large enough so that the IBW can Landau damp onto the electrons. This could help explain the observed strong electron heating by ICRF waves in tokamak plasmas. The numerical ray trajectory analysis is done in toroidal geometry for a hot Maxwellian plasma with gradients in temperature, density, toroidal and poloidal magnetic fields included in a WKB sense. A simple analytical model is derived which explains the upshift in k/sub parallel/ and gives results very close to the numerically obtained values. Approximate analytical conditions for appreciable electron Landau damping of the IBW are also given

  5. Three-dimensional computation of drift Alfven turbulence

    International Nuclear Information System (INIS)

    A transcollisional, electromagnetic fluid model, incorporating the parallel heat flux as a dependent variable, is constructed to treat electron drift turbulence in the regime of tokamak edge plasma at the L-H transition. The resulting turbulence is very sensitive to the plasma beta throughout this regime, with the scaling with rising beta produced by the effect of magnetic induction to slow the Alfvenic parallel electron dynamics and thereby leave the turbulence in a more robust, non-adiabatic state. Magnetic flutter and curvature have a minor quantitative effect is strong. Transport by magnetic flutter is small compared to that by the E x B flow eddies. Fluctuation statistics show that while the turbulence shows no coherent structure, it is coupled strongly enough so that neither density nor temperature fluctuations behave as passive scalars. Both profile gradients drive the turbulence, with the total thermal energy transport varying only weakly with the gradient ratio, d log T/d log n. Scaling with magnetic shear is pronounced, with stronger shear leading to lower drive levels. Scaling with either collision frequency or magnetic curvature is weak, consistent with their weak qualitative effect. The result is that electron drift turbulence at L-H transition edge parameters is drift Alfven turbulence, with both ballooning and resistivity in a clear secondary role. The contents of the drift Alfven model will form a significant part of any useful first-principles computation of tokamak edge turbulence. (Author)

  6. Bleaching absorption fronts and beam propagation in laser-heated solenoids

    International Nuclear Information System (INIS)

    It is shown that the propagation velocity of bleaching laser-driven heating waves in the supersonic mode is governed by the requirement that the bleached plasma maintains an optical thickness of unity. It is proposed that in the case where the bleached plasma is confined by very large magnetic fields, the diameter of the plasma column may self-regulate so that the bleaching wave propagates at the Alfven velocity

  7. Heat Wave-Associated Vibriosis, Sweden and Finland, 2014.

    Science.gov (United States)

    Baker-Austin, Craig; Trinanes, Joaquin A; Salmenlinna, Saara; Löfdahl, Margareta; Siitonen, Anja; Taylor, Nick G H; Martinez-Urtaza, Jaime

    2016-07-01

    During summer 2014, a total of 89 Vibrio infections were reported in Sweden and Finland, substantially more yearly infections than previously have been reported in northern Europe. Infections were spread across most coastal counties of Sweden and Finland, but unusually, numerous infections were reported in subarctic regions; cases were reported as far north as 65°N, ≈100 miles (160 km) from the Arctic Circle. Most infections were caused by non-O1/O139 V. cholerae (70 cases, corresponding to 77% of the total, all strains were negative for the cholera toxin gene). An extreme heat wave in northern Scandinavia during summer 2014 led to unprecedented high sea surface temperatures, which appear to have been responsible for the emergence of Vibrio bacteria at these latitudes. The emergence of vibriosis in high-latitude regions requires improved diagnostic detection and clinical awareness of these emerging pathogens. PMID:27314874

  8. Stochastic ion heating by a lower hybrid wave

    Energy Technology Data Exchange (ETDEWEB)

    Karney, C.F.F.

    1978-04-01

    The motion of an ion in a lower hybrid wave in a tokamak type plasma is studied. For ions with ..nu../sub perpendicular to/ approximately greater than ..omega../k/sub perpendicular to/ the motion is stochastic for fields satisfying E/B/sub 0/ greater than /sup 1///sub 4/ (..cap omega../sub i//..omega..)/sup /sup 1///sub 3//(..omega../k/sub perpendicular to/). Provided the perpendicular phase velocity, ..omega../k/sub perpendicular to/, can be slowed down to a few times the ion thermal speed, this stochastic ion motion may be an important mechanism by which injected rf power near the lower hybrid frequency can directly heat the ions.

  9. Electron transport in Tore Supra with fast wave electron heating

    International Nuclear Information System (INIS)

    The hot electron plasmas (Te > 2Ti) in Tore Supra driven by Fast Wave Electron Heating (FWEH) are analyzed for thermal transport. Both neoclassical and anomalous transport processes are taken into account. The dominant power flow is through the electron channel of anomalous thermal diffusivity. The electron and ion temperature gradient driven instabilities are analyzed for a well documented discharge and shown to explain the diffusivities inferred from the steady power balance analysis. The discharges are maintained in a quasi-steady state for periods up to one hundred global energy replacement times. A large Tore Supra database is tested against two models for the turbulent electron thermal conductivity Good correlation is obtained with an updated version of the collisionless skin depth formula. The electrostatic turbulence-based formula performs poorly in the core but well in the outer plasma. The electromagnetic turbulence theory based formula is benchmarked with the empirical Taroni-Bohm formula derived from JET data. (author)

  10. Symplectic Reconstruction of Data for Heat and Wave Equations

    CERN Document Server

    Carlsson, Jesper

    2008-01-01

    This report concerns the inverse problem of estimating a spacially dependent coefficient of a partial differential equation from observations of the solution at the boundary. Such a problem can be formulated as an optimal control problem with the coefficient as the control variable and the solution as state variable. The heat or the wave equation is here considered as state equation. It is well known that such inverse problems are ill-posed and need to be regularized. The powerful Hamilton-Jacobi theory is used to construct a simple and general method where the first step is to analytically regularize the Hamiltonian; next its Hamiltonian system, a system of nonlinear partial differential equations, is solved with the Newton method and a sparse Jacobian.

  11. Localized electron heating experiments by ion Bernstein wave in the TNT-A tokamak

    International Nuclear Information System (INIS)

    Plasma heating by ion Bernstein wave in the range of 2 ωD D is investigated in deuterium dominant plasma of the TNT-A tokamak. The localized electron heating is observed at the harmonic (3 ωD) and subharmonic (2.5 ωD) resonance layers, while the electron heating on the whole plasma region is observed at ω = 2 ωD. It is also shown that the heating is efficient and heating layer is localized by ion Bernstein wave in comparison with fast magnetosonic wave. (author)

  12. Chromospheric heating by acoustic waves compared to radiative cooling

    CERN Document Server

    Sobotka, M; Švanda, M; Jurčák, J; del Moro, D; Berrilli, F

    2016-01-01

    Acoustic and magnetoacoustic waves are among the possible candidate mechanisms that heat the upper layers of solar atmosphere. A weak chromospheric plage near a large solar pore NOAA 11005 was observed on October 15, 2008 in the lines Fe I 617.3 nm and Ca II 853.2 nm with the Interferometric Bidimemsional Spectrometer (IBIS) attached to the Dunn Solar Telescope. Analyzing the Ca II observations with spatial and temporal resolutions of 0.4" and 52 s, the energy deposited by acoustic waves is compared with that released by radiative losses. The deposited acoustic flux is estimated from power spectra of Doppler oscillations measured in the Ca II line core. The radiative losses are calculated using a grid of seven 1D hydrostatic semi-empirical model atmospheres. The comparison shows that the spatial correlation of maps of radiative losses and acoustic flux is 72 %. In quiet chromosphere, the contribution of acoustic energy flux to radiative losses is small, only of about 15 %. In active areas with photospheric ma...

  13. Study of the Hamiltonian of the response of a tokamak plasma to the ion cyclotron heating wave: minor heating and generation of current by a fast wave

    International Nuclear Information System (INIS)

    The role of additional heatings, such as the ion Cyclotron heating, is to raise magnetic fusion plasmas to higher temperatures, to satisfy the ignition condition. The understanding of the wave absorption mechanisms by the plasma requires a precise description of the particle individual trajectories. The Hamiltonian mechanics, through action-angle variables, allows this description, and makes the computation of the wave-particle interaction easier. A quantitative evaluation of the intrinsic stochasticity is derived for ionic trajectories perturbated by the fast wave. The results show the importance of the Hamiltonian chaos in the formation of the deeply anisotropic distribution tails, encountered in minor heating scenarios. Direct interaction of the electrons and the fast wave is analysed. The influence of the various parameters is examined in order to optimize this scenario of fast wave current drive in tokamaks

  14. Shock Waves and Turbulent Heating in Low-Density Plasmas

    International Nuclear Information System (INIS)

    Shock heating and shock structures are studied in theta-pinch-like devices in a wide range of plasma parameters ne, B1, mi, and of wave speeds u1 (3 x 106 cms-1 ≤ u1 ≤ 108 cm-1). Densities and temperatures were determined locally by interferometry and by Thomson scattering. Magnetic and electric fields were measured with small high-frequency probes. Previous investigations of perpendicular, hydromagnetic shocks at β1 A A, critical at densities above 1014 cm-3 are extended to densities close to 1013 cm-3 and to other mass ratios me/mi. Shocks are nearly collision-free even with respect to the initial state. A scaling law is obtained for the effective collision frequency veff, deduced from measured turbulent-heating rates and current densities. Results show that veff ≈ 10-3 (Te/Ti) (vd/cs) ωpi. Studies are extended to small Alfvén-Mach numbers, where shock structures are still collision-dominated. Comparison with theory shows good agreement. In the same density range, shocks are generated at β1 ≈ 0.3, and with MA >> MA critical- from the observed election heating rates and the electron density jump, together with the shock relations, estimates for turbulent ion-heating rates are obtained. Investigation of the structure of collision-dominated shocks in magnetic field-free plasma shows that electron temperature and density front are well separated; the width of separation agrees with theoretical estimates. Attempts are made to heat low-density (n ≤ 1013 cm-3), magnetic-field-free plasma by fast magnetic compression. In deuterium, an anomalously broad current sheath is observed. Nevertheless, deuteron temperatures of ≈ 10 keV and relatively high values of the local β (β ≈ 10) are achieved in a low-energy theta-pinch (≈ 10 kj) . Electric and magnetic field fluctuations of large amplitude occur. In argon, at large radii, a stationary electromagnetic sheath is found with a width of a few c/ωpe and an electric potential jump as required by theory. Ion

  15. Contrasting responses of urban and rural surface energy budgets to heat waves explain synergies between urban heat islands and heat waves

    International Nuclear Information System (INIS)

    Heat waves (HWs) are projected to become more frequent and last longer over most land areas in the late 21st century, which raises serious public health concerns. Urban residents face higher health risks due to synergies between HWs and urban heat islands (UHIs) (i.e., UHIs are higher under HW conditions). However, the responses of urban and rural surface energy budgets to HWs are still largely unknown. This study analyzes observations from two flux towers in Beijing, China and reveals significant differences between the responses of urban and rural (cropland) ecosystems to HWs. It is found that UHIs increase significantly during HWs, especially during the nighttime, implying synergies between HWs and UHIs. Results indicate that the urban site receives more incoming shortwave radiation and longwave radiation due to HWs as compared to the rural site, resulting in a larger radiative energy input into the urban surface energy budget. Changes in turbulent heat fluxes also diverge strongly for the urban site and the rural site: latent heat fluxes increase more significantly at the rural site due to abundant available water, while sensible heat fluxes and possibly heat storage increase more at the urban site. These comparisons suggest that the contrasting responses of urban and rural surface energy budgets to HWs are responsible for the synergies between HWs and UHIs. As a result, urban mitigation and adaption strategies such as the use of green roofs and white roofs are needed in order to mitigate the impact of these synergies. (letter)

  16. Urban warming in the 2013 summer heat wave in eastern China

    Science.gov (United States)

    Wang, Jun; Yan, Zhongwei; Quan, Xiao-Wei; Feng, Jinming

    2016-06-01

    The impact of urban warming during the 2013 July-August extreme heat wave event across the Yangtze River Delta (YRD) in China was assessed. Using a newly developed high-resolution, land-use dataset, urban stations were identified from a total of 101 stations in the YRD. The difference between urban and non-urban/rural stations indicates that urban warming reached 1.22 °C in the 2013 summer heat wave. The new land-use dataset was then input to the Weather Research and Forecasting model to further understand the dynamical/physical processes of the urban warming during the heat wave. The model-simulated urban warming is ~1.5 °C. Impacts of urbanization on near-surface temperature had strong diurnal variation, reaching a peak at 19:00 LST, around sunset. In the daytime, urban warming was mainly caused by enhanced sensible heat fluxes and longwave radiation from the surface. Because of reduced latent heat flux and increased heat capacity, urban ground stored much more heat than rural ground during the daytime, which is later released as sensible heat flux from the surface at night, leading to the nocturnal urban warming. The simulation results also suggest a positive feedback between urban warming and heat wave intensity, which makes the heat wave more intense in urban than rural areas and the urban warming during the extreme heat wave stronger than its climatological mean.

  17. Stochastic acceleration of ions driven by Pc1 wave packets

    International Nuclear Information System (INIS)

    The stochastic motion of protons and He+ ions driven by Pc1 wave packets is studied in the context of resonant particle heating. Resonant ion cyclotron heating typically occurs when wave powers exceed 10−4 nT2/Hz. Gyroresonance breaks the first adiabatic invariant and energizes keV ions. Cherenkov resonances with the electrostatic component of wave packets can also accelerate ions. The main effect of this interaction is to accelerate thermal protons to the local Alfven speed. The dependencies of observable quantities on the wave power and plasma parameters are determined, and estimates for the heating extent and rate of particle heating in these wave-particle interactions are shown to be in reasonable agreement with known empirical data

  18. Enzyme Activity Dynamics in Response to Climate Change: 2011 Drought-Heat Wave

    Science.gov (United States)

    Extreme weather events such as severe droughts and heat waves may have permanent consequences on soil quality and functioning in agroecosystems. The Southern High Plains (SHP) region of Texas, U.S., a large cotton producing area, experienced a historically extreme drought and heat wave during 2011,...

  19. The role of Alfvén wave heating in solar prominences

    Science.gov (United States)

    Soler, Roberto; Terradas, Jaume; Oliver, Ramon; Ballester, Jose Luis

    2016-07-01

    Observations have shown that magnetohydrodynamic waves over a large frequency range are ubiquitous in solar prominences. The waves are probably driven by photospheric motions and may transport energy up to prominences suspended in the corona. Dissipation of wave energy can lead to heating of the cool prominence plasma, thereby contributing to the local energy balance within the prominence. Here we discuss the role of Alfvén wave dissipation as a heating mechanism for the prominence plasma. We consider a slab-like quiescent prominence model with a transverse magnetic field embedded in the solar corona. The prominence medium is modeled as a partially ionized plasma composed of a charged ion-electron single fluid and two separate neutral fluids corresponding to neutral hydrogen and neutral helium. Friction between the three fluids acts as a dissipative mechanism for the waves. The heating caused by Alfvén waves incident on the prominence slab is analytically explored. We find that the dense prominence slab acts as a resonant cavity for the waves. The fraction of incident wave energy that is channeled into the slab strongly depends upon the wave period, P. Using typical prominence conditions, we obtain that wave energy trapping and associated heating are negligible when P ≳ 100 s, so that it is unlikely that those waves have a relevant influence on prominence energetics. When 1 s ≲ P ≲ 100 s the energy absorption into the slab shows several sharp and narrow peaks that can reach up to ~100% when the incident wave frequency matches a cavity resonance of the slab. Wave heating is enhanced at those resonant frequencies. Conversely, when P ≲ 1 s cavity resonances are absent, but the waves are heavily damped by the strong dissipation. We estimate that wave heating may compensate for about 10% of radiative losses of the prominence plasma.

  20. Characterization of Heat-Wave Propagation through Laser-Driven Ti-Doped Underdense Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Tanabe, M; Nishimura, H; Ohnishi, N; Fournier, K B; Fujioka, S; Iwamae, A; Hansen, S B; Nagai, K; Girard, F; Primout, M; Villette, B; Brebion, D; Mima, K

    2009-02-23

    The propagation of a laser-driven heat-wave into a Ti-doped aerogel target was investigated. The temporal evolution of the electron temperature was derived by means of Ti K-shell x-ray spectroscopy, and compared with two-dimensional radiation hydrodynamic simulations. Reasonable agreement was obtained in the early stage of the heat-wave propagation. In the later phase, laser absorption, the propagation of the heat wave, and hydrodynamic motion interact in a complex manner, and the plasma is mostly re-heated by collision and stagnation at the target central axis.

  1. The Difficulty of the Heating of Cluster Cooling Flows by Sound Waves and Weak Shocks

    OpenAIRE

    Fujita, Yutaka; Suzuki, Takeru Ken

    2006-01-01

    We investigate heating of the cool core of a galaxy cluster through the dissipation of sound waves and weak shocks excited by the activities of the central active galactic nucleus (AGN). Using a weak shock theory, we show that this heating mechanism alone cannot reproduce observed temperature and density profiles of a cluster, because the dissipation length of the waves is much smaller than the size of the core and thus the wave energy is not distributed to the whole core.

  2. Characterization of Heat Waves in the Sahel and associated mechanisms

    Science.gov (United States)

    Oueslati, Boutheina; Pohl, Benjamin; Moron, Vincent; Rome, Sandra

    2016-04-01

    Large efforts are made to investigate the heat waves (HW) in developed countries because of their devastating impacts on society, economy and environment. This interest increased after the intense event over Europe during summer 2003. However, HWs are still understudied over developing countries. This is particularly true in West Africa, and especially in the Sahel, where temperatures recurrently reach critical values, such as during the 2010 HW event. Understanding the Sahelian HWs and associated health risks constitute the main objective of ACASIS, a 4-year project funded by the French Agence Nationale de la Recherche. Our work contributes to this project and aims at characterizing the Sahelian HWs and understanding the mechanisms associated with such extreme events. There is no universal definition of a HW event, since it is highly dependent on the sector (human health, agriculture, transport...) and region of interest. In our case, a HW is defined when the heat index of the day and of the night exceeds the 90th percentile for at least 3 consecutive days (Rome et al. 2016, in preparation). This index combines temperature and relative humidity in order to determine the human-perceived equivalent temperature (definition adapted from Steadman, 1979). Intrinsic properties of Sahelian HW are analyzed from the Global Summary of the Day (GSOD) synoptic observations and ERA-interim reanalyses over 1979-2014 during boreal spring seasons (April-May-June), the warmest period of the year in the Central Sahel. ERA-interim captures well the observed interannual variability and seasonal cycle at the regional scale, as well as the 1979-2014 increasing linear trend of springtime HW occurrences in the Sahel. Reanalyses, however, overestimate the duration, spatial extent of HW, and underestimate their intensity. For both GSOD and ERA-interim, we show that, over the last three decades, Sahelian HWs tend to become more frequent, last longer, cover larger areas and reach higher

  3. Changes of western European heat wave characteristics projected by the CMIP5 ensemble

    Science.gov (United States)

    Schoetter, Robert; Cattiaux, Julien; Douville, Hervé

    2015-09-01

    We investigate heat waves defined as periods of at least 3 consecutive days of extremely high daily maximum temperature affecting at least 30 % of western Europe. This definition has been chosen to select heat waves that might impact western European electricity supply. Even though not all such heat waves threaten it, the definition allows to identify a sufficient number of events, the strongest being potentially harmful. The heat waves are characterised by their duration, spatial extent, intensity and severity. The heat wave characteristics are calculated for historical and future climate based on results of climate model simulations conducted during the 5th Phase of the Coupled Model Intercomparison Project (CMIP5). The uncertainty of future anthropogenic forcing is taken into account by analysing results for the Representative Concentration Pathway scenarios RCP2.6, RCP4.5 and RCP8.5. The historical simulations are evaluated against the EOBS gridded station data. The CMIP5 ensemble median captures well the observed mean heat wave characteristics. However, no model simulates a heat wave as severe as observed during August 2003. Under future climate conditions, the heat waves become more frequent and have higher mean duration, extent and intensity. The ensemble spread is larger than the scenario uncertainty. The shift of the temperature distribution is more important for the increase of the cumulative heat wave severity than the broadening of the temperature distribution. However, the broadening leads to an amplification of the cumulative heat wave severity by a factor of 1.7 for RCP4.5 and 1.5 for RCP8.5.

  4. Linear gyrokinetic particle-in-cell simulations of Alfven instabilities in tokamaks

    CERN Document Server

    Biancalani, A; Briguglio, S; Koenies, A; Lauber, Ph; Mishchenko, A; Poli, E; Scott, B D; Zonca, F

    2015-01-01

    The linear dynamics of Alfven modes in tokamaks is investigated here by means of the global gyrokinetic particle-in-cell code NEMORB. The model equations are shown and the local shear Alfven wave dispersion relation is derived, recovering the continuous spectrum in the incompressible ideal MHD limit. A verification and benchmark analysis is performed for continuum modes in a cylinder and for toroidicity-induced Alfven Eigenmodes. Modes in a reversed-shear equilibrium are also investigated, and the dependence of the spatial structure in the poloidal plane on the equilibrium parameters is described. In particular, a phase-shift in the poloidal angle is found to be present for modes whose frequency touches the continuum, whereas a radial symmetry is found to be characteristic of modes in the continuum gap.

  5. Alpha particle destabilization of the toroidicity-induced Alfven eigenmodes

    International Nuclear Information System (INIS)

    The high frequency, low mode number toroidicity-induced Alfven eigenmodes (TAE) are shown to be driven unstable by the circulating and/or trapped α-particles through the wave-particle resonances. Satisfying the resonance condition requires that the α-particle birth speed vα ≥ vA/2|m-nq|, where vA is the Alfven speed, m is the poloidal model number, and n is the toroidal mode number. To destabilize the TAE modes, the inverse Landau damping associated with the α-particle pressure gradient free energy must overcome the velocity space Landau damping due to both the α-particles and the core electrons and ions. The growth rate was studied analytically with a perturbative formula derived from the quadratic dispersion relation, and numerically with the aid of the NOVA-K code. Stability criteria in terms of the α-particle beta βα, α-particle pressure gradient parameter (ω*/ωA) (ω* is the α-particle diamagnetic drift frequency), and (vα/vA) parameters will be presented for TFTR, CIT, and ITER tokamaks. The volume averaged α-particle beta threshold for TAE instability also depends sensitively on the core electron and ion temperature. Typically the volume averaged α-particle beta threshold is in the order of 10-4. Typical growth rates of the n=1 TAE mode can be in the order of 10-2ωA, where ωA=vA/qR. Other types of global Alfven waves are stable in D-T tokamaks due to toroidal coupling effects

  6. Nonlinear gyrokinetic equations for low-frequency electromagnetic waves in general plasma equilibria

    International Nuclear Information System (INIS)

    A nonlinear gyrokinetic formalism for low-frequency (less than the cyclotron frequency) microscopic electromagnetic perturbations in general magnetic field configurations is developed. The nonlinear equations thus derived are valid in the strong-turbulence regime and contain effects due to finite Larmor radius, plasma inhomogeneities, and magentic field geometries. The specific case of axisymmetric tokamaks is then considered, and a model nonlinear equation is derived for electrostatic drift waves. Also, applying the formalism to the shear Alfven wave heating sceme, it is found that nonlinear ion Landau damping of kinetic shear-Alfven waves is modified, both qualitatively and quantitatively, by the diamagnetic drift effects. In particular, wave energy is found to cascade in wavenumber instead of frequency

  7. The characteristic of heat wave effects on coronary heart disease mortality in Beijing, China: a time series study.

    Directory of Open Access Journals (Sweden)

    Zhaoxing Tian

    Full Text Available BACKGROUND: There is limited evidence for the impacts of heat waves on coronary heart disease (CHD mortality in Beijing, capital city of China. OBJECTIVES: We aimed to find a best heat wave definition for CHD mortality; and explore the characteristic of heat wave effects on CHD in Beijing, China. METHODS: We obtained daily data on weather and CHD mortality in Beijing for years 2000-2011. A quasi-Poisson regression model was used to assess the short-term impact of heat waves on CHD mortality in hot season (May-September, while controlling for relative humidity, day of the week, long-term trend and season. We compared 18 heat wave definitions by combining heat wave thresholds (87.5(th, 90.0(th, 92.5(th, 95(th, 97.5(th, and 99(th percentile of daily mean temperature with different duration days (≥ 2 to ≥ 4 days, using Akaike information criterion for quasi-Poisson. We examined whether heat wave effects on CHD mortality were modified by heat wave duration and timing. RESULTS: Heat wave definition using 97.5(th percentile of daily mean temperature (30.5 °C and duration ≥ 2 days produced the best model fit. Based on this heat wave definition, we found that men and elderly were sensitive to the first heat waves of the season, while women and young were sensitive to the second heat waves. In general, the longer duration of heat waves increased the risks of CHD mortality more than shorter duration for elderly. The first two days of heat waves had the highest impact on CHD mortality. Women and elderly were at higher risks than men and young when exposed to heat waves, but the effect differences were not statistically significant. CONCLUSIONS: Heat waves had significant impact on CHD mortality. This finding may have implications for policy making towards protecting human health from heat waves.

  8. Projections of heat waves with high impact on human health in Europe

    Science.gov (United States)

    Amengual, A.; Homar, V.; Romero, R.; Brooks, H. E.; Ramis, C.; Gordaliza, M.; Alonso, S.

    2014-08-01

    Climate change will result in more intense, more frequent and longer lasting heat waves. The most hazardous conditions emerge when extreme daytime temperatures combine with warm night-time temperatures, high humidities and light winds for several consecutive days. Here, we assess present and future heat wave impacts on human health in Europe. Present daily physiologically equivalent temperatures (PET) are derived from the ERA-Interim reanalysis. PET allows to specifically focus on heat-related risks on humans. Regarding projections, a suite of high-resolution regional climate models - run under SRES A1B scenario - has been used. A quantile-quantile adjustment is applied to the daily simulated PET to correct biases in individual model climatologies and a multimodel ensemble strategy is adopted to encompass model errors. Two types of heat waves differently impacting human health - strong and extreme stress - are defined according to specified thresholds of thermal stress and duration. Heat wave number, frequency, duration and amplitude are derived for each type. Results reveal relatively strong correlations between the spatial distribution of strong and extreme heat wave amplitudes and mortality excess for the 2003 European summer. Projections suggest a steady increase and a northward extent of heat wave attributes in Europe. Strong stress heat wave frequencies could increase more than 40 days, lasting over 20 days more by 2075-2094. Amplitudes might augment up to 7 °C per heat wave day. Important increases in extreme stress heat wave attributes are also expected: up to 40 days in frequency, 30 days in duration and 4 °C in amplitude. We believe that with this information at hand policy makers and stakeholders on vulnerable populations to heat stress can respond more effectively to the future challenges imposed by climate warming.

  9. Magnitude and frequency of heat and cold waves in recent decades: the case of South America

    Science.gov (United States)

    Ceccherini, Guido; Russo, Simone; Ameztoy, Iban; Romero, Claudia Patricia; Carmona-Moreno, Cesar

    2016-03-01

    In recent decades there has been an increase in magnitude and occurrence of heat waves and a decrease of cold waves, both of which may be related to the anthropogenic influence. This study describes the extreme temperature regime of heat waves and cold waves across South America over recent years (1980-2014). Temperature records come from the Global Surface Summary of the Day (GSOD), a climatological data set produced by the National Climatic Data Center that provides records of daily maximum and minimum temperatures acquired worldwide. The magnitude of heat waves and cold waves for each GSOD station are quantified on an annual basis by means of the Heat Wave Magnitude Index and the Cold Wave Magnitude Index. Results indicate an increase in intensity and in frequency of heat waves, especially in the last 10 years. Conversely, no significant changes are detected for cold waves. In addition, the trend of the annual temperature range (i.e. yearly mean of Tmax - yearly mean of Tmin) is positive - up to 1 °C per decade - over the extratropics and negative - up to 0.5 °C per decade - over the tropics.

  10. The Effect of Heat Waves on Mental Health in a Temperate Australian City

    OpenAIRE

    Hansen, Alana; Bi, Peng; Nitschke, Monika; Ryan, Philip; Pisaniello, Dino; Tucker, Graeme

    2008-01-01

    Objective The goal of this study was to identify mental, behavioral, and cognitive disorders that may be triggered or exacerbated during heat waves, predisposing individuals to heat-related morbidity and mortality. Design Using health outcome data from Adelaide, South Australia, for 1993–2006, we estimated the effect of heat waves on hospital admissions and mortalities attributed to mental, behavioral, and cognitive disorders. We analyzed data using Poisson regression accounting for overdispe...

  11. Synoptic-scale characteristics and atmospheric controls of summer heat waves in China

    Science.gov (United States)

    Wang, Weiwen; Zhou, Wen; Li, Xiuzhen; Wang, Xin; Wang, Dongxiao

    2016-05-01

    Summer heat waves with persistent extreme high temperatures have been occurring with increasing frequency in recent decades. These extreme events have disastrous consequences for human health, economies, and ecosystems. In this study, we examine three summers with intense and protracted heat waves: the summers of 2003, 2006, and 2013, with high temperatures located mainly in southeastern, southwestern, and eastern China, respectively. The synoptic-scale characteristics of these heat waves and associated atmospheric circulation anomalies are investigated. In the early heat wave episode of 2003, a heat center was located in the southeast coastal provinces during the first 20 days of July. The maximum southward displacement of the East Asian jet stream (EAJS) induced anticyclonic anomalies to the south, associated with southwestward intensification of the western North Pacific subtropical high (WNPSH), and extreme high temperatures were found only to the south of the Yangtze River. In the later episode, a poleward displacement of the EAJS and an enhanced WNPSH over the midlatitudes of eastern China resulted in a "heat dome" over the region, and the heat wave extended northward to cover a larger area of eastern China. The coupling between the westward-enhanced WNPSH and poleward-displaced EAJS was found in the East China heat wave of 2013 as well. But the area of high temperatures reached far to the north in August 2013, with below-normal temperatures located in a small region of South China. In the 2006 southwestern drought and heat wave, extreme poleward displacement of the EAJS, associated with extraordinary westward extension of the WNSPH, resulted in further blocking of the moisture supply from the southwest monsoon. Large-scale moisture deficiencies, dry conditions, and downslope winds were common features of all investigated heat wave episodes. But in 2006, low-level heat lows associated with a well-mixed layer due to intensive daytime heating and atmospheric

  12. Health impacts of the July 2010 heat wave in Québec, Canada

    Directory of Open Access Journals (Sweden)

    Bustinza Ray

    2013-01-01

    Full Text Available Abstract Background One of the consequences of climate change is the increased frequency and intensity of heat waves which can cause serious health impacts. In Québec, July 2010 was marked by an unprecedented heat wave in recent history. The purpose of this study is to estimate certain health impacts of this heat wave. Methods The crude daily death and emergency department admission rates during the heat wave were analyzed in relation to comparison periods using 95% confidence intervals. Results During the heat wave, the crude daily rates showed a significant increase of 33% for deaths and 4% for emergency department admissions in relation to comparison periods. No displacement of mortality was observed over a 60-day horizon. Conclusions The all-cause death indicator seems to be sufficiently sensitive and specific for surveillance of exceedences of critical temperature thresholds, which makes it useful for a heat health-watch system. Many public health actions combined with the increased use of air conditioning in recent decades have contributed to a marked reduction in mortality during heat waves. However, an important residual risk remains, which needs to be more vigorously addressed by public health authorities in light of the expected increase in the frequency and severity of heat waves and the aging of the population.

  13. Impact of heat waves on nonaccidental deaths in Jinan, China, and associated risk factors

    Science.gov (United States)

    Zhang, Jun; Liu, Shouqin; Han, Jing; Zhou, Lin; Liu, Yueling; Yang, Liu; Zhang, Ji; Zhang, Ying

    2016-01-01

    An ecological study and a case-crossover analysis were conducted to evaluate the impact of heat waves on nonaccidental deaths, and to identify contributing factors of population vulnerability to heat-related deaths in Jinan, China. Daily death data and meteorological data were collected for summer months (June to August) of 2012-2013. Excess mortality was calculated and multivariate linear regression models were used to assess the increased risk of heat waves on deaths. Univariate and multivariate logistic regression models were performed to estimate the odd ratios (ORs) of risk factors and their 95 % confidence intervals (CIs). Overall, heat waves were related to 24.88 % excess deaths of total nonaccidental deaths and 31.33 % excess deaths of circulatory diseases, with an OR of 16.07 (95 % CI 8.80-23.33) for total nonaccidental deaths and 12.46 (95 % CI 7.39-17.53) for deaths of circulatory diseases. The case-crossover analysis indicated that older people were more likely to die during heat waves (OR = 1.233, 95 % CI 1.076-1.413) and more deaths occurred outside a hospital during heat waves (OR = 1.142, 95 % CI 1.006-1.296). In conclusion, heat waves have caused excess deaths and significantly increased the risk of circulatory deaths. The risk factors identified in our study have implications for public health interventions to reduce heat-related mortality during extreme heat events.

  14. Observation of modes at frequencies near the second Alfven gap in TFTR

    International Nuclear Information System (INIS)

    Modes have been observed near the frequency of the second Alfven gap during off-axis H-minority heating experiments in the circular cross-section Tokamak Fusion Test Reactor. The observation of these modes is surprising in that the second gap, which is generally opened with ellipticity, is expected to be small, of order (r/R)2. A model is proposed in which the second gap is opened by the fast ion beta, which is shown to be able to introduce mode coupling, much as toroidal effects introduce mode coupling for Toroidal Alfven Eigenmodes (TAE). The modes are seen with and without accompanying TAE mode activity

  15. Modifying Effect of Heat Waves on the Relationship between Temperature and Mortality.

    Science.gov (United States)

    Lee, Won Kyung; Lee, Hye Ah; Park, Hyesook

    2016-05-01

    Studies conducted to evaluate temporal trends of heat-related mortality have not considered the effects of heat waves; although it is known they can affect mortality and act as a modifying factor. After adjusting for long-term trends and seasonality, the effects of temperature on non-accidental deaths in Seoul and Busan (inland and coastal cities, respectively) were analyzed using a generalized additive model of Poisson distribution. We evaluated temporal trends of heat-related mortalities in four periods (1991-1995, 1996-2000, 2001-2005, and 2006-2012). The effects of temperature on mortality were evaluated according to the occurrence of a heat wave and results were compared in the two cities. The effect of temperature on mortality was the greatest in 1991-1995 in Seoul; no significant change was observed in Busan. When we stratified the study period by heat wave status, the risk increase in mortality was 15.9% per 1℃ during years with a heat wave in Seoul, which was much higher than 0.31% increase observed during years without a heat wave. On the other hand, Busan showed a linear relationship between temperature and mortality and no significant difference between years with or without a heat wave. Variations in the relationship between temperature and mortality could be misunderstood if heat waves are not considered. Furthermore, heterogeneity was found in the modifying effect of heat waves on heat-related mortality in inland and coastal cities. The findings of this study help understand relations between temperature and mortality. PMID:27134490

  16. Long-term variability of heat waves in Argentina and recurrence probability of the severe 2008 heat wave in Buenos Aires

    Science.gov (United States)

    Rusticucci, Matilde; Kyselý, Jan; Almeira, Gustavo; Lhotka, Ondřej

    2016-05-01

    Heat waves are one of the main concerns related to the impacts of climate change, because their frequency and severity are projected to increase in a future climate. The objectives of this work are to study the long-term variability of heat waves over Argentina and to estimate recurrence probability of the most severe 2008 heat wave in Buenos Aires. We used three definitions of heat waves that were based on (1) daily maximum temperature above the 90th percentile (MaxTHW), (2) daily minimum temperature above the 90th percentile (MinTHW) and (3) both maximum and minimum temperatures above the corresponding 90th percentiles (EHW). The minimum length of a heat wave was 3 days, and the analysis was performed over the October-March period. Decadal values in Buenos Aires experienced clear increases in heat waves according to MinTHW and EHW, with the highest frequency for both in the 2001-2010 decade, but at other stations, combinations of different trends and decadal variability resulted in some cases in a decrease of extreme heat waves. In the north-western part of the country, a strong positive change in the last decade was found, mainly due to the increment in the persistence of MinTHW but also accompanied by increases in MaxTHW. In general, other stations show a clear positive trend in MinTHW and decadal variability in MaxTHW, with the largest EHW cases in the last decade. We also estimated recurrence probability of the longest and most severe heat wave in Buenos Aires (over 1909-2010, according to intensity measured by the cumulative excess of maximum daily temperature above the 90th percentile) that occurred from 3 to 14 November 2008, by means of simulations with a stochastic first-order autoregressive model. The recurrence probability of such long and severe heat wave is small in the present climate but it is likely to increase substantially in the near future even under a moderate warming trend.

  17. Alfvenic reacceleration of relativistic particles in galaxy clusters in the presence of secondary electrons and positrons

    OpenAIRE

    Brunetti, G.; P. Blasi(INAF Arcetri)

    2005-01-01

    In a previous paper (Brunetti et al. 2004) we presented the first self-consistent calculations of the time-dependent coupled equations for the electrons, hadrons and Alfv\\'en waves in the intracluster medium, which describe the stochastic acceleration of the charged particles and the corresponding spectral modification of the waves. Under viable assumptions, this system of mutually interacting components was shown to accurately describe several observational findings related to the radio halo...

  18. Nonresonant and stochastic heating of ions by low-frequency wave

    International Nuclear Information System (INIS)

    The present paper addresses the nonresonant and stochastic heating of minor ions by a low-frequency Alfvén wave in the solar wind. A new and whole physical mechanism that enables the heating of ions by a low-frequency parallel propagating wave with finite amplitude in a low beta plasma. The heating process has two stages: First, ions are picked up via low-frequency wave–ion nonresonant interaction and the ion energy gain depends on the ratio of the wave electric-field energy to background magnetic-field energy. Second, when the velocity approaches the threshold value, the stochastic heating is prominent. The stochastic heating of ions sustains until the average parallel speed is close to the wave velocity

  19. Phenomenology of Compressional Alfven Eigenmodes

    International Nuclear Information System (INIS)

    Coherent oscillations with frequency 0.3 (le) ω/ωci (le) 1, are seen in the National Spherical Torus Experiment [M. Ono, S.M. Kaye, Y-K.M. Peng, (and others), Nucl. Fusion 40, 557 (2000)]. This paper presents new data and analysis comparing characteristics of the observed modes to the model of compressional Alfven eigenmodes (CAE). The toroidal mode number has been measured and is typically between 7 < n < 9. The polarization of the modes, measured using an array of four Mirnov coils, is found to be compressional. The frequency scaling of the modes agrees with the predictions of a numerical 2-D code, but the detailed structure of the spectrum is not captured with the simple model. The fast ion distribution function, as calculated with the beam deposition code in TRANSP [R.V. Budny, Nucl. Fusion 34, 1247 (1994)], is shown to be qualitatively consistent with the constraints of the Doppler-shifted cyclotron resonance drive model. This model also predicts the observed scaling of the low frequency limit for CAE

  20. Simulation on heating of plasma in a magnetic field with electrostatic wave

    International Nuclear Information System (INIS)

    A uniform nonlinear resonant condition for interaction between electrostatic wave and charged particles in a uniform magnetic field is given by multi-scale expansion. It is verified by numerical simulation. It is shown that resonant heating can be produced by electrostatic wave with sub-harmonic frequency of the cyclotron. Moreover, it is shown that the heating efficiency does not increase with the amplitude of driving wave even if for the same frequency, which means there is an optimum combination of frequency and amplitude to get efficient heating. (authors)

  1. Recent changes in air temperature, heat waves occurrences, and atmospheric circulation in Northern Africa

    OpenAIRE

    Fontaine, B.; Janicot, Serge; Monerie, P. A.

    2013-01-01

    This study documents the time evolution of air temperature and heat waves occurrences over Northern Africa for the period 1979-2011. A significant warming (1 degrees-3 degrees C), appearing by the mid-1960s over Sahara and Sahel, is associated with higher/lesser frequency of warm/cold temperatures, as with longer duration and higher occurrences of heat waves. Heat waves episodes of at least 4 day duration have been examined after removing the long-term evolution. These episodes are associated...

  2. Numerical Anaysis on Heat Transfer Enhancement by Waves on Falling Liquid Film

    Institute of Scientific and Technical Information of China (English)

    AkioMiyara

    2000-01-01

    Numerical simulations have been carried out for two dimensional wavy falling liquid films on a vertical wall.The algorithm of the simulation is based on MAC method and schemes for interfacial boundary conditions are modifed.Small artificial perturbations given at the inflow boundary grow rapidly and then the amplitude of the waves approaches to developed waves.Effects of the disturbance frequency on the wave development behavior and heat transfer characteristics are especially investigated.For low frequency,a disturbance wave develops to a solitary wave consisted of a large amplitude roll wave and small amplitude capillary waves,Increasing the frequency,the wave amplitude decreases and the capillary wave disappears.For further high frequency,the disturbance amplitude reduces along down stream.The heat transfer coefficient is enhanced by the surface wave and has a maximum at a certain frequency,The streamlines and the temperature comtoure contours are shown for various frequency waves and the heat transfer enhancement mechanism is clarified.

  3. Direct electron heating by 60 MHz fast waves on DIII-D

    International Nuclear Information System (INIS)

    Efficient direct electron heating by fast waves has been observed on the DIII-D tokamak. A four strap antenna with (0,π,0,π) phasing launched up to 1.6 MW of fast wave power with |nparallel| ∼ 11. This |nparallel| is suitable for strong electron interaction in ohmic target plasmas (Te ≤ 2 keV). Ion cyclotron absorption was minimized by keeping the hydrogen fraction low (H = 8ΩD at 1T). The fast wave electron heating was weak for central electron temperatures below 1 keV, but improved substantially with increasing Te. Although linear theory predicts a strong inverse magnetic field scaling of the first pass absorption, the measured fast-wave heating efficiency was independent of magnetic field. Multiple pass absorption of the fast waves appears to be occurring since at 2.1 T nearly 100% efficient plasma heating is observed while the calculated first pass absorption is 6% to 8%. The central electron temperature during fast wave heating also increased with magnetic field. The improved electron heating at higher magnetic fields may be due in part to a peaking of the ohmic plasma current and the ohmic electron temperature profiles. Centrally peaked deposition profiles were measured by modulating the fast wave power at 10 Hz and observing the local electron temperature response across the plasma. 11 refs., 10 figs

  4. Benchmarking Fast-to-Alfven Mode Conversion in a Cold MHD Plasma

    CERN Document Server

    Cally, Paul S

    2011-01-01

    Alfv\\'en waves may be generated via mode conversion from fast magneto-acoustic waves near their reflection level in the solar atmosphere, with implications both for coronal oscillations and for active region helio-seismology. In active regions this reflection typically occurs high enough that the Alfv\\'en speed $a$ greatly exceeds the sound speed $c$, well above the $a=c$ level where the fast and slow modes interact. In order to focus on the fundamental characteristics of fast/Alfv\\'en conversion, stripped of unnecessary detail, it is therefore useful to freeze out the slow mode by adopting the gravitationally stratified cold MHD model $c\\to0$. This provides a benchmark for fast-to-Alfv\\'en mode conversion in more complex atmospheres. Assuming a uniform inclined magnetic field and an exponential Alfv\\'en speed profile with density scale height $h$, the Alfv\\'en conversion coefficient depends on three variables only; the dimensionless transverse-to-the-stratification wavenumber $\\kappa=kh$, the magnetic field ...

  5. Characteristics of ion Bernstein wave heating in JIPPT-II-U tokamak

    International Nuclear Information System (INIS)

    Using a transport code combined with an ion Bernstein wave tokamak ray tracing code, a modelling code for the ion Bernstein wave heating has been developed. Using this code, the ion Bernstein wave heating experiment on the JIPPT-II-U tokamak has been analyzed. It is assumed that the resonance layer is formed by the third harmonic of deuterium-like ions, such as fully ionized carbon, and oxygen ions near the plasma center. For wave absorption mechanisms, electron Landau damping, ion cyclotron harmonic damping, and collisional damping are considered. The characteristics of the ion Bernstein wave heating experiment, such as the ion temperature increase, the strong dependence of the quality factor on the magnetic field strength, and the dependence of the ion temperature increment on the input power, are well reproduced

  6. Characteristics of ion Bernstein wave heating in JIPPT-II-U tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Okamoto, M.; Ono, M.

    1985-11-01

    Using a transport code combined with an ion Bernstein wave tokamak ray tracing code, a modelling code for the ion Bernstein wave heating has been developed. Using this code, the ion Bernstein wave heating experiment on the JIPPT-II-U tokamak has been analyzed. It is assumed that the resonance layer is formed by the third harmonic of deuterium-like ions, such as fully ionized carbon, and oxygen ions near the plasma center. For wave absorption mechanisms, electron Landau damping, ion cyclotron harmonic damping, and collisional damping are considered. The characteristics of the ion Bernstein wave heating experiment, such as the ion temperature increase, the strong dependence of the quality factor on the magnetic field strength, and the dependence of the ion temperature increment on the input power, are well reproduced.

  7. Role of soil moisture versus recent climate change for the 2010 heat wave in western Russia

    Science.gov (United States)

    Hauser, Mathias; Orth, René; Seneviratne, Sonia I.

    2016-03-01

    The severe 2010 heat wave in western Russia was found to be influenced by anthropogenic climate change. Additionally, soil moisture-temperature feedbacks were deemed important for the buildup of the exceptionally high temperatures. We quantify the relative role of both factors by applying the probabilistic event attribution framework and analyze ensemble simulations to distinguish the effect of climate change and the 2010 soil moisture conditions for annual maximum temperatures. The dry 2010 soil moisture alone has increased the risk of a severe heat wave in western Russia sixfold, while climate change from 1960 to 2000 has approximately tripled it. The combined effect of climate change and 2010 soil moisture yields a 13 times higher heat wave risk. We conclude that internal climate variability causing the dry 2010 soil moisture conditions formed a necessary basis for the extreme heat wave.

  8. Mapping heat wave risk in the UK: Proactive planning for the 2050s

    Science.gov (United States)

    Oven, Katie; Reaney, Sim; Ohlemüller, Ralf; Nodwell, Sarah; Curtis, Sarah; Riva, Mylène; Dunn, Christine; Val, Dimitri; Burkhard, Roland

    2010-05-01

    Climate change projections suggest an increased frequency of heat waves in the UK over the coming decades. Such extreme events pose a serious threat to human health and are likely to impact upon health and social care systems and the infrastructures supporting them. This stress will result from both increased demands upon healthcare services and the ability of the infrastructure to cope, such as sufficient climate control in hospitals. Certain sectors of the population, such as older people, have an increased susceptibility to heat waves and hence are the focus of this research. There is no universal definition of a heat wave, reflecting the acclimatisation of a population. Based on a review of the literature, this research therefore sets out a series of working definitions of a heat wave in the UK context from a human health perspective. Drawing on these definitions, the UK heat wave hazard was mapped for the 2050s (2040-2069) using daily minimum and maximum temperature data derived from the UKCP09 Weather Generator at 50 km resolution. The analysis was undertaken for the three different greenhouse gas emissions scenarios within UKCP09 (low, medium and high). Hot spots of increased heat wave risk were identified and comparisons made between the various model outputs. These data were then combined with demographic forecasts for the 2050s enabling the identification of areas with an ageing population. Results are presented showing the scale of the projected change in heat wave risk across the UK and the location of older people. These results will be used in proactive planning to help policymakers and practitioners respond more appropriately to the needs of vulnerable populations in the coming decades. Key words: climate change; heat wave; risk mapping; vulnerability; risk reduction.

  9. Heat precursor of the blast wave in weakly ionized plasma

    International Nuclear Information System (INIS)

    Electron temperature distributions in weakly ionized plasma are numerically calculated for the blast-type shock waves. Comparison with experimental data obtained in glow discharge in Ar, as well as in shock waves with constant pressure in HF low-pressure discharge plasma in air is made

  10. A protocol to assess insect resistance to heat waves, applied to bumblebees (Bombus Latreille, 1802.

    Directory of Open Access Journals (Sweden)

    Baptiste Martinet

    Full Text Available Insect decline results from numerous interacting factors including climate change. One of the major phenomena related to climate change is the increase of the frequency of extreme events such as heat waves. Since heat waves are suspected to dramatically increase insect mortality, there is an urgent need to assess their potential impact. Here, we determined and compared the resistance to heat waves of insects under hyperthermic stress through their time before heat stupor (THS when they are exposed to an extreme temperature (40°C. For this, we used a new experimental standardised device available in the field or in locations close to the field collecting sites. We applied this approach on different Arctic, Boreo-Alpine and Widespread bumblebee species in order to predict consequences of heat waves. Our results show a heat resistance gradient: the heat stress resistance of species with a centred arctic distribution is weaker than the heat resistance of the Boreo-Alpine species with a larger distribution which is itself lower than the heat stress resistance of the ubiquitous species.

  11. Heat wave generates questions about Ontario's generation capacity

    International Nuclear Information System (INIS)

    Concerns regarding Ontario's power generation capacity were raised following a major blackout which occurred in August 2003. Power demand reached 26,170 MW during the weeks leading to the blackout, forcing the Independent Electricity System Operator (IESO) to ask residents to reduce electricity use during the day. The grid operator had also issued a forecast that Toronto could face rolling blackouts during times of heavy power demand. Ontario power consumption records were set in June and July of 2003 due to a heat wave, with hourly demand exceeding 25,000 MW on 53 occasions. Ontario was forced to import up to 3,400 MW (13 per cent of its power needs) from neighbouring provinces and the United States. During that period, the price of power had risen sharply to over 30 cents a kilowatt hour, although household consumers were still charged in the 5 to 10 cent range per kilowatt hour. However, it was noted that taxpayers will eventually bear the cost of importing power. The IESO noted that importing electricity is cheaper than the generation available in Ontario and that it is more economical to import, based on the market clearing price of all generators. In 2004, the IESO purchased 6 per cent of their electricity from the United States. That figure is expected to increase for 2005. Ontario generators produced 26.9 million MWh more in the summer of 2005 than during the same period in 2004 to meet electricity demand levels. It was noted that although importing power presently meets peak demand, the IESO agrees there is a need for new generation within Ontario. In addition to restarting Ontario's Pickering and Bruce nuclear facilities, more than 3,300 MW of new gas-fired generation is under construction or approved, and more than 9,000 MW are in various stages of approval. This paper discussed the effect of high energy costs on industry and Ontario's ability to meet future electricity demand in comparison to neighbouring jurisdictions. Issues regarding grid maintenance

  12. Whistler mode waves and the electron heat flux in the solar wind: cluster observations

    International Nuclear Information System (INIS)

    The nature of the magnetic field fluctuations in the solar wind between the ion and electron scales is still under debate. Using the Cluster/STAFF instrument, we make a survey of the power spectral density and of the polarization of these fluctuations at frequencies f in [1, 400] Hz, during five years (2001-2005), when Cluster was in the free solar wind. In ∼10% of the selected data, we observe narrowband, right-handed, circularly polarized fluctuations, with wave vectors quasi-parallel to the mean magnetic field, superimposed on the spectrum of the permanent background turbulence. We interpret these coherent fluctuations as whistler mode waves. The lifetime of these waves varies between a few seconds and several hours. Here, we present, for the first time, an analysis of long-lived whistler waves, i.e., lasting more than five minutes. We find several necessary (but not sufficient) conditions for the observation of whistler waves, mainly a low level of background turbulence, a slow wind, a relatively large electron heat flux, and a low electron collision frequency. When the electron parallel beta factor β e∥ is larger than 3, the whistler waves are seen along the heat flux threshold of the whistler heat flux instability. The presence of such whistler waves confirms that the whistler heat flux instability contributes to the regulation of the solar wind heat flux, at least for β e∥ ≥ 3, in slow wind at 1 AU.

  13. Quantification and assessment of heat and cold waves in Novi Sad, Northern Serbia

    Science.gov (United States)

    Basarin, Biljana; Lukić, Tin; Matzarakis, Andreas

    2016-01-01

    Physiologically equivalent temperature (PET) has been applied to the analysis of heat and cold waves and human thermal conditions in Novi Sad, Serbia. A series of daily minimum and maximum air temperature, relative humidity, wind, and cloud cover was used to calculate PET for the investigated period 1949-2012. The heat and cold wave analysis was carried out on days with PET values exceeding defined thresholds. Additionally, the acclimatization approach was introduced to evaluate human adaptation to interannual thermal perception. Trend analysis has revealed the presence of increasing trend in summer PET anomalies, number of days above defined threshold, number of heat waves, and average duration of heat waves per year since 1981. Moreover, winter PET anomaly as well as the number of days below certain threshold and number of cold waves per year until 1980 was decreasing, but the decrease was not statistically significant. The highest number of heat waves during summer was registered in the last two decades, but also in the first decade of the investigated period. On the other hand, the number of cold waves during six decades is quite similar and the differences are very small.

  14. Damping of kinetic Alfven eigenmodes in tokamak plasmas

    International Nuclear Information System (INIS)

    The ability to predict the stability of fast-particle-driven Alfven eigenmodes in burning fusion plasmas requires a detailed understanding of the dissipative mechanisms that damp these modes. In order to address this question, the linear gyro-kinetic, electromagnetic code LIGKA is employed to investigate their behaviour in realistic tokamak geometry. LIGKA is based on an eigenvalue formulation and self-consistently calculates the coupling of large-scale MHD modes to gyro-radius scale length kinetic Alfven waves. It uses the drift-kinetic HAGIS code to accurately describe the unperturbed particle orbits in general geometry. In addition, a newly developed antenna-like version of LIGKA allows for a frequency scan, analogous to an external antenna. With these tools the properties of the kinetically modified TAE in or near the gap (KTAE, radiative damping or 'tunnelling') and its coupling to the continuum close to the edge are numerically analysed. The results are compared with previous calculations based on fluid and other gyro-kinetic models. Also first linear calculations on cascade modes are presented. (author)

  15. The 1994 heat wave in South Korea: mortality impacts and recurrence probability in a changing climate

    Science.gov (United States)

    Kysely, J.; Kim, J.

    2010-03-01

    The study deals with mortality impacts of the July-August 1994 heat wave in the population of South Korea, including the megacity of Seoul (with the population exceeding 10 million for the city and 20 million for the metropolitan area), and estimates recurrence probability of the heat wave in a changing climate in terms of simulations of daily temperature series with a stochastic model. The 1994 heat wave is found exceptional with respect to both climatological characteristics and the mortality effects: significantly elevated mortality occurred in all population groups, including children up to 14 years of age, and the total death toll exceeded 3000 in the Korean population, which ranks the 1994 heat wave among the worst weather-related disasters in East Asia. The estimate represents net excess mortality as no mortality displacement effect appeared. A comparison with other documented natural disasters shows that the death toll of the heat wave was much higher than those of the most disastrous floodings and typhoons over Korean Peninsula in the 20th century. The mortality response was stronger in males than females although males are found to be less vulnerable during average heat waves. A climatological analysis reveals that the July-August 1994 heat wave might be considered an extremely rare event with a return period in the order of hundreds of years if stationarity of temperature time series is assumed. However, under a more realistic assumption of gradual warming related to climate change, recurrence probability of an event analogous to the 1994 heat wave sharply rises for near-future time horizons. If warming of 0.04°C/year is assumed over 2001-2060, the recurrence interval of a very long spell of days with temperature exceeding a high threshold (as in the 1994 heat wave) is estimated to decrease to around 40 (10) years in the 2021-2030 (2041-2050) decade. This emphasizes the need for setting up an efficient heat-watch-warning system in this area in order to

  16. Nonlinear traveling waves in a two-layer system with heat release/consumption at the interface

    Science.gov (United States)

    Simanovskii, Ilya B.; Viviani, Antonio; Dubois, Frank; Legros, Jean-Claude

    2016-06-01

    The influence of an interfacial heat release and heat consumption on nonlinear convective flows, developed under the joint action of buoyant and thermocapillary effects in a laterally heated two-layer system with periodic boundary conditions, is investigated. Regimes of traveling waves and modulated traveling waves have been obtained. It is found that rather intensive heat sinks at the interface can lead to the change of the direction of the waves' propagation.

  17. Decreased impacts of the 2003 heat waves on mortality in the Czech Republic: an improved response?

    Czech Academy of Sciences Publication Activity Database

    Kyselý, Jan; Kříž, B.

    2008-01-01

    Roč. 52, č. 8 (2008), s. 733-745. ISSN 0020-7128 R&D Projects: GA ČR GA205/07/1254 Institutional research plan: CEZ:AV0Z30420517 Keywords : heat wave * heat-related mortality * air temperature * central Europe * environment Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 2.084, year: 2008

  18. A Comprehensive Comparison between Wave Propagation and Heat Distribution via Analytical Solutions and Computer Simulations

    Directory of Open Access Journals (Sweden)

    Ramin Shamshiri

    2014-01-01

    Full Text Available Wave propagation and heat distribution are both governed by second order linear constant coefficient partial differential equations, however their solutions yields very different properties. This study presents a comprehensive comparison between hyperbolic wave equation and parabolic heat equation. Issues such as conservation of wave profile versus averaging, transporting information, finite versus infinite speed propagation, time reversibility versus irreversibility and propagation of singularities versus instantaneous smoothing have been addressed and followed by examples and graphical evidences from computer simulations to support the arguments.

  19. Generation of whistler waves by continuous HF heating of the upper ionosphere

    Science.gov (United States)

    Vartanyan, A.; Milikh, G. M.; Eliasson, B. E.; Sharma, A.; Chang, C.; Parrot, M.; Papadopoulos, K.

    2013-12-01

    We report observations of VLF waves by the DEMETER satellite overflying the HAARP facility during ionospheric heating experiments. The detected VLF waves were in the range 8-17 kHz and coincided with times of continuous heating. The experiments indicate whistler generation due to conversion of artificial lower hybrid waves to whistlers on small scale field-aligned plasma density striations. The observations are compared with theoretical models, taking into account both linear and nonlinear processes. Implications of the mode conversion technique on VLF generation with subsequent injection into the radiation belts to trigger particle precipitation are discussed.

  20. An Efficient Approximation of the Coronal Heating Rate for Use in Global Sun-Heliosphere Simulations

    OpenAIRE

    Cranmer, Steven R.

    2009-01-01

    The origins of the hot solar corona and the supersonically expanding solar wind are still the subject of debate. A key obstacle in the way of producing realistic simulations of the Sun-heliosphere system is the lack of a physically motivated way of specifying the coronal heating rate. Recent one-dimensional models have been found to reproduce many observed features of the solar wind by assuming the energy comes from Alfven waves that are partially reflected, then dissipated by magnetohydrodyn...

  1. Wave-mean flow interaction and its relationship with the atmospheric energy cycle with diabatic heating

    Institute of Scientific and Technical Information of China (English)

    DUAN; Anmin

    2005-01-01

    Based on the traditional theory of wave mean flow interaction, an improved quasi-geostrophic Eliassen-Palm flux with diabatic heating included is deduced. It is shown that there exists an intrinsic relation between the atmospheric energy cycle derived by Lorenz and the wave energy transfer derived by Eliassen and Palm. From this relation it becomes clear that the energy propagation process of large-scale stationary wave is indeed a part of Lorenz energy cycle, and the energy transform from mean flow to wave equals the global mass integral of the divergence of local wave energy flux or the global integral of local wave energy. The diagnostic results by using NCEP/NCAR reanalysis data suggest that the classical adiabatic Eliassen-Palm flux relation can present only the wintertime wave energy transformation. For other seasons, however, the diabatic effect must be taken into account.

  2. Exploration of High Harmonic Fast Wave Heating on the National Spherical Torus Experiment

    International Nuclear Information System (INIS)

    High Harmonic Fast Wave (HHFW) heating has been proposed as a particularly attractive means for plasma heating and current drive in the high-beta plasmas that are achievable in spherical torus (ST) devices. The National Spherical Torus Experiment (NSTX) [Ono, M., Kaye, S.M., Neumeyer, S., et al., Proceedings, 18th IEEE/NPSS Symposium on Fusion Engineering, Albuquerque, 1999, (IEEE, Piscataway, NJ (1999), p. 53.)] is such a device. An radio-frequency (rf) heating system has been installed on NSTX to explore the physics of HHFW heating, current drive via rf waves and for use as a tool to demonstrate the attractiveness of the ST concept as a fusion device. To date, experiments have demonstrated many of the theoretical predictions for HHFW. In particular, strong wave absorption on electrons over a wide range of plasma parameters and wave parallel phase velocities, wave acceleration of energetic ions, and indications of current drive for directed wave spectra have been observed. In addition HHFW heating has been used to explore the energy transport properties of NSTX plasmas, to create H-mode (high-confinement mode) discharges with a large fraction of bootstrap current and to control the plasma current profile during the early stages of the discharge

  3. A Global Wave-Driven MHD Solar Model with a Unified Treatment of Open and Closed Magnetic Field Topologies

    CERN Document Server

    Oran, R; Landi, E; Jin, M; Sokolov, I V; Gombosi, T I

    2013-01-01

    We describe, analyze and validate the recently developed Alfv\\'en Wave Solar Model (AWSoM), a 3D global model starting from the top of the chromosphere and extending into interplanetary space (up to 1-2 AU). This model solves the extended two temperature magnetohydrodynamics equations coupled to a wave kinetic equation for low frequency Alfv\\'en waves. In this picture, heating and acceleration of the plasma are due to wave dissipation and wave pressure gradients, respectively. The dissipation process is described by a fully developed turbulent cascade of counter-propagating waves. We adopt a unified approach for calculating the wave dissipation in both open and closed magnetic field lines, allowing for a self-consistent treatment of any magnetic topology. Wave dissipation is the only heating mechanism assumed in the model, and no geometric heating functions are invoked. Electron heat conduction and radiative cooling are also included. We demonstrate that the large-scale, steady-state (in the co-rotating frame...

  4. Spatial and temporal characteristics of heat waves over Central Europe in an ensemble of regional climate model simulations

    Science.gov (United States)

    Lhotka, Ondřej; Kyselý, Jan

    2015-11-01

    The study examines the capability of regional climate models (RCMs) to reproduce spatial and temporal characteristics of severe Central European heat waves. We analysed an ensemble of seven RCM simulations driven by the ERA-40 reanalysis over the 1961-2000 period, in comparison to observed data from the E-OBS gridded dataset. Heat waves were defined based on regionally significant excesses above the model-specific 95 % quantile of summer daily maximum air temperature distribution and their severity was described using the extremity index. The multi-model mean reflected the observed characteristics of heat waves quite well, but considerable differences were found among the individual RCMs. The RCMs had a tendency to simulate too many heat waves that were shorter but their temperature peak was more pronounced on average compared to E-OBS. Deficiencies were found also in reproducing interannual and interdecadal variability of heat waves. Using as an example the most severe Central European heat wave that occurred in 1994, we demonstrate that its magnitude was underestimated in all RCMs and that this bias was linked to overestimation of precipitation during and before the heat wave. By contrast, a simulated precipitation deficit during summer 1967 in the majority of RCMs contributed to an "erroneous" heat wave. This shows that land-atmosphere coupling is crucial for developing severe heat waves and its proper reproduction in climate models is essential for obtaining credible scenarios of future heat waves.

  5. Urban and rural mortality rates during heat waves in Berlin and Brandenburg, Germany

    International Nuclear Information System (INIS)

    In large cities such as Berlin, human mortality rates increase during intense heat waves. Analysis of relevant data from north-eastern Germany revealed that, during the heat waves that occurred between 1990 and 2006, health risks were higher for older people in both rural and urban areas, but that, during the two main heat waves within that 17-year period of time, the highest mortality rates were from the city of Berlin, and in particular from its most densely built-up districts. Adaptation measures will need to be developed, particularly within urban areas, in order to cope with the expected future intensification of heat waves due to global climate change. - Highlights: → Periods of heat stress enhance mortality rates in Berlin and Brandenburg. → Heat-related mortality is an urban as well as a rural problem. → During extreme events highest mortality rates can be found in the city centre. → Mortality rates correlate well with the distribution of sealed surfaces. → Health risks are higher for older than for younger people. - During periods of severe heat stress the pattern of mortality rates in Berlin and Brandenburg was found to correlate well with the distribution of sealed surfaces.

  6. Alfven solitons in the coupled derivative nonlinear Schroedinger system with symbolic computation

    International Nuclear Information System (INIS)

    The propagation of nonlinear Alfven waves in magnetized plasmas with right and left circular polarizations is governed by the coupled derivative nonlinear Schroedinger (CDNLS) system. The integrability of this system is indicated by the existence of two gauge-equivalent Lax pairs and infinitely many independent conservation laws. With symbolic computation, the analytic one- and two-soliton solutions are obtained via the Hirota bilinear method. The propagation characteristics of the Alfven waves are discussed through qualitative analysis. The collision dynamics of the CDNLS solitons is found to be characterized by the invariance of the soliton velocities and widths, parameter-dependent changes of the soliton amplitudes and conservation of the total energy of right- and left-polarized components. The parametric condition for the amplitude-preserving collision occurring in each component is explicitly given.

  7. Climate change and heat waves in Paris and London metropolitan areas

    Science.gov (United States)

    Dousset, B.

    2010-12-01

    Summer warming trends in Western and Central Europe and in Mediterranean regions are increasing the incidence, intensity, and duration of heat waves. Those extreme events are especially deadly in large cities, owing to high population densities, surface characteristics, heat island effects, anthropogenic heat and pollutants. In August 2003, a persistent anticyclone over Western Europe generated a heat wave of exceptional strength and duration with an estimated death toll of 70,000, including 4678 in the Paris region. A series of NOAA-AVHRR satellite thermal images over the Paris and London metropolitan areas, were used to analyze Land Surface Temperature (LST) and its related mortality. In the Paris region, LSTs were merged with land use and cover data to identify risk areas, and thermal indicators were produced at the addresses of ~ 500 elderly people to assess diurnal heat exposure. Results indicate: (i) contrasting night time and daytime heat island patterns related to land use and surface characteristics; (ii) the relation between night-time heat islands and heat waves intensity; (iii) the impact of elevated minimal temperatures on excess mortality, with a 0.5 °C increase doubling the risk of death, (in the temperature range of the heatwave); iv) the correlation between the spatial distribution of highest night-time LSTs and that of highest mortality ratios; and v) the significant impact of urban parks in the partitioning between latent and sensible surface heat fluxes, despite a prior warm and dry spring. Near-real time satellite monitoring of heat waves in urban areas improve our understanding of the LST processes and spatial variability, and of the related heat stress and mortality. These observations provide criteria for warning systems, contingency policies and planning, and climate adaptation and mitigation strategies.

  8. Surface Bloch waves mediated heat transfer between two photonic crystals

    OpenAIRE

    Ben-Abdallah, Philippe; Joulain, Karl; Pryamikov, Andrey

    2010-01-01

    submitted to Applied Physics Letters We theoretically investigate the non-radiative heat transfer between two photonic crystals separated by a small gap in non-equilibrium thermal situation. We predict that the surface Bloch states coupling supported by these media can make heat exchanges larger than those measured at the same separation distance between two massive homogeneous materials made with the elementary components of photonic crystals. These results could find broad applications i...

  9. Global Alfven eigenmodes stability in thermonuclear tokamak plasmas

    International Nuclear Information System (INIS)

    Relying on the good agreement observed between the gyrokinetic PENN model and the low n damping measurements from JET, the stability of Alfven eigenmodes (AE) is here predicted for reactor relevant conditions. Full non-local wave-particle power transfers are computed for the α-particles in an ITER reference equilibrium, showing that low n ≅ 2 modes are strongly damped and intermediate n ≅ 12 with a global radial extension are stable with a damping rate γ/ω ≅ 0.02. Even though an excitation of α-particle driven instabilities remains in principle possible, this study suggests that realistic operation scenarii exist where all the AEs of global character are stable. (author)

  10. MHD-Vlasov simulation of the toroidal Alfven eigenmode

    International Nuclear Information System (INIS)

    A new simulation method has been developed to investigate the excitation and saturation processes of toroidal Alfven eigenmodes (TAE modes). The background plasma is described by a full-MHD fluid model, while the kinetic evolution of energetic alpha particles is followed by the drift kinetic equation. The magnetic fluctuation of n = 2 mode develops and saturates at the level of 1.8x10-3 of the equilibrium field when the initial beta of alpha particles is 2% at the magnetic axis. After saturation, the TAE mode amplitude shows an oscillatory behavior with a frequency corresponding to the bounce frequency of the alpha particles trapped by the TEA mode. The decrease of the power transfer rate from the alpha particles to the TAE mode, which is due to the trapped particle effect of a finite-amplitude wave, causes the saturation. From the linear growth rate the saturation level can be estimated. (author)

  11. Nonlinear competition between the whistler and Alfven firehoses. Journal of Geophysical Research, 106, 13,215, 2001

    Czech Academy of Sciences Publication Activity Database

    Hellinger, Petr; Matsumoto, H.

    2001-01-01

    Roč. 106, - (2001), s. 13,215-13,224. ISSN 0148-0227 R&D Projects: GA AV ČR IAB3042106 Institutional research plan: CEZ:AV0Z3042911 Keywords : instability * whistler * Alfven wave Subject RIV: BE - Theoretical Physics Impact factor: 2.609, year: 2001

  12. Heat-related mortality in India: excess all-cause mortality associated with the 2010 Ahmedabad heat wave.

    Directory of Open Access Journals (Sweden)

    Gulrez Shah Azhar

    Full Text Available INTRODUCTION: In the recent past, spells of extreme heat associated with appreciable mortality have been documented in developed countries, including North America and Europe. However, far fewer research reports are available from developing countries or specific cities in South Asia. In May 2010, Ahmedabad, India, faced a heat wave where the temperatures reached a high of 46.8 °C with an apparent increase in mortality. The purpose of this study is to characterize the heat wave impact and assess the associated excess mortality. METHODS: We conducted an analysis of all-cause mortality associated with a May 2010 heat wave in Ahmedabad, Gujarat, India, to determine whether extreme heat leads to excess mortality. Counts of all-cause deaths from May 1-31, 2010 were compared with the mean of counts from temporally matched periods in May 2009 and 2011 to calculate excess mortality. Other analyses included a 7-day moving average, mortality rate ratio analysis, and relationship between daily maximum temperature and daily all-cause death counts over the entire year of 2010, using month-wise correlations. RESULTS: The May 2010 heat wave was associated with significant excess all-cause mortality. 4,462 all-cause deaths occurred, comprising an excess of 1,344 all-cause deaths, an estimated 43.1% increase when compared to the reference period (3,118 deaths. In monthly pair-wise comparisons for 2010, we found high correlations between mortality and daily maximum temperature during the locally hottest "summer" months of April (r = 0.69, p<0.001, May (r = 0.77, p<0.001, and June (r = 0.39, p<0.05. During a period of more intense heat (May 19-25, 2010, mortality rate ratios were 1.76 [95% CI 1.67-1.83, p<0.001] and 2.12 [95% CI 2.03-2.21] applying reference periods (May 12-18, 2010 from various years. CONCLUSION: The May 2010 heat wave in Ahmedabad, Gujarat, India had a substantial effect on all-cause excess mortality, even in this city where hot temperatures

  13. Anisotropic Alfven-ballooning modes in the Earth's magnetosphere

    International Nuclear Information System (INIS)

    We have carried out a theoretical analysis of the stability and parallel structure of coupled shear-Alfven and slow-magnetosonic waves in the Earth's inner magnetosphere including effects of finite anisotropic plasma pressure. Multiscale perturbation analysis of the anisotropic Grad-Shafranov equation yields an approximate self-consistent magnetohydrodynamic (MHD) equilibrium. This MHD equilibrium is used in the numerical solution of a set of eigenmode equations which describe the field line eigenfrequency, linear stability, and parallel eigenmode structure. We call these modes anisotropic Alfven-ballooning modes. The main results are: The field line eigenfrequency can be significantly lowered by finite pressure effects. The parallel mode structure of the transverse wave components is fairly insensitive to changes in the plasma pressure but the compressional magnetic component can become highly peaked near the magnetic equator due to increased pressure, especially when P perpendicular > P parallel. For the isotropic case ballooning instability can occur when the ratio of the plasma pressure to the magnetic pressure, exceeds a critical value βoB ∼ 3.5 at the equator. Compared to the isotropic case the critical beta value is lowered by anisotropy, either due to decreased field-line-bending stabilization when P parallel > P perpendicular, or due to increased ballooning-mirror destabilization when P perpendicular > P parallel. We use a ''β-6 stability diagram'' to display the regions of instability with respect to the equatorial values of the parameters bar β and δ, where bar β = (1/3)(βparallel + 2 β perpendicular) is an average beta value and δ = 1 - P parallel/P perpendicular is a measure of the plasma anisotropy

  14. Supersonic wave detection method for leakage of water from heat exchanger

    International Nuclear Information System (INIS)

    The present invention provides a method of detecting leakage of water from a heat exchanger such as in an FBR type reactor by using supersonic waves. Namely, the inside of the body of the heat exchanger is divided circumferentially into a plurality of chambers. A plurality of transmitting/receiving sensors are disposed on the outer side of the body in the circumferential direction corresponding to the plurality of chambers. They are disposed in a plurality of stages in the longitudinal direction of the body. Burst wave-like supersonic waves having the same frequency are successively transmitted from the transmitting portion of each of the transmitting/receiving sensors in the circumferential direction and then the supersonic waves are received by the received portions, and this operation is repeated. After the operation is completed for every transmitting/receiving portions, the operation is repeated by using burst-like supersonic waves of different frequencies. The burst-like supersonic waves are thus allowed to pass through steam bubbles generated by jetting high pressure steams leaked from liquid sodium flowing in the body of the heat exchanger, and the decayed burst-like supersonic waves are received by any of the transmitting/receiving sensors to detect leakage of water. The method of the present invention has high sensitivity irrespective of the scale of the leakage. (I.S.)

  15. The Potential for Ambient Plasma Wave Propulsion

    Science.gov (United States)

    Gilland, James H.; Williams, George J.

    2016-01-01

    frequencies below the ion cyclotron frequency. They have been observed in both laboratory and astrophysical settings. On Earth, they are being investigated as a possible means for plasma heating, current drive, and momentum addition in magnetic confinement fusion systems. In addition, Alfven waves have been proposed as a mechanism for acceleration of the solar wind away from the sun.

  16. The 2003 heat wave in France: dangerous climate change here and now.

    Science.gov (United States)

    Poumadère, Marc; Mays, Claire; Le Mer, Sophie; Blong, Russell

    2005-12-01

    In an analysis of the French episode of heat wave in 2003, this article highlights how heat wave dangers result from the intricate association of natural and social factors. Unusually high temperatures, as well as socioeconomic vulnerability, along with social attenuation of hazards, in a general context where the anthropogenic contribution to climate change is becoming more plausible, led to an excess of 14,947 deaths in France, between August 4 and 18, 2003. The greatest increase in mortality was due to causes directly attributable to heat: dehydration, hyperthermia, heat stroke. In addition to age and gender, combinatorial factors included preexisting disease, medication, urban residence, isolation, poverty, and, probably, air pollution. Although diversely impacted or reported, many parts of Europe suffered human and other losses, such as farming and forestry through drought and fires. Summer 2003 was the hottest in Europe since 1500, very likely due in part to anthropogenic climate change. The French experience confirms research establishing that heat waves are a major mortal risk, number one among so-called natural hazards in postindustrial societies. Yet France had no policy in place, as if dangerous climate were restricted to a distant or uncertain future of climate change, or to preindustrial countries. We analyze the heat wave's profile as a strongly attenuated risk in the French context, as well as the causes and the effects of its sudden shift into amplification. Research and preparedness needs are highlighted. PMID:16506977

  17. Power Deposition of Ion Bernstein Wave Heating on the HT-7 Tokamak

    Institute of Scientific and Technical Information of China (English)

    BAO Yi; LI Jian-Gang; ZHAO Yan-Ping; CUI Ning-Zhuo

    2001-01-01

    Effcient direct heating of electrons by ion Bernstein waves has been obtained on the HT-7 tokamak. Off-axis heating, which is considered to be the result of electron Landau damping, was observed and studied by means of soft x-ray imaging. The measured power deposition was found to be independent of magnetic field through scanning the toroidal field from 1.5 to 1.7 T, in contrast to the ion heating results. It is suggested that the electron Landau damping is dominant in this heating regime.

  18. Stochastic properties of the plasma wave heating map

    International Nuclear Information System (INIS)

    Diffusion coefficient for stochastic ion motion in a lower hybrid wave is derived analytically by use of the characteristic function method. The renormalization calculation is carried out successfully to account for effects of the higher order correlation. Numerical observation of the diffusion process confirms the expectation that the renormalized diffusion coefficient describes correctly the stochastic properties of the systems even in the region of the small stochastic parameter, except where the accelerator modes manifest their influence upon the chaotic orbits. (author)

  19. An Estimate of Chromospheric Heating by Acoustic Waves

    Czech Academy of Sciences Publication Activity Database

    Sobotka, Michal; Švanda, Michal; Jurčák, Jan; Heinzel, Petr; Del Moro, D.; Berrilli, F.

    2014-01-01

    Roč. 38, č. 1 (2014), s. 53-58. ISSN 1845-8319 R&D Projects: GA ČR(CZ) GA14-04338S; GA ČR GPP209/12/P568; GA ČR GAP209/12/0287 Institutional support: RVO:67985815 Keywords : Sun * chromosphere * heating Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  20. Stochastic ion heating by an electrostatic wave in a sheared magnetic field

    International Nuclear Information System (INIS)

    The hot ion tail in the ion velocity distribution observed in lower-hybrid heating experiments has motivated lately a considerable amount of research interest in the mechanism responsible for its formation. Special attention was given to the possibility that stochastic acceleration of ions due to electrostatic waves propagating in the plasma may play an important role in this unexpected and unwanted strong heating of a selective part of the ion population. Considering r.f. electrostatic waves propagating in the plasma perpendicularly to the homogeneous magnetic field, Fukuyama et al., and Karney and Bers have demonstrated the possibility of stochastic ion heating due to nonlinear resonances between the motion in the electrostatic wave and cyclotron oscillations

  1. Long-term variability of heat waves in Argentina and recurrence probability of the severe 2008 heat wave in Buenos Aires

    Czech Academy of Sciences Publication Activity Database

    Rusticucci, M.; Kyselý, Jan; Almeira, G.; Lhotka, Ondřej

    2016-01-01

    Roč. 124, č. 3 (2016), s. 679-689. ISSN 0177-798X R&D Projects: GA MŠk 7AMB15AR001 Institutional support: RVO:68378289 Keywords : heat waves * long-term variability * climate extremes Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 2.015, year: 2014 http://link.springer.com/article/10.1007%2Fs00704-015-1445-7

  2. Variation of wave velocity and porosity of sandstone after high temperature heating

    Science.gov (United States)

    Sun, Qiang; Zhang, ·Weiqiang; Su, Tianming; Zhu, Shuyun

    2016-05-01

    This paper reports the variations of mass, porosity, and wave velocity of sandstone after high temperature heating. The range of temperature to which the sandstone specimens have been exposed is 25-850°C, in a heating furnace. It has been shown that below 300°C, porosity and wave velocity change very little. Above 300°C, there is a rapid increase in porosity, but the wave velocity decreases significantly. The results of thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC) and mercury intrusion porosimetry (MIP) suggest that a series of changes occurred between 400 and 600°C in sandstone could be responsible for the different patterns of variation in porosity and wave velocity.

  3. The Characteristic of Heat Wave Effects on Coronary Heart Disease Mortality in Beijing, China: A Time Series Study

    OpenAIRE

    Tian, Zhaoxing; Li, Shanshan; Zhang, Jinliang; Guo, Yuming

    2013-01-01

    Background There is limited evidence for the impacts of heat waves on coronary heart disease (CHD) mortality in Beijing, capital city of China. Objectives We aimed to find a best heat wave definition for CHD mortality; and explore the characteristic of heat wave effects on CHD in Beijing, China. Methods We obtained daily data on weather and CHD mortality in Beijing for years 2000–2011. A quasi-Poisson regression model was used to assess the short-term impact of heat waves on CHD mortality in ...

  4. Syndromic surveillance and heat wave morbidity: a pilot study based on emergency departments in France

    Directory of Open Access Journals (Sweden)

    Filleul Laurent

    2009-02-01

    Full Text Available Abstract Background The health impacts of heat waves are serious and have prompted the development of heat wave response plans. Even when they are efficient, these plans are developed to limit the health effects of heat waves. This study was designed to determine relevant indicators related to health effects of heat waves and to evaluate the ability of a syndromic surveillance system to monitor variations in the activity of emergency departments over time. The study uses data collected during the summer 2006 when a new heat wave occurred in France. Methods Data recorded from 49 emergency departments since July 2004, were transmitted daily via the Internet to the French Institute for Public Health Surveillance. Items collected on patients included diagnosis (ICD10 codes, outcome, and age. Statistical t-tests were used to compare, for several health conditions, the daily averages of patients within different age groups and periods (whether 'on alert' or 'off alert'. Results A limited number of adverse health conditions occurred more frequently during hot period: dehydration, hyperthermia, malaise, hyponatremia, renal colic, and renal failure. Over all health conditions, the total number of patients per day remained equal between the 'on alert' and 'off alert' periods (4,557.7/day vs. 4,511.2/day, but the number of elderly patients increased significantly during the 'on alert' period relative to the 'off alert' period (476.7/day vs. 446.2/day p Conclusion Our results show the interest to monitor specific indicators during hot periods and to focus surveillance efforts on the elderly. Syndromic surveillance allowed the collection of data in real time and the subsequent optimization of the response by public health agencies. This method of surveillance should therefore be considered as an essential part of efforts to prevent the health effects of heat waves.

  5. Convectively Forced Gravity Waves and their Sensitivity to Heating Profile and Atmospheric Structure

    Science.gov (United States)

    Halliday, Oliver; Parker, Douglas; Griffiths, Stephen; Vosper, Simon; Stirling, Alison

    2016-04-01

    It has been known for some time that convective heating is communicated to its environment by gravity waves. Despite this, the radiation of gravity waves in macro-scale models, which are typically forced at the grid-scale by meso-scale parameterization schemes, is not well understood. We present here theoretical work directed toward improving our fundamental understanding of convectively forced gravity wave effects at the meso-scale, in order to begin to address this problem. Starting with the hydrostatic, non-rotating, 2D, Boussinesq equations in a slab geometry, we find a radiating, analytical solution to prescribed sensible heat forcing for both the vertical velocity and potential temperature response. Both Steady and pulsed heating with adjustable horizontal structure is considered. From these solutions we construct a simple model capable of interrogating the spatial and temporal sensitivity to chosen heating functions of the remote forced response in particular. By varying the assumed buoyancy frequency, the influence of the model stratosphere on the upward radiation of gravity waves, and in turn, on the tropospheric response can be understood. Further, we find that the macro-scale response to convection is highly dependent on the radiation characteristics of gravity waves, which are in turn dependent upon the temporal and spatial structure of the source, and upper boundary condition of the domain.

  6. Seasonal analysis of cold and heat waves in Serbia during the period 1949-2012

    Science.gov (United States)

    Unkašević, Miroslava; Tošić, Ivana

    2015-04-01

    Climate change has become one of the subjects most analysed by researchers, mainly because of the numerous extreme events that have hit the globe. A series of daily minimum and maximum temperatures at 15 stations in Serbia were used to calculate temperature indices, from which the duration and severity of cold and heat waves were estimated. Seasonal analysis was based on data from 1949 to 2012. The year 2012 saw severe cooling in Serbia, the longest heat waves during the summer and the worst drought since observations began — three major climate anomalies all in 1 year. An analysis of the daily minimum temperatures at almost all meteorological stations during the winter season revealed that the longest cold waves were observed in 1956. The longest heat waves were observed during the summer of 2012 in Serbia at ten out of 15 stations, but they did not reach the severity of those in July 2007. In addition, the main characteristics of the circulation conditions which caused the longest cold and heat waves in Serbia were analysed.

  7. Can the Tibetan Plateau snow cover influence the interannual variations of Eurasian heat wave frequency?

    Science.gov (United States)

    Wu, Zhiwei; Zhang, Peng; Chen, Hua; Li, Yun

    2016-06-01

    The Eurasian continent has experienced significant year-to-year variations of summer heat waves during the past decades. Several possible factors, such as ocean temperature, soil moisture, and changes in land use and greenhouse gases, have been identified in previous studies, but the mechanisms are still unclear. In this study, it is found that the Tibetan Plateau snow cover (TPSC) is closely linked to the interannual variations of summer heat waves over Eurasia. The TPSC variability explains more than 30 % of the total variances of heat wave variability in the southern Europe and northeastern Asia (SENA) region. A set of numerical experiments reveal that the reduced TPSC may induce a distinct teleconnection pattern across the Eurasian continent, with two anomalous high pressure centers in the upper troposphere over the SENA region, which may lead to a reduction of the cloud formation near the surface. The less cloud cover tends to increase the net shortwave radiation and favor a stronger surface sensible heat flux in the dry surface condition over the SENA region, resulting in a deeper, warmer and drier atmospheric boundary layer that would further inhibit the local cloud formation. Such a positive land-atmosphere feedback may dry the surface even further, heat the near-surface atmosphere and thereby intensify the local heat waves. The above dynamical processes also operate on interdecadal time scales. Given the reduction of the TPSC could become more pronounced with increasing levels of greenhouse gases in a warming climate, we infer that the TPSC may play an increasingly important role in shaping the summer heat waves over the SENA region in next decades.

  8. COLD AND HEAT WAVES IN THE BARLAD PLATEAU BETWEEN 1961-2013

    Directory of Open Access Journals (Sweden)

    M.C. HUSTIU

    2016-03-01

    Full Text Available Among the meteorological phenomena with severe impact upon individual humans, upon society and the environment one distinguishes cold and heat waves. The geographic location of the Bârlad Plateau – east of the mountainous barrier of the Eastern Carpathians and in a region where main pressure centers travel along the year – facilitates the occurrence of cold and heat waves. Such events were analysed, for the interval 1961-2013, both as the frequency of massive warming and cooling situations, and their duration – taking as a reference intervals of at least 5 consecutive days when in any month thermal anomalies are recorded, either positive or negative.

  9. Characteristics of high frequency radio wave propagated in heated ionospheric regions

    Institute of Scientific and Technical Information of China (English)

    Fang HE; Zhengyu ZHAO

    2009-01-01

    A two-dimensional Ohm heating theoretic model in the magnetizing ionosphere and a ray-tracing model in a discrete ionosphere background are used to analyze quantitatively the characteristics (mainly the Doppler shift and the phase shift) of the over-the-horizon radar (OTHR) wave, which propagates through the ionospheric region heated by high frequency radio wave.The simulation results about the Doppler and the phase shift are obtained within two minutes after the heater is on.Preliminary conclusions are given by comparing the numerical results with experimental data.

  10. Advances in full-wave modeling of radio frequency heated, multidimensional plasmas

    International Nuclear Information System (INIS)

    Previous full-wave models for rf heating in multidimensional plasmas have relied on either cold-plasma or finite Larmor radius approximations. These models assume that the perpendicular wavelength of the rf field is much larger than the ion Larmor radius, and they are therefore limited to relatively long wavelengths and low cyclotron harmonics. Recently, alternate full-wave models have been developed that eliminate these restrictions. These 'all orders spectral algorithms' take advantage of new computational techniques for massively parallel computers to solve the integral form of the wave equation in multiple dimensions without any restriction on wavelength relative to orbit size, and with no limit on the number of cyclotron harmonics retained. These new models give high-resolution, two-dimensional solutions for mode conversion and high harmonic fast wave heating in tokamak geometry. In addition, they have been extended to give fully three-dimensional solutions of the integral wave equation for minority ion cyclotron heating in stellarator geometry. By combining multiple periodic solutions for individual helical field periods, it is possible to obtain complete wave solutions valid over the entire volume of the stellarator for arbitrary antenna geometry

  11. Refined critical balance in strong Alfvenic turbulence

    OpenAIRE

    Mallet, A.; Schekochihin, A. A.; Chandran, B. D. G.

    2014-01-01

    We present numerical evidence that in strong Alfvenic turbulence, the critical balance principle---equality of the nonlinear decorrelation and linear propagation times---is scale invariant, in the sense that the probability distribution of the ratio of these times is independent of scale. This result only holds if the local alignment of the Elsasser fields is taken into account in calculating the nonlinear time. At any given scale, the degree of alignment is found to increase with fluctuation...

  12. Metallic nanoparticles in a standing wave: Optical force and heating

    Czech Academy of Sciences Publication Activity Database

    Šiler, Martin; Chvátal, Lukáš; Zemánek, Pavel

    2013-01-01

    Roč. 126, September (2013), s. 84-90. ISSN 0022-4073 R&D Projects: GA ČR GPP205/12/P868; GA MŠk LH12018; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : Metallic nanoparticles * Optical trapping * Heating * Generalized Lorenz-Mie theory Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.288, year: 2013

  13. Simulated heat waves affected alpine grassland only in combination with drought

    Science.gov (United States)

    De Boeck, Hans J.; Bassin, Seraina; Verlinden, Maya; Zeiter, Michaela; Hiltbrunner, Erika

    2016-04-01

    The Alpine region is warming fast, leading to an increase in the frequency and intensity of climate extremes. Currently, it is unclear whether alpine ecosystems are sensitive or resistant to such extremes. In an experiment carried out in the Swiss Alps, we subjected Swiss alpine grassland communities to heat waves with varying intensity (5-10 °C warming) by transplanting monoliths to four different elevations (2440-660 m a.s.l.) for 17 days. Half of the monoliths were regularly irrigated while the other half were deprived of irrigation to additionally induce a drought at each site. We found that heat waves had no significant short-term impacts on fluorescence (Fv/Fm, a stress indicator), senescence and aboveground productivity if irrigation was provided. However, when heat waves coincided with drought, plants showed clear signs of stress, resulting in vegetation browning and reduced phytomass production. This likely resulted from direct drought effects, but also, as measurements of stomatal conductance and canopy temperatures suggest, from increased high-temperature stress as water scarcity decreased heat mitigation through transpiration. The immediate responses to heat waves (with or without droughts) recorded in these alpine grasslands were similar to those observed in the more extensively studied grasslands from temperate climates. Climate extreme impacts may differ in the longer run, however, because the short growing season in alpine environments likely constrains recovery.

  14. Simulated heat waves affected alpine grassland only in combination with drought.

    Science.gov (United States)

    De Boeck, Hans J; Bassin, Seraina; Verlinden, Maya; Zeiter, Michaela; Hiltbrunner, Erika

    2016-01-01

    The Alpine region is warming fast, and concurrently, the frequency and intensity of climate extremes are increasing. It is currently unclear whether alpine ecosystems are sensitive or resistant to such extremes. We subjected Swiss alpine grassland communities to heat waves with varying intensity by transplanting monoliths to four different elevations (2440-660 m above sea level) for 17 d. Half of these were regularly irrigated while the other half were deprived of irrigation to additionally induce a drought at each site. Heat waves had no significant impacts on fluorescence (Fv /Fm , a stress indicator), senescence and aboveground productivity if irrigation was provided. However, when heat waves coincided with drought, the plants showed clear signs of stress, resulting in vegetation browning and reduced phytomass production. This likely resulted from direct drought effects, but also, as measurements of stomatal conductance and canopy temperatures suggest, from increased high-temperature stress as water scarcity decreased heat mitigation through transpiration. The immediate responses to heat waves (with or without droughts) recorded in these alpine grasslands were similar to those observed in the more extensively studied grasslands from temperate climates. Responses following climate extremes may differ in alpine environments, however, because the short growing season likely constrains recovery. PMID:26267066

  15. Alfven eigenmodes in shear reversed plasmas

    International Nuclear Information System (INIS)

    Experiments on JT-60U and JET have shown that plasma configurations with shear reversal are prone to the excitation of unusual Alfven Eigenmodes by energetic particles. These modes emerge outside the TAE frequency gap, where one might expect them to be strongly damped. The modes often appear in bunches and they exhibit a quasi-periodic pattern of predominantly upward frequency sweeping (Alfven Cascades) as the safety factor q changes in time. This work presents a theory that explains the key features of the observed unusual modes including their connection to TAE's as well as the modifications of TAE's themselves near the shear reversal point. The developed theory has been incorporated into a reduced numerical model and verified with full geometry codes. JET experimental data on Alfven spectroscopy have been simulated to infer the mode numbers and the evolution of qmin in the discharge. This analysis confirms the values of q that characterize the internal transport barrier triggering in reversed shear plasmas. (author)

  16. Saturation of Alfven modes in tokamaks

    Science.gov (United States)

    White, Roscoe; Gorelenkov, Nikolai; Gorelenkova, Marina; Podesta, Mario; Chen, Yang

    2015-11-01

    The effect of Alfven modes on high energetic particles in tokamaks is important in general, and could be of significance for ITER. This work is a combination of analytic models and numerical simulation to find the saturation levels of unstable Alfven modes and the resulting effect on beam and alpha particle distributions. Solving the drift kinetic equation with a guiding center code in the presence of Alfven modes driven unstable by a distribution of high energy particles requires the use of a δf formalism, wherby the initial distribution f0 is assumed to be a steady state high energy particle distribution in the absense of the modes, and f =f0 + δf describes the particle distribution in the presence of the modes. The Hamiltonian is written as H =H0 +H1 with H0 giving the unperturbed motion, conserving particle energy E, toroidal canonical momentum Pζ, and magnetic moment μ. By writing the initial particle distribution in terms of these variables, a simple means of calculating mode-particle energy and momentum transfer results, giving a very accurate δf formalism.

  17. Characteristics of Short Wavelength Compressional Alfven Eigenmodes

    Energy Technology Data Exchange (ETDEWEB)

    Fredrickson, E D; Podesta, M; Bortolon, A; Crocker, N A; Gerhardt, S P; Bell, R E; Diallo, A; LeBlanc, B; Levinton, F M

    2012-12-19

    Most Alfvenic activity in the frequency range between Toroidal Alfven Eigenmodes and roughly one half of the ion cyclotron frequency on NSTX [M. Ono, et al., Nucl. Fusion 40 (2000) 557], that is, approximately 0.3 MHz up to ≈ 1.2 MHz, are modes propagating counter to the neutral beam ions. These have been modeled as Compressional and Global Alfven Eigenmodes (CAE and GAE) and are excited through a Doppler-shifted cyclotron resonance with the beam ions. There is also a class of co-propagating modes at higher frequency than the counter-propagating CAE and GAE. These modes have been identified as CAE, and are seen mostly in the company of a low frequency, n=1 kink-like mode. In this paper we present measurements of the spectrum of these high frequency CAE (hfCAE), and their mode structure. We compare those measurements to a simple model of CAE and present evidence of a curious non-linear coupling of the hfCAE and the low frequency kink-like mode.

  18. Modelling Ion Cyclotron Resonance Heating and Fast Wave Current Drive in Tokamaks

    OpenAIRE

    Hannan, Abdul

    2013-01-01

    Fast magnetosonic waves in the ion cyclotron range of frequencies have the potential to heat plasma and drive current in a thermonuclear fusion reactor. A code, SELFO-light, has been developed to study the physics of ion cyclotron resonantheating and current drive in thermonuclear fusion reactors. It uses a global full wave solver LION and a new 1D Fokker-Planck solver for the self-consistent calculations of the wave field and the distribution function of ions.In present day tokamak experimen...

  19. Do asteroids evaporate near pulsars? Induction heating by pulsar waves revisited

    CERN Document Server

    Kotera, Kumiko; Voisin, Guillaume; Heyvaerts, Jean

    2016-01-01

    We investigate the evaporation of close-by pulsar companions, such as planets, asteroids, and white dwarfs, by induction heating. Assuming that the outflow energy is dominated by a Poynting flux (or pulsar wave) at the location of the companions, we calculate their evaporation timescales, by applying the Mie theory. Depending on the size of the companion compared to the incident electromagnetic wavelength, the heating regime varies and can lead to a total evaporation of the companion. In particular, we find that inductive heating is mostly inefficient for small pulsar companions, although it is generally considered the dominant process. Small objects like asteroids can survive induction heating for $10^4\\,$years at distances as small as $1\\,R_\\odot$ from the neutron star. For degenerate companions, induction heating cannot lead to evaporation and another source of heating (likely by kinetic energy of the pulsar wind) has to be considered. It was recently proposed that bodies orbiting pulsars are the cause of ...

  20. A new approach to the theory of heat conduction with finite wave speeds

    Directory of Open Access Journals (Sweden)

    Vito Antonio Cimmelli

    1991-05-01

    Full Text Available Relations between the physical models describing the heat conduction in solids and a phenomenological model leading to quasi-linear hyperbolic equations and systems of conservation laws are presented. A new semi-empirical temperature scale is introduced in terms of which a modified Fourier law is formulated. The hyperbolicity of the heat conduction equation is discussed together with some wave propagation problems.

  1. Anomalous attenuation of extraordinary waves in ionosphere heating experiments experimental results of 2000-2001

    CERN Document Server

    Zabotin, N A; Kovalenko, E S; Frolov, V L; Komrakov, G P; Mityakov, N A; Sergeev, E N

    2001-01-01

    Multiple scattering from artificial random irregularities HF-induced in the ionosphere F region causes significant attenuation of both ordinary and extraordinary radio waves together with the conventional anomalous absorption of ordinary waves due to their conversion into the plasma waves. To study in detail features of this effect, purposeful measurements of the attenuation of weak probing waves of the extraordinary polarization have been performed at the Sura heating facility. Characteristic scale lengths of the involved irregularities are ~0.1-1 km across the geomagnetic field lines. To determine the spectral characteristics of these irregularities from the extraordinary probing wave attenuation measurements, a simple procedure of the inverse problem solving has been implemented and some conclusions about the artificial irregularity features have been drawn. Theory and details of experiments have been stated earlier. This paper reports results of two experimental campaigns carried out in August 2000 and Ju...

  2. Analysis of mesoscale heating by piston supported waves in granular metalized explosive

    International Nuclear Information System (INIS)

    Deformation-induced heating of explosive composites is influenced by the material microstructure (i.e. porosity and particle sizes, shapes and packing), and component-specific thermomechanical properties and mass fractions. In this study, an explicit, 2D, Lagrangian finite and discrete element technique is used to examine thermomechanical fields in mixtures of explosive (HMX, C4H8N8O8) and metal particles (Al) induced by piston-supported deformation waves (piston speed 50 ⩽ Up ⩽ 500 m s−1). The mesoscale description uses a plane strain, thermoelastic–viscoplastic and friction constitutive theory to describe the motion and deformation of individual particles, and an energy consistent, penalty based method to describe inter-particle contact. The deformation response of material having an initial solid volume fraction of φs0 = 0.835 (porosity 1 − φs0 = 0.165) is characterized for different metal mass fractions and wave strengths. Transition from a strength-dominated to a pressure-dominated wave structure is predicted to occur with increasing wave strength due to the elimination of porosity. Average thermomechanical fields that define the effective wave structure differ both qualitatively and quantitatively for the two types of structures. Explosive component mass locally heated to elevated temperature behind waves is shown to be affected by the wave structure and the value of friction coefficient. (paper)

  3. Individual and Public-Program Adaptation: Coping with Heat Waves in Five Cities in Canada

    Directory of Open Access Journals (Sweden)

    Mustapha Alhassan

    2011-12-01

    Full Text Available Heat Alert and Response Systems (HARS are currently undergoing testing and implementation in Canada. These programs seek to reduce the adverse health effects of heat waves on human health by issuing weather forecasts and warnings, informing individuals about possible protections from excessive heat, and providing such protections to vulnerable subpopulations and individuals at risk. For these programs to be designed effectively, it is important to know how individuals perceive the heat, what their experience with heat-related illness is, how they protect themselves from excessive heat, and how they acquire information about such protections. In September 2010, we conducted a survey of households in 5 cities in Canada to study these issues. At the time of the survey, these cities had not implemented heat outreach and response systems. The study results indicate that individuals’ recollections of recent heat wave events were generally accurate. About 21% of the sample reported feeling unwell during the most recent heat spell, but these illnesses were generally minor. Only in 25 cases out of 243, these illnesses were confirmed or diagnosed by a health care professional. The rate at which our respondents reported heat-related illnesses was higher among those with cardiovascular and respiratory illnesses, was higher among younger respondents and bore no relationship with the availability of air conditioning at home. Most of the respondents indicated that they would not dismiss themselves as “not at risk” and that they would cope with excessive heat by staying in air conditioned environments and keeping well hydrated. Despite the absence of heat outreach and education programs in their city, our respondents at least a rough idea of how to take care of themselves. The presence of air conditioning and knowledge of cooling centers is location-specific, which provides opportunities for targeting HARS interventions.

  4. Recent changes in air temperature, heat waves occurrences, and atmospheric circulation in Northern Africa

    Science.gov (United States)

    Fontaine, Bernard; Janicot, Serge; Monerie, Paul-Arthur

    2013-08-01

    study documents the time evolution of air temperature and heat waves occurrences over Northern Africa for the period 1979-2011. A significant warming (1°-3°C), appearing by the mid-1960s over Sahara and Sahel, is associated with higher/lesser frequency of warm/cold temperatures, as with longer duration and higher occurrences of heat waves. Heat waves episodes of at least 4 day duration have been examined after removing the long-term evolution. These episodes are associated with specific anomalies: (i) in spring, positive low-level temperature anomalies over the Sahel and Sahara; low and midlevel cyclonic rotation over Morocco associated with a Rossby wave pattern, lessening the Harmattan; more/less atmospheric moisture westward/eastward to 0°; upward/downward anomalies above the western/eastern regions associated with the Rossby wave pattern; (ii) in summer, a similar but weaker positive low-level temperature anomaly (up to 3°C); less moisture westward to 10°W, a cyclonic anomaly in central Sahel favoring the monsoon eastward to 0° and a midlevel anticyclonic anomaly over the Western Sahara, increasing southward the flux divergence associated with the African Easterly Jet. In March-May, two to three heat waves propagate eastward. They are preceded by an abnormal warm cell over Libya and southwesterlies over the West Sahara. A large trough stands over North Atlantic while midtropospheric subsidence and anticyclonic rotation reinforce over the continent, then migrates toward the Arabian peninsula in breaking up. These signals are spatially coherent and might suggest the role of short Rossby waves with an eastward group velocity and a baroclinic mode, possibly associated with jet stream deformation.

  5. Star of Lima - Overview and optical diagnostics of a barium Alfven critical velocity experiment

    Science.gov (United States)

    Wescott, E. M.; Stenbaek-Nielsen, H. C.; Hallinan, T.; Foeppl, H.; Valenzuela, A.

    1986-01-01

    The Alfven critical velocity mechanism for ionization of a neutral gas streaming across the magnetic field has been demonstrated in laboratory experiments. In March 1983, two rocket-borne experiments with Ba and Sr tested the effect in the wall-less laboratory of space from Punto Lobos, Peru, near 430 km altitude. 'Star of Lima' used a conical Ba shaped charge aimed at an instrument payload about 2 km away. Because of rocket overperformance the detonation occurred in partial sunlight, so that less than 21.6 percent of the ionizing UV was present. Particle and field measurements indicate the production of hot electrons and waves in the energy and frequency range that are respectively predicted to produce a cascade of ionization by the Alfven mechanism. However, the ionization fluxes and wave energy density did not reach cascade levels, and optical observations indicate that only 2.5 to 5 x 10 to the 20th Ba ions were produced. A substantial portion and perhaps all of the ionization could have been produced by solar UV. The failure of the Alfven process in this experiment is not well understood.

  6. Alfvén wave solar model (AWSoM): Coronal heating

    International Nuclear Information System (INIS)

    We present a new version of the Alfvén wave solar model, a global model from the upper chromosphere to the corona and the heliosphere. The coronal heating and solar wind acceleration are addressed with low-frequency Alfvén wave turbulence. The injection of Alfvén wave energy at the inner boundary is such that the Poynting flux is proportional to the magnetic field strength. The three-dimensional magnetic field topology is simulated using data from photospheric magnetic field measurements. This model does not impose open-closed magnetic field boundaries; those develop self-consistently. The physics include the following. (1) The model employs three different temperatures, namely the isotropic electron temperature and the parallel and perpendicular ion temperatures. The firehose, mirror, and ion-cyclotron instabilities due to the developing ion temperature anisotropy are accounted for. (2) The Alfvén waves are partially reflected by the Alfvén speed gradient and the vorticity along the field lines. The resulting counter-propagating waves are responsible for the nonlinear turbulent cascade. The balanced turbulence due to uncorrelated waves near the apex of the closed field lines and the resulting elevated temperatures are addressed. (3) To apportion the wave dissipation to the three temperatures, we employ the results of the theories of linear wave damping and nonlinear stochastic heating. (4) We have incorporated the collisional and collisionless electron heat conduction. We compare the simulated multi-wavelength extreme ultraviolet images of CR2107 with the observations from STEREO/EUVI and the Solar Dynamics Observatory/AIA instruments. We demonstrate that the reflection due to strong magnetic fields in the proximity of active regions sufficiently intensifies the dissipation and observable emission.

  7. Electromagnetic internal gravity waves in the Earth's ionospheric E-layer

    International Nuclear Information System (INIS)

    In the Earth's ionospheric E-layer existence of the new waves connecting with the electromagnetic nature of internal gravity waves is shown. They represent the mixture of the ordinary internal gravity waves and the new type of dispersive Alfven waves. -- Highlights: ► Existence of electromagnetic internal gravity waves in the ionospheric E-layer is shown. ► Electromagnetic nature of internal gravity waves is described. ► Appearance of the new dispersive Alfven waves is shown.

  8. Projection of Heat Waves over China under Different Global Warming Targets

    Science.gov (United States)

    Guo, Xiaojun; Luo, Yong; Huang, Jianbin; Zhao, Zongci

    2015-04-01

    Global warming targets, which are determined in terms of global mean temperature increases relative to pre-industrial temperature levels, have been one of the heated issues recently. And the climate change (especially climate extremes) and its impacts under different targets have been paid extensive concerns. In this study, evaluation and projection of heat waves in China were carried out by five CMIP5 global climate models (GCMs) with a 0.5°×0.5° horizontal resolution which were derived from EU WATCH project. A new daily observed gridded dataset CN05.1 (0.5°×0.5°) was also used to evaluate the GCMs. And four indices (heat waves frequency, longest heat waves duration, heat waves days and high temperature days) were adopted to analyze the heat waves. Compared with the observations, the five GCMs and its Multi-Model Ensemble (MME) have a remarkable capacity of reproducing the spatial and temporal characteristic of heat waves. The time correlation coefficients between MME and the observation results can all reach 0.05 significant levels. Based on the projection data of five GCMs, both the median year of crossing 1.5°C, 2°C, 2.5°, 3°C, 3.5°C, 4°C, 4.5°C and 5°C global warming targets and the corresponding climate change over China were analyzed under RCP 4.5 and RCP 8.5 scenarios, respectively. The results show that when the global mean surface air temperature rise to different targets with respect to the pre-industrial times (1861-1880), the frequency and intensity of heat waves will increase dramatically. To take the high emission scenario RCP8.5 as an example, under the RCP8.5 scenario, the warming rate over China is stronger than that over the globe, the temperature rise(median year) over China projected by MME are 1.77°C(2025), 2.63°C(2039), 3.39°C(2050), 3.97°C(2060), 4.82°C(2070), 5.47°C(2079) and 6.2°C(2089) under 1.5°C, 2°C, 2.5°C, 3°C, 3.5°C, 4°C and 4.5°C global warming targets, respectively. With the increase of the global

  9. Solitary heat waves in nonlinear lattices with squared on-site potential

    Indian Academy of Sciences (India)

    Rovinita Perseus; M M Latha

    2013-06-01

    A model Hamiltonian is proposed for heat conduction in a nonlinear lattice with squared on-site potential using the second quantized operators and averaging the same using a suitable wave function, equations are derived in discrete form for the field amplitude and the properties of heat transfer are examined theoretically. Numerical analysis shows that the propagation of heat is in the form of solitons. Furthermore, a systemized version of tanh method is carried out to extract solutions for the resulting nonlinear equations in the continuum case and the effect of inhomogeneity is studied for different temperatures.

  10. Plasma heating and acceleration by strong magnetosonic waves propagating obliquely to a magnetostatic field

    International Nuclear Information System (INIS)

    The behavior of strong magnetosonic waves with ω>ω/sub c/i (ω/sub c/i = q/sub i/B/m/sub i/c) is investigated in oblique propagation with particle simulation. Strong ion and electron heatings versus the angle [theta = (k,B0)] are found for theta0. Ion heating peaks at a particular angle but disappears below a critical angle theta/sub t//sub i/; electron heating sets in below a second critical angle theta/sub t//sub e/. The phenomena exhibit unexpected structure with theta

  11. Electron anomalous heating in the field of oblique Langmuir waves in induced ls-scattering

    International Nuclear Information System (INIS)

    The anomalous electron heating by high frequency fields near the hybrid resonance in a plasma with ion-sound instability is considered. In the analysis of the measurement results the increase of high frequency wave energy density due to scattering the pumling wave and also the effect of variation of the plasma potential on the energy losses of the electrons along the magnetic field are taken into account. It is shown that electron heating may be explained by introducing effective collision frequency by an order of magnitude. The thermal and electric conductivities of the plasma along the magnetic field are found to decrease. A correlation between the electron heating and high frequency field excitation of ion-sound waves is observed. It is shown that the excitation of ion-sound waves may be explained by induced ls-scattering of waves in a plasma with a current. By comparing the results of the measurements and the results of the theory of induced ls-scattering it is concluded that within the framework of weak turbulence theory only the effect of energy gain by electrons in a high frequency field can be explined whereas the observed effect of loss of momentum component along t.n.e magnetic field cannot be explained

  12. The 2010 Pakistan Flood and Russian Heat Wave: Teleconnection of Hydrometeorological Extremes

    Science.gov (United States)

    Lau, William K. M.; Kim, Kyu-Myong

    2012-01-01

    In this paper, preliminary results are presented showing that the two record-setting extreme events during 2010 summer (i.e., the Russian heat wave-wildfires and Pakistan flood) were physically connected. It is found that the Russian heat wave was associated with the development of an extraordinarily strong and prolonged extratropical atmospheric blocking event in association with the excitation of a large-scale atmospheric Rossby wave train spanning western Russia, Kazakhstan, and the northwestern China-Tibetan Plateau region. The southward penetration of upper-level vorticity perturbations in the leading trough of the Rossby wave was instrumental in triggering anomalously heavy rain events over northern Pakistan and vicinity in mid- to late July. Also shown are evidences that the Russian heat wave was amplified by a positive feedback through changes in surface energy fluxes between the atmospheric blocking pattern and an underlying extensive land region with below-normal soil moisture. The Pakistan heavy rain events were amplified and sustained by strong anomalous southeasterly flow along the Himalayan foothills and abundant moisture transport from the Bay of Bengal in connection with the northward propagation of the monsoonal intraseasonal oscillation.

  13. On climate model simulations of the large-scale meteorology associated with California heat waves

    Science.gov (United States)

    Grotjahn, Richard; Lee, Yun-Young

    2016-01-01

    Previous work considered how well the large-scale meteorological patterns (LSMPs) associated with California Central Valley heat waves are captured by a climate model. Recent work found two distinct types of LSMPs and key parcel trajectories occurring prior to heat wave onset. This study searches for those two types of heat waves in two additional reanalyses and in historical simulations by 14 climate models. The reanalyses develop both types with similar properties; their differences are used as a conservative estimate of acceptable differences between data sets. All the models develop heat waves of both types, but the models vary quite a bit in the separation between the two types, the magnitudes of the two types, and the frequency of occurrence of the two types. The best models match a third to a half of the properties found in reanalyses. Models tend to have lower valued projections onto the two types than reanalyses, consistent with a systematic tendency to center the hottest 850 hPa temperatures onshore instead of just offshore. Models of higher horizontal resolution tend to simulate better the two types. There is some evidence that models with a low top (with relatively poorly resolved stratosphere) also simulate the clusters better.

  14. GRACE-derived terrestrial water storage depletion associated with the 2003 European heat wave

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Seneviratne, S.I.; Hinderer, J.; Viterbo, P.

    2005-01-01

    water storage depletion observed from GRACE can be related to the record-breaking heat wave that occurred in central Europe in 2003. We validate the measurements from GRACE using two independent hydrological estimates and direct gravity observations from superconducting gravimeters in Europe. All...

  15. Resilience to seasonal heat wave episodes in a Mediterranean pine forest.

    Science.gov (United States)

    Tatarinov, Fedor; Rotenberg, Eyal; Maseyk, Kadmiel; Ogée, Jérôme; Klein, Tamir; Yakir, Dan

    2016-04-01

    Short-term, intense heat waves (hamsins) are common in the eastern Mediterranean region and provide an opportunity to study the resilience of forests to such events that are predicted to increase in frequency and intensity. The response of a 50-yr-old Aleppo pine (Pinus halepensis) forest to hamsin events lasting 1-7 d was studied using 10 yr of eddy covariance and sap flow measurements. The highest frequency of heat waves was c. four per month, coinciding with the peak productivity period (March-April). During these events, net ecosystem carbon exchange (NEE) and canopy conductance (gc ) decreased by c. 60%, but evapotranspiration (ET) showed little change. Fast recovery was also observed with fluxes reaching pre-stress values within a day following the event. NEE and gc showed a strong response to vapor pressure deficit that weakened as soil moisture decreased, while sap flow was primarily responding to changes in soil moisture. On an annual scale, heat waves reduced NEE and gross primary productivity by c. 15% and 4%, respectively. Forest resilience to short-term extreme events such as heat waves is probably a key to its survival and must be accounted for to better predict the increasing impact on productivity and survival of such events in future climates. PMID:27000955

  16. Numerical solutions to integrodifferential equations which interpolate heat and wave equations

    OpenAIRE

    Rozmej, Piotr; Karczewska, Anna

    2005-01-01

    In the paper we study some numerical solutions to Volterra equations which interpolate heat and wave equations. We present a scheme for construction of approximate numerical solutions for one and two spatial dimensions. Some solutions to the stochastic version of such equations (for one spatial dimension) are presented as well.

  17. Heat waves over Central Europe in regional climate models: evaluation and future projections

    Czech Academy of Sciences Publication Activity Database

    Lhotka, Ondřej; Kyselý, Jan

    Berlín: European Meteorological Society, 2015. EMS2015-135. [EMS Annual Meeting /15./ and European Conference on Applied Climatology /12./. 07.09.2015–11.09.2015, Sofia] Institutional support: RVO:68378289 Keywords : regional climate model ( RCM ) * heat waves * Central Europe Subject RIV: DG - Athmosphere Sciences, Meteorology http://meetingorganizer.copernicus.org/EMS2015/EMS2015-135.pdf

  18. Alfvén wave heating of heavy ions in the expanding solar wind: Hybrid simulations

    Czech Academy of Sciences Publication Activity Database

    Hellinger, Petr; Velli, M.; Trávníček, Pavel; Gary, S. P.; Goldstein, B. E.; Liewer, P. C.

    2005-01-01

    Roč. 110, - (2005), A12109/1-A12109/11. ISSN 0148-0227 R&D Projects: GA AV ČR IAA3042403 Institutional research plan: CEZ:AV0Z30420517 Keywords : Alfvén waves * solar wind heating * microinstabilities Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 2.784, year: 2005

  19. The Bermuda Triangle mysteries: an explanation based on the diffraction of heat waves

    Energy Technology Data Exchange (ETDEWEB)

    Njau, E.C. [Dar es Salaam Univ. (Tanzania, United Republic of). Dept. of Physics

    1995-12-31

    Studies based on actual meteorological records [E.C. Njau, Nuovo Cimento 15C, 17-23 (1992)] as well as analytical methods [E.C. Njau, Proc. Ind. Natn. Sci. Acad., 61A (4) (1995); Renewable Energy 4, 261-263 (1994)] have established the continuous existence of a series of large-scale, Eastward-moving heat waves along the Earth`s surface, whose individual crests and troughs are stretched approximately along the geographical North-South direction. In moving across the American continent, these waves encounter a line of physical barriers formed by the lofty Rocky and Andes ranges of mountains, which is continuous except for a significant gap or opening between Colombia and Mexico. This line of physical barriers consistently maintains a maximum height of 3000-4000 m between latitudes 40{sup o}S and 55{sup o}N except for a significant opening or slit located between Mexico and Colombia where the maximum height hardly exceeds 600 m. The Eastward-moving heat waves are thus incident obliquely on an approximately single-slit barrier when crossing the American continent and those parts of the waves which filter through this single slit essentially form some kind of single-slit diffraction (heat) patterns in, around and past the Bermuda Triangle. These diffraction heat patterns give rise to corresponding weather and ocean patterns which, to a large extent, account for the mysteries already noted in the Bermuda region. (Author)

  20. Mode-converted electron Bernstein waves for heating and current drive in NSTX

    International Nuclear Information System (INIS)

    The power coupled to electron Bernstein waves in a triplet mode conversion resonator from a fast X-mode at the plasma edge in NSTX is shown to be > 80% for fce ce. The EBW damping in the plasma is strong and localized and, thus, should be useful for heating, current drive, or profile control. (author)

  1. Heat wave over India during summer 2015: an assessment of real time extended range forecast

    Science.gov (United States)

    Pattanaik, D. R.; Mohapatra, M.; Srivastava, A. K.; Kumar, Arun

    2016-06-01

    Hot winds are the marked feature of summer season in India during late spring preceding the climatological onset of the monsoon season in June. Some years the conditions becomes very vulnerable with the maximum temperature (T max) exceeding 45 °C for many days over parts of north-western, eastern coastal states of India and Indo-Gangetic plain. During summer of 2015 (late May to early June) eastern coastal states, central and northwestern parts of India experienced severe heat wave conditions leading to loss of thousands of human life in extreme high temperature conditions. It is not only the loss of human life but also the animals and birds were very vulnerable to this extreme heat wave conditions. In this study, an attempt is made to assess the performance of real time extended range forecast (forecast up to 3 weeks) of this scorching T max based on the NCEP's Climate Forecast System (CFS) latest version coupled model (CFSv2). The heat wave condition was very severe during the week from 22 to 28 May with subsequent week from 29 May to 4 June also witnessed high T max over many parts of central India including eastern coastal states of India. The 8 ensemble members of operational CFSv2 model are used once in a week to prepare the weekly bias corrected deterministic (ensemble mean) T max forecast for 3 weeks valid from Friday to Thursday coinciding with the heat wave periods of 2015. Using the 8 ensemble members separately and the CFSv2 corresponding hindcast climatology the probability of above and below normal T max is also prepared for the same 3 weeks. The real time deterministic and probabilistic forecasts did indicate impending heat wave over many parts of India during late May and early June of 2015 associated with strong northwesterly wind over main land mass of India, delaying the sea breeze, leading to heat waves over eastern coastal regions of India. Thus, the capability of coupled model in providing early warning of such killer heat wave can be very

  2. Experimental studies of Alfven mode stability in the JET tokamak

    International Nuclear Information System (INIS)

    Controlling the interaction between fusion generated α's and modes in the Alfven frequency range is a crucial issue for the operation of experimental reactors in the burning plasma regime, such as ITER, as these modes can be driven unstable by the slowing-down α's up to amplitudes at which they could cause rapid radial transport of the α's themselves. The need to avoid strongly unstable regimes for some classes of Alfven Eigenmodes (AEs) could therefore provide additional operational limits for the reactor regime. On the other hand, if adequate actuators are identified, AEs could be used to affect the thermonuclear plasma burn in a controlled way. Two classes of investigations are conducted on JET to directly observe the AE stability limits in the presence of fast particles that can resonate with the modes and to measure the damping rate of the modes as a function of the plasma parameters, in order to quantify the mechanisms that provide background damping for the modes in different conditions. Sections 2 and 3 describe experiments from the first class, addressing the AE stability threshold for different fast ion radial distributions, generated at different locations by additional heating or at different plasma densities, or modified by the presence of error field mode. Examples from the second class are described in Section 4. During the last two years a particular effort was undertaken to complete the database of damping rate measurements of low toroidal mode numbers using the saddle coil active AE excitation system, which is being dismantled during the 2004 JET shutdown. A new antenna system is under development to continue along the same lines, but extending the accessible range of toroidal mode numbers to higher values, up to n >>10-15, of more direct relevance to ITER. This system is described in Section 5

  3. Features of amplitude and Doppler frequency variation of ELF/VLF waves generated by "beat-wave" HF heating at high latitudes

    Science.gov (United States)

    Tereshchenko, E. D.; Shumilov, O. I.; Kasatkina, E. A.; Gomonov, A. D.

    2014-07-01

    Observations of extremely low frequency (ELF, 3-3000 Hz) radio waves generated by a "beat-wave" (BW) high frequency (~ 4.04-4.9 MHz) ionospheric heating are presented. ELF waves were registered with the ELF receiver located at Lovozero (68°N, 35°E), 660 km east from the European Incoherent Scatter Tromso heating facility (69.6°N, 19.2°E). Frequency shifts between the generated beat-wave and received ELF waves were detected in all sessions. It is shown that the amplitudes of ELF waves depend on the auroral electrojet current strength. Our results showing a strong dependence of ELF signal intensities on the substorm development seem to support the conclusion that electrojet currents may affect the BW generation of ELF/VLF waves.

  4. Study of clay behaviour around a heat source by frequency spectrum analysis of seismic waves

    International Nuclear Information System (INIS)

    Wave propagated into soft rock is not completely described by purely linear elastic theory. Through spectrum analysis of wave, one can see that several frequencies are selected by the ground. ME2i uses this method to check grouting, piles a.s.o. The Mol experiment (on Radioactive Waste Disposal) aims to prove that little changes into heated clay can be detected by 'frequential seismic'. A cross-hole investigation system has been installed and tests have been performed for two years with a shear-hammer named MARGOT built to work inside horizontal boreholes: - Before heating the tests show the same results every time: . main frequency at 330 hertz; . maximal frequency at 520 hertz; - During heating: . the rays at 330 and 520 hertz disappear; . The frequencies in the range 100 - 300 hertz are prevailing; - After heating spectra have again their original shape. These results show that the effect is clear around an heated zone. The next steps should be: - Interpretation with computer's codes treating of wave propagation into a viscoelastic body; - Experimentations: . at the opening of a new gallery; . on big samples; . on granites and salt. 9 refs., 4 appendices

  5. Intercomparison of the Russian Summer Heat Waves of 2010 and 1972

    Science.gov (United States)

    Zveryaev, I.; Zyulyaeva, Yu.; Gulev, S.; Koltermann, P.

    2012-04-01

    Gridded monthly and daily data from the NCEP/NCAR reanalysis and some other data sets are used to investigate and inter-compare climatological background and intraseasonal evolution of the two strongest Russian summer heat waves of 2010 and 1972 that impacted significantly the economy and living conditions in European Russia. Despite the similar impact of the two heat waves, the climatological background for their development was quite different in 2010 and 1972. In particular, sea surface temperature (SST) anomaly patterns in the North Atlantic (which could potentially affect the development of the heat waves) were different, reflecting basin-scale positive SST anomaly in 2010 and so-called tripole pattern in 1972. Structure of the sea level pressure (SLP) anomalies indicating dominant regimes of the atmospheric dynamics, was also different 2010 and 1972. In particular, the summer of 1972 was characterized by the positive phase of the North Atlantic Oscillation (NAO), whereas in 2010 the NAO was in its slightly negative phase. Intraseasonal evolution of the two Russian summer heat waves was also quite different and characterized by the longer-term air temperature fluctuations in 2010 compared to those in 1972. Furthermore, in contrast to 1972 when no relation to the NAO (and regional atmospheric dynamics in general) on intraseasonal time scale has been revealed, significant positive correlation (0.56) with the NAO index have been found in 2010. Analysis of links between leading EOF modes of regional SLP and air temperature over European Russia has revealed that neither EOF-1, nor EOF-2 has been associated with intraseasonal air temperature variability in 1972, thus indicating relatively minor role of regional atmospheric dynamics in driving this variability. On the contrary, in 2010 regional air temperature variability was mainly driven by the NAO-associated EOF-1 of regional SLP. Hence, present results suggest that in 2010 and 1972 the NAO affected the Russian

  6. Protoplanetary Disk Heating and Evolution Driven by the Spiral Density Waves

    CERN Document Server

    Rafikov, Roman R

    2016-01-01

    High-resolution imaging of some protoplanetary disks in scattered light reveals presence of the global spiral arms of significant amplitude, likely excited by massive planets or stellar companions. Assuming that these arms are density waves, evolving into spiral shocks, we assess their effect on the thermodynamics, accretion, and global evolution of the disk. We derive analytical expressions for the direct (irreversible) heating, angular momentum transport, and mass accretion rate induced by the disk shocks of arbitrary strength. We find these processes to be very sensitive to the shock amplitude. Focusing on the waves of moderate strength (density jump at the shock $\\Delta\\Sigma/\\Sigma\\sim 1$) we show the associated disk heating to be negligible (contributing at $\\sim 1\\%$ level to the energy budget) in passive, irradiated protoplanetary disks on $\\sim 100$ AU scales, but becoming important within several AU from the star. At the same time, shock heating can be a significant (or even dominant) energy source ...

  7. Pressure and wall heat transfer behind a hydrogen/azide detonation wave in narrow tubes

    International Nuclear Information System (INIS)

    The reported study is concerned with the pressure evolution behind the detonation wave in tubes with an interior diameter in the range from 1 to 10 mm. Hydrogen azide in tubes with length-to-diameter ratios greater than 375 was detonated. The initial pressures were in the range from 1 to 20 Torr. The pressure behind the leading shock was measured with piezoelectrical transducers made of lead titanate and lead zirconate. It was found that the detonation velocity depends on wall heat losses. The wall heat flux observed behind the wave front was not in agreement with that calculated for constant flow parameters. In the diameter and pressure range considered, the wall heat flux varies strongly with tube diameter. This observation can be related to flow deviations regarding the Chapman-Jouguet parameters

  8. Radiofrequency heating design study for TNS

    Energy Technology Data Exchange (ETDEWEB)

    Pridgeon, T.H.

    1978-03-01

    This report is divided into two sections, corresponding to two different phases of a research and design study. In the first section, a brief comparison study is presented of the various RF heating methods under consideration for tokamak application. These methods include: electron cyclotron resonance heating (ECRH), lower hybrid heating, ion cyclotron range of frequencies heating (ICRF), ion cyclotron resonance heating (ICRH), magnetoacoustic wave heating, and shear Alfven wave heating. Each method is examined according to the type(s) of plasma waves involved, wave propagation and accessibility, dominant absorption processes, possible coupling structures, expected efficiencies, and expected engineering difficulties. A specific tokamak application was chosen to provide self-consistent boundary conditions for the study. The second part of this report deals with the application of ICRF to TNS. Although coupling theory for ICRF is very uncertain at this time for devices as large as TNS, waveguides operating at a frequency equal to twice the deuteron cyclotron frequency are considered as possible coupling structures. A possible design is presented that has been arrived at through consideration of several factors.

  9. Radiofrequency heating design study for TNS

    International Nuclear Information System (INIS)

    This report is divided into two sections, corresponding to two different phases of a research and design study. In the first section, a brief comparison study is presented of the various RF heating methods under consideration for tokamak application. These methods include: electron cyclotron resonance heating (ECRH), lower hybrid heating, ion cyclotron range of frequencies heating (ICRF), ion cyclotron resonance heating (ICRH), magnetoacoustic wave heating, and shear Alfven wave heating. Each method is examined according to the type(s) of plasma waves involved, wave propagation and accessibility, dominant absorption processes, possible coupling structures, expected efficiencies, and expected engineering difficulties. A specific tokamak application was chosen to provide self-consistent boundary conditions for the study. The second part of this report deals with the application of ICRF to TNS. Although coupling theory for ICRF is very uncertain at this time for devices as large as TNS, waveguides operating at a frequency equal to twice the deuteron cyclotron frequency are considered as possible coupling structures. A possible design is presented that has been arrived at through consideration of several factors

  10. Detection of Ionospheric Alfven Resonator Signatures Onboard C/NOFS: Implications for IRI Modeling

    Science.gov (United States)

    Simoes, F.; Klenzing, J.; Ivanov, S.; Pfaff, R.; Rowland, D.; Bilitza, D.

    2011-01-01

    The 2008-2009 long-lasting solar minimum activity has been the one of its kind since the dawn of space age, offering exceptional conditions for investigating space weather in the near-Earth environment. First ever detection of Ionospheric Alfven Resonator (IAR) signatures in orbit offers new means for investigating ionospheric electrodynamics, namely MHD (MagnetoHydroDynamics) wave propagation, aeronomy processes, ionospheric dynamics, and Sun-Earth connection mechanisms at a local scale. Local and global plasma density heterogeneities in the ionosphere and magnetosphere allow for formation of waveguides and resonators where magnetosonic and shear Alfven waves propagate. The ionospheric magnetosonic waveguide results from complete magnetosonic wave reflection about the ionospheric F-region peak, where the Alfven index of refraction presents a maximum. MHD waves can also be partially trapped in the vertical direction between the lower boundary of the ionosphere and the magnetosphere, a resonance mechanism known as IAR. In this work we present C/NOFS (Communications/Navigation Outage Forecasting System) Extremely Low Frequency (ELF) electric field measurements related to IAR signatures, discuss the resonance and wave propagation mechanisms in the ionosphere, and address the electromagnetic inverse problem from which electron/ion distributions can be derived. These peculiar IAR electric field measurements provide new, complementary methodologies for inferring ionospheric electron and ion density profiles, and also contribute for the investigation of ionosphere dynamics and space weather monitoring. Specifically, IAR spectral signatures measured by C/NOFS contribute for improving the International Reference Ionosphere (IRI) model, namely electron density and ion composition.

  11. Helium blast-wave measurements of laser-heated microshell targets

    International Nuclear Information System (INIS)

    Measurements of blast waves produced by laser heating of spherical glass-shell targets in an atmosphere of 20 Torr helium are described. These measurements made use of a streak camera, monitoring the self-luminosity of the strong shock, a blast probe detecting the ionization behind the shock front, and a piezoelectric pressure probe recording the pressure pulse of the shock. The time history of the blast wave is used to determine the kinetic energy of target dissembly via a simple model which is applicable in both the strong-shock and acoustic regions. These measurements show that the inferred blast-wave energy increases for larger radius--time-shock coordinates. This anomalous effect is ascribed to ''fast'' ion preheating of the ambient helium gas in front of the shock wave

  12. Competition between shock and turbulent heating in coronal loop system

    CERN Document Server

    Matsumoto, Takuma

    2016-01-01

    2.5-dimensional magnetohydrodynamic (MHD) simulations are performed with high spatial resolution in order to distinguish between competing models of the coronal heating problem. A single coronal loop powered by Alfv\\'{e}n waves excited in the photosphere is the target of the present study. The coronal structure is reproduced in our simulations as a natural consequence of the transportation and dissipation of Alfv\\'{e}n waves. Further, the coronal structure is maintained as the spatial resolution is changed from 25 to 3 km, although the temperature at the loop top increases with the spatial resolution. The heating mechanisms change gradually across the magnetic canopy at a height of 4 Mm. Below the magnetic canopy, both the shock and the MHD turbulence are dominant heating processes. Above the magnetic canopy, the shock heating rate reduces to less than 10 % of the total heating rate while the MHD turbulence provides significant energy to balance the radiative cooling and thermal conduction loss or gain. The i...

  13. Formation and disruption of Alfvenic filaments in Hall magnetohydrodynamics

    International Nuclear Information System (INIS)

    In magnetohydrodynamics with Hall effect (Hall-MHD), weakly nonlinear quasimonochromatic dispersive Alfven waves propagating along an ambient magnetic field can develop to transverse instabilities leading to the formation of intense magnetic filaments. This phenomenon, described as a transverse collapse within the asymptotic approach provided by the nonlinear Schroedinger equation for the pump envelope, was also reproduced by spectral direct numerical simulations of the Hall-MHD system. We address here the dynamics at longer times, using a finite difference scheme with adaptive mesh refinement to reproduce a strong filamentation regime, supplemented by a shock capturing scheme in the final phase of the simulations. We observe a strong distortion of the early time cylindrical filaments, associated with flattening and twisting of the structures and the transition from nonlinear waves to a hydrodynamic regime, characterized by intense current sheets and a strong acceleration of the plasma. A configuration where the intensity of the magnetic filaments saturates while the velocity field is still growing is also identified in the spectral simulation of a regime with moderate scale separation

  14. Investigation of acoustic gravity waves created by anomalous heat sources: experiments and theoretical analysis

    Science.gov (United States)

    Pradipta, R.; Lee, M. C.

    2013-07-01

    We have been investigating high-power radio wave-induced acoustic gravity waves (AGWs) at Gakona, Alaska, using the High-frequency Active Aurora Research Program (HAARP) heating facility (i.e. HF heater) and extensive diagnostic instruments. This work was aimed at performing a controlled study of the space plasma turbulence triggered by the AGWs originating from anomalous heat sources, as observed in our earlier experiments at Arecibo, Puerto Rico (Pradipta 2007 MS Thesis MIT Press, Cambridge, MA). The HF heater operated in continuous wave (CW) O-mode can heat ionospheric plasmas effectively to yield a depleted magnetic flux tube as rising plasma bubbles (Lee et al 1998 Geophys. Res. Lett. 25 579). Two processes are responsible for the depletion of the magnetic flux tube: (i) thermal expansion and (ii) chemical reactions caused by heated ions. The depleted plasmas create large density gradients that can augment spread F processes via generalized Rayleigh-Taylor instabilities (Lee et al 1999 Geophys. Res. Lett. 26 37). It is thus expected that the temperature of neutral particles in the heated ionospheric region can be increased. Such a heat source in the neutral atmosphere may potentially generate AGWs in the form of traveling ionospheric plasma disturbances (TIPDs). We should point out that these TIPDs have features distinctively different from electric and magnetic field (ExB) drifts of HF wave-induced large-scale non-propagating plasma structures. Moreover, it was noted in our recent study of naturally occurring AGW-induced TIDs that only large-scale AGWs can propagate upward to reach higher altitudes. Thus, in our Gakona experiments we select optimum heating schemes for HF wave-induced AGWs that can be distinguished from the naturally occurring ones. The generation and propagation of AGWs are monitored by MUIR (Modular Ultra high-frequency Ionospheric Radar), Digisonde and GPS/low-earth-orbit satellites. Our theoretical and experimental studies have shown that

  15. Investigation of acoustic gravity waves created by anomalous heat sources: experiments and theoretical analysis

    International Nuclear Information System (INIS)

    We have been investigating high-power radio wave-induced acoustic gravity waves (AGWs) at Gakona, Alaska, using the High-frequency Active Aurora Research Program (HAARP) heating facility (i.e. HF heater) and extensive diagnostic instruments. This work was aimed at performing a controlled study of the space plasma turbulence triggered by the AGWs originating from anomalous heat sources, as observed in our earlier experiments at Arecibo, Puerto Rico (Pradipta 2007 MS Thesis MIT Press, Cambridge, MA). The HF heater operated in continuous wave (CW) O-mode can heat ionospheric plasmas effectively to yield a depleted magnetic flux tube as rising plasma bubbles (Lee et al 1998 Geophys. Res. Lett. 25 579). Two processes are responsible for the depletion of the magnetic flux tube: (i) thermal expansion and (ii) chemical reactions caused by heated ions. The depleted plasmas create large density gradients that can augment spread F processes via generalized Rayleigh–Taylor instabilities (Lee et al 1999 Geophys. Res. Lett. 26 37). It is thus expected that the temperature of neutral particles in the heated ionospheric region can be increased. Such a heat source in the neutral atmosphere may potentially generate AGWs in the form of traveling ionospheric plasma disturbances (TIPDs). We should point out that these TIPDs have features distinctively different from electric and magnetic field (ExB) drifts of HF wave-induced large-scale non-propagating plasma structures. Moreover, it was noted in our recent study of naturally occurring AGW-induced TIDs that only large-scale AGWs can propagate upward to reach higher altitudes. Thus, in our Gakona experiments we select optimum heating schemes for HF wave-induced AGWs that can be distinguished from the naturally occurring ones. The generation and propagation of AGWs are monitored by MUIR (Modular Ultra high-frequency Ionospheric Radar), Digisonde and GPS/low-earth-orbit satellites. Our theoretical and experimental studies have shown

  16. A study of Alfven's ionizing critical velocity

    International Nuclear Information System (INIS)

    Alfven's hypothesis of the ionizing critical velocity is investigated on the basis of observations with rotating plasma devices. The experimental fact is that the relative velocity between a neutral gas and a plasma perpendicular to a magnetic field does not exceed a critical velocity vc = √2eVi/m (eVi and m, the ionization energy and the atomic or molecular mass of the gas, respectively). It is interpreted from the standpoint of a current which generates in a process of plasma polarization. A final interpretation on the hypothesis is not given, but the structure and elementary process of the ionizing interaction is clarified. (author)

  17. Continuum damping of ideal toroidal Alfven eigenmodes

    International Nuclear Information System (INIS)

    A perturbation theory based on the two dimensional (2D) ballooning transform is systematically developed for ideal toroidal Alfven eigenmodes (TAEs). A formula, similar to the Fermi golden rule for decaying systems in quantum mechanics, is derived for the continuum damping rate of the TAE; the decay (damping) rate is expressed explicitly in terms of the coupling of the TAE to the continuum spectrum. Numerical results are compared with previous calculations. It is found that in some narrow intervals of the parameter mε the damping rate varies very rapidly. These regions correspond precisely to the root missing intervals of the numerical solution by Rosenbluth et al

  18. Unsteady Heat-Flux Measurements of Second-Mode Instability Waves in a Hypersonic Boundary Layer

    Science.gov (United States)

    Kergerise, Michael A.; Rufer, Shann J.

    2016-01-01

    In this paper we report on the application of the atomic layer thermopile (ALTP) heat- flux sensor to the measurement of laminar-to-turbulent transition in a hypersonic flat plate boundary layer. The centerline of the flat-plate model was instrumented with a streamwise array of ALTP sensors and the flat-plate model was exposed to a Mach 6 freestream over a range of unit Reynolds numbers. Here, we observed an unstable band of frequencies that are associated with second-mode instability waves in the laminar boundary layer that forms on the flat-plate surface. The measured frequencies, group velocities, phase speeds, and wavelengths of these instability waves are in agreement with data previously reported in the literature. Heat flux time series, and the Morlet-wavelet transforms of them, revealed the wave-packet nature of the second-mode instability waves. In addition, a laser-based radiative heating system was developed to measure the frequency response functions (FRF) of the ALTP sensors used in the wind tunnel test. These measurements were used to assess the stability of the sensor FRFs over time and to correct spectral estimates for any attenuation caused by the finite sensor bandwidth.

  19. Preferential heating of oxygen 5+ ions by finite-amplitude oblique Alfvén waves

    Science.gov (United States)

    Maneva, Yana G.; Viñas, Adolfo; Araneda, Jaime; Poedts, Stefaan

    2016-03-01

    Minor ions in the fast solar wind are known to have higher temperatures and to flow faster than protons in the interplanetary space. In this study we combine previous research on parametric instability theory and 2.5D hybrid simulations to study the onset of preferential heating of Oxygen 5+ ions by large-scale finite-amplitude Alfvén waves in the collisionless fast solar wind. We consider initially non-drifting isotropic multi-species plasma, consisting of isothermal massless fluid electrons, kinetic protons and kinetic Oxygen 5+ ions. The external energy source for the plasma heating and energization are oblique monochromatic Alfvén-cyclotron waves. The waves have been created by rotating the direction of initial parallel pump, which is a solution of the multi-fluid plasma dispersion relation. We consider propagation angles θ ≤ 30°. The obliquely propagating Alfvén pump waves lead to strong diffusion in the ion phase space, resulting in highly anisotropic heavy ion velocity distribution functions and proton beams. We discuss the application of the model to the problems of preferential heating of minor ions in the solar corona and the fast solar wind.

  20. Excitation and conversion of electromagnetic waves in pulsar magnetospheres

    OpenAIRE

    Gogoberidze, G.; Machabeli, G. Z.; V. V. Usov

    2007-01-01

    We demonstrate that nonlinear decay of obliquely propagating Langmuir waves into Langmuir and Alfven waves (L --> L'+A) is possible in a one-dimensional, highly relativistic, streaming, pair plasma. Such a plasma may be in the magnetospheres of pulsars. It is shown that the characteristic frequency of generated Alfven waves is much less than the frequency of Langmuir waves and may be consistent with the observational data on the radio emission of pulsars.

  1. Heat waves, intense droughts and desertification. summer 1994 in Southeast of Spain

    International Nuclear Information System (INIS)

    The South-East of spain, which has semiarid climate, is one of the hottest and dries areas in Europe. This region is specialized in irrigated agricultures and citrus fruits (lemons). the drought can last a long period, sometimes two or three years. The lack of water is becoming the biggest problem, especially since the development of irrigated cultures. Drought and heat waves are the major climatic risks and they cause most of the economic losses in agricultural activity. 1994 summer was exceptional in this region of Spain: heat waves and drought. A major disaster that revealed a crisis that began many years ago. The need of water is growing while the volume of available water tends to go down. 1994 summer and its disasters (fire, burnt crops by heat) generated social and politic tensions. Desertification is threatening the region. This situation is not new the drought is a normal phenomenon in a semiarid area, but the accumulation of drought, aridity and human actions worsening desertification. After 1994, new droughts and heat waves increased the lack of water because agriculture needs more and more water. Nonetheless this cultural method is compacting soil by the reduction of organic matter and by the heavy falls of rain. No solution has been found yet, they have to find new resources of water or change agricultural irrigation methods to save water and build up a sustainable development of this semiarid area. (Author) 12 refs.

  2. Development and Testing of a Refractory Millimeter-Wave Absorbent Heat Exchanger

    Science.gov (United States)

    Lambot, Thomas; Myrabo, Leik; Murakami, David; Parkin, Kevin

    2014-01-01

    Central to the Millimeter-Wave Thermal Launch System (MTLS) is the millimeter-wave absorbent heat exchanger. We have developed metallic and ceramic variants, with the key challenge being the millimeter-wave absorbent coatings for each. The ceramic heat exchanger came to fruition first, demonstrating for the first time 1800 K peak surface temperatures under illumination by a 110 GHz Gaussian beam. Absorption efficiencies of up to 80 are calculated for mullite heat exchanger tubes and up to 50 are calculated for alumina tubes. These are compared with estimates based on stratified layer and finite element analyses. The problem of how to connect the 1800 K end of the ceramic tubes to a graphite outlet manifold and nozzle is solved by press fitting, or by threading the ends of the ceramic tubes and screwing them into place. The problem of how to connect the ceramic tubes to a metallic or nylon inlet pipe is solved by using soft compliant PTFE and PVC tubes that accommodate thermal deformations of the ceramic tubes during startup and operation. We show the resulting heat exchangers in static tests using argon and helium as propellants.

  3. Bi-Directional Energy Cascades and the Origin of Kinetic Alfv\\'enic and Whistler Turbulence in the Solar Wind

    CERN Document Server

    Che, H; Viñas, A F

    2013-01-01

    The observed sub-proton scale turbulence spectrum in the solar wind raises the question of how that turbulence originates. Observations of keV energetic electrons during solar quite-time suggest them as possible source of free energy to drive the turbulence. Using particle-in-cell simulations, we explore how free energy in energetic electrons, released by an electron two-stream instability drives Weibel-like electromagnetic waves that excite wave-wave interactions. Consequently, both kinetic Alfv\\'enic and whistler waves are excited that evolve through inverse and forward magnetic energy cascades.

  4. A simple indicator to rapidly assess the short-term impact of heat waves on mortality within the French heat warning system

    Science.gov (United States)

    Antics, Annamaria; Pascal, Mathilde; Laaidi, Karine; Wagner, Vérène; Corso, Magali; Declercq, Christophe; Beaudeau, Pascal

    2013-01-01

    We propose a simple method to provide a rapid and robust estimate of the short-term impacts of heat waves on mortality, to be used for communication within a heat warning system. The excess mortality during a heat wave is defined as the difference between the observed mortality over the period and the observed mortality over the same period during the N preceding years. This method was tested on 19 French cities between 1973 and 2007. In six cities, we compared the excess mortality to that obtained using a modelling of the temperature-mortality relationship. There was a good agreement between the excess mortalities estimated by the simple indicator and by the models. Major differences were observed during the most extreme heat waves, in 1983 and 2003, and after the implementation of the heat prevention plan in 2006. Excluding these events, the mean difference between the estimates obtained by the two methods was of 13 deaths [1:45]. A comparison of mortality with the previous years provides a simple estimate of the mortality impact of heat waves. It can be used to provide early and reliable information to stakeholders of the heat prevention plan, and to select heat waves that should be further investigated.

  5. Air pollution during the 2003 European heat wave as seen by MOZAIC airliners

    Directory of Open Access Journals (Sweden)

    M. Tressol

    2007-11-01

    Full Text Available This study presents an analysis of both MOZAIC profiles above Frankfurt and Lagrangian dispersion model simulations for the 2003 European heat wave. The comparison of MOZAIC measurements in summer 2003 with the 11-year MOZAIC climatology reflects strong temperature anomalies (exceeding 4°C throughout the lower troposphere. Higher positive anomalies of temperature and negative anomalies of both wind speed and relative humidity are found for the period defined here as the heat wave (2–14 August 2003, compared to the periods before (16–31 July 2003 and after (16–31 August 2003 the heat wave. In addition, Lagrangian model simulations in backward mode indicate the suppressed long-range transport in the mid- to lower troposphere and the enhanced southern origin of air masses for all tropospheric levels during the heat wave. Ozone and carbon monoxide also present strong anomalies (both ~ +40 ppbv during the heat wave, with a maximum vertical extension reaching 6 km altitude around 11 August 2003. Pollution in the planetary boundary layer (PBL is enhanced during the day, with ozone mixing ratios two times higher than climatological values. This is due to a combination of factors, such as high temperature and radiation, stagnation of air masses and weak dry deposition, which favour the accumulation of ozone precursors and the build-up of ozone. A negligible role of a stratospheric-origin ozone tracer has been found for the lower troposphere in this study. From 29 July to 15 August 2003 forest fires burned around 0.3×106 ha in Portugal and added to atmospheric pollution in Europe. Layers with enhanced CO and NOy mixing ratios, probably advected from Portugal, were crossed by the MOZAIC aircraft in the free troposphere over Frankfurt. A series of forward and backward Lagrangian model simulations have been performed to investigate the origin of these anomalies. During the whole heat wave, European anthropogenic emissions

  6. Air pollution during the 2003 European heat wave as seen by MOZAIC airliners

    Directory of Open Access Journals (Sweden)

    M. Tressol

    2008-04-01

    Full Text Available This study presents an analysis of both MOZAIC profiles above Frankfurt and Lagrangian dispersion model simulations for the 2003 European heat wave. The comparison of MOZAIC measurements in summer 2003 with the 11-year MOZAIC climatology reflects strong temperature anomalies (exceeding 4°C throughout the lower troposphere. Higher positive anomalies of temperature and negative anomalies of both wind speed and relative humidity are found for the period defined here as the heat wave (2–14 August 2003, compared to the periods before (16–31 July 2003 and after (16–31 August 2003 the heat wave. In addition, Lagrangian model simulations in backward mode indicate the suppressed long-range transport in the mid- to lower troposphere and the enhanced southern origin of air masses for all tropospheric levels during the heat wave. Ozone and carbon monoxide also present strong anomalies (both ~+40 ppbv during the heat wave, with a maximum vertical extension reaching 6 km altitude around 11 August 2003. Pollution in the planetary boundary layer (PBL is enhanced during the day, with ozone mixing ratios two times higher than climatological values. This is due to a combination of factors, such as high temperature and radiation, stagnation of air masses and weak dry deposition, which favour the accumulation of ozone precursors and the build-up of ozone. A negligible role of a stratospheric-origin ozone tracer has been found for the lower troposphere in this study. From 29 July to 15 August 2003 forest fires burnt around 0.3×106 ha in Portugal and added to atmospheric pollution in Europe. Layers with enhanced CO and NOy mixing ratios, advected from Portugal, were crossed by the MOZAIC aircraft in the free troposphere over Frankfurt. A series of forward and backward Lagrangian model simulations have been performed to investigate the origin of anomalies during the whole heat wave. European anthropogenic emissions present the strongest

  7. Evaluation of approaches for modeling temperature wave propagation in district heating pipelines

    DEFF Research Database (Denmark)

    Gabrielaitiene, I.; Bøhm, Benny; Sunden, B.

    2008-01-01

    The limitations of a pseudo-transient approach for modeling temperature wave propagation in district heating pipes were investigated by comparing numerical predictions with experimental data. The performance of two approaches, namely a pseudo-transient approach implemented in the finite element...... that the fluid is represented as an ideal fluid. The approaches failed to adequately predict the temperature wave propagation in the case of rapid inlet temperature changes. The overall conclusion from this case study was that in order to improve the prediction of the transient temperature, attention...

  8. A survey of electron Bernstein wave heating and current drive potential for spherical tokamaks

    Czech Academy of Sciences Publication Activity Database

    Urban, Jakub; Decker, J.; Peysson, Y.; Preinhaelter, Josef; Shevchenko, V.; Taylor, G.; Vahala, L.; Vahala, G.

    2011-01-01

    Roč. 51, č. 8 (2011), 083050-083050. ISSN 0029-5515 R&D Projects: GA ČR GA202/08/0419; GA MŠk 7G10072 Institutional research plan: CEZ:AV0Z20430508 Keywords : spherical tokamak * electron Bernstein wave (EBW) * heating * current drive * electron cyclotron wave Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 4.090, year: 2011 http://iopscience.iop.org/0029-5515/51/8/083050/pdf/0029-5515_51_8_083050.pdf

  9. Dynamics of the thermal waves in THETA-pinch heated by α-particles

    International Nuclear Information System (INIS)

    The dynamics of thermal waves formation in THETA-pinch heated by α-particles with account for radiation and thermal conductivity is considered. By means of self-similar solutions obtained the parameters region is determined where the warm-up wave with increasing temperature is formed and the estimation of mass increase for the time of radiation cooling is made. In addition it is shown in the paper that all stationary solutions of thermal conductivity equation are unstable in relation to finite amplitude perturbations and the combustion process in used approximations is always nonstationary

  10. Ion Bernstein wave heating experiment on JIPPT-II-U device

    International Nuclear Information System (INIS)

    Ion Bernstein wave heating is investigated in the JIPPT-II-U tokamak plasma, n-bar sub(o) asymptoticaly equals 1.5 x 1013 cm-3, Tsub(eo) asymptoticaly equals 700 eV, and Tsub(io) = 300 eV for Psub(rf) 1-- 100 kW. In a two-ion-species helium-hydrogen plasma, the third harmonics of helium minority cyclotron resonance (deuterium-like) is heated. The background hydrogen ion temperature monitored by charge-exchange shows a significant rise, ΔTsub(i) 1-- 600 eV, when the helium harmonic resonance layer is placed near the center of the plasma. Typical observed hydrogen ion heating quality factor, ΔTsub(i)/Psub(rf)/n-barsub(o), is 1-- 10 eV/kW/1013cm-3. The dependence of ion heating efficiency on rf power, magnetic field and ion concentration is presented. (author)

  11. Changes in cause-specific mortality during heat waves in central Spain, 1975-2008

    Science.gov (United States)

    Miron, Isidro Juan; Linares, Cristina; Montero, Juan Carlos; Criado-Alvarez, Juan Jose; Díaz, Julio

    2015-09-01

    The relationship between heat waves and mortality has been widely described, but there are few studies using long daily data on specific-cause mortality. This study is undertaken in central Spain and analysing natural causes, circulatory and respiratory causes of mortality from 1975 to 2008. Time-series analysis was performed using ARIMA models, including data on specific-cause mortality and maximum and mean daily temperature and mean daily air pressure. The length of heat waves and their chronological number were analysed. Data were stratified in three decadal stages: 1975-1985, 1986-1996 and 1997-2008. Heat-related mortality was triggered by a threshold temperature of 37 °C. For each degree that the daily maximum temperature exceeded 37 °C, the percentage increase in mortality due to circulatory causes was 19.3 % (17.3-21.3) in 1975-1985, 30.3 % (28.3-32.3) in 1986-1996 and 7.3 % (6.2-8.4) in 1997-2008. The increase in respiratory cause ranged from 12.4 % (7.8-17.0) in the first period, to 16.3 % (14.1-18.4) in the second and 13.7 % (11.5-15.9) in the last. Each day of heat-wave duration explained 5.3 % (2.6-8.0) increase in respiratory mortality in the first period and 2.3 % (1.6-3.0) in the last. Decadal scale differences exist for specific-causes mortality induced by extreme heat. The impact on heat-related mortality by natural and circulatory causes increases between the first and the second period and falls significantly in the last. For respiratory causes, the increase is no reduced in the last period. These results are of particular importance for the estimation of future impacts of climate change on health.

  12. Self-consistent plasma heating and acceleration by strong magnetosonic waves for theta = 90 0. Part I: Basic mechanisms

    International Nuclear Information System (INIS)

    The behavior of strong magnetosonic waves propagating perpendicular to a static field B0 is investigated within the frequency range ω/sub c/i0 results; the electrons exhibit only poor heating associated with their adiabatic compression. The dynamics of both particle species, the consequences of the wave--particle energy transfer and the particle viscosities, are studied in detail. Competitive and self-consistent effects such as space-charge effects, wave overtaking, ion trapping, and wave damping are investigated and compared with previous models; the mechanisms by which these various phenomena interact on each other are analyzed. Characteristics of nonstochastic and stochastic ion heating are also discussed. Our computations show that if sufficient intensity is reached, one is not constrained to use lower-hybrid waves or cyclotron harmonic waves to heat a plasma efficiently and that any frequency below ω/sub lh/ can be used

  13. Using NASA Earth Science Datasets for National Climate Assessment Indicators: Urban Impacts of Heat Waves Associated with Climate Change

    Science.gov (United States)

    Sadoff, N.; Weber, S.; Zell, E. R.; de Sherbinin, A. M.

    2014-12-01

    Climate-induced heat waves have been increasing globally in the past 5-10 years and are projected to continue increasing throughout the 21st century. In urban areas, heat waves are exacerbated by the non-climate stressor of urban heat islands (UHIs). The vulnerability of a city's population to heat waves reflects exposure to extreme heat events, sensitivity of the population to impacts, such as adverse health effects, and adaptive capacity to prepare for and respond to heat waves. Socially and economically vulnerable populations are especially at risk to the impacts of heat waves, due to increasing energy costs, air pollution, and heat-related illness and mortality. NASA earth science datasets, combined with socioeconomic data, can be used to create indicators that characterize vulnerability to urban heat events and address the effectiveness of adaptation measures designed to reduce local temperatures. The indicator development process should include engagement from local stakeholders and end users from the onset to ensure local relevance and, ultimately, indicator uptake and sustainability. This presentation will explore the process of working with urban stakeholders in Philadelphia to develop a set of policy-relevant, interdisciplinary vulnerability indicators focused on extreme heat events in urban areas. Ambient and land surface temperature, land cover classifications, NDVI, and US Census data are used to create a basket of indicators that reflect urban heat wave duration and intensity, UHI exposure, socioeconomic vulnerability, and adaptation effectiveness. These indicators can be assessed at the city level and also comparatively among different parts of a city to help quantify and track heat wave impacts on vulnerable populations and the effectiveness of adaptation measures.

  14. A model of non-homogeneous damped electromagnetic wave and heat equation in ferrite materials

    CERN Document Server

    Tung, M J; Hsu, C H; Tseng, T Y

    2002-01-01

    This study uses a closely coupled model to treat the core loss of ferrite by the combination of non-homogeneous damped electromagnetic wave and heat equation. The heat dissipation of ferrites is caused by the core loss, which is a summation of magnetic, dielectric and eddy current losses. Explicit finite difference method solves the coupled equations to calculate core loss and compares it with the measured results. Those results show that this method can be used to analyze electromagnetic and thermal field with temperature dependence of ferrites.

  15. Characteristics of recent heat waves in Korea and their policy implications

    Czech Academy of Sciences Publication Activity Database

    Kim, J.; Kim, B.; J.; Park, S.; Y.; Kyselý, Jan

    Wonju: NIMR (National Institute of Meteorological Administration/ KMA), IAP (Institute of Atmospheric Physics/ CAS), 2008, s. 16-22. ISBN N. [NIMR-IAP Joint Research Workshop /8./. Wonju (KR), 05.11.2008-06.11.2008] R&D Projects: GA ČR GC205/07/J044 Grant ostatní: KMA's Research and Development Program(KR) Metri-2008-B-10; Korea Research Foundation(KR) KRF-2006-C00005 Institutional research plan: CEZ:AV0Z30420517 Keywords : heat wave * excessive heat warning * mortality * South Korea Subject RIV: DG - Athmosphere Sciences, Meteorology

  16. Ion cyclotron heating mechanism of fast magnetosonic wave in the TNT-A tokamak

    International Nuclear Information System (INIS)

    Ion heating mechanism of fast magnetosonic wave in the ion cyclotron range of frequency (ICRF) has been studied in the TNT-A tokamak. Ion temperature measurements have been made with mass separated neutral particle analyser. The effects of the fundamental proton cyclotron resonance layer (ICR) and the two-ion hybrid resonance layer (HBR) on ion heating are observed. In the case of hydrogen minority (ICR and HBR in the plasma), where the ratio of hydrogen-to-deuterium concentration, nH/nD, is 0.05, the increase in hydrogen temperature is larger than that in deuterium, and most of RF power is absorbed by hydrogen. (author)

  17. Non-resonant nonlinear coupling of magnetohydrodynamic waves in inhomogeneous media

    CERN Document Server

    Nakariakov, V M; Arber, T D

    2001-01-01

    A new mechanism for the enhanced generation of compressible fluctuations by Alfven waves is presented. A strongly nonlinear regime of Alfven wave phase-mixing is numerically simulated in a one-dimensionally inhomogeneous plasma of finite temperature. It is found that the inhomogeneity of the medium determines the efficiency of nonlinear excitation of magnetoacoustic waves. The level of the compressible fluctuations is found to be higher (up to the factor of two) in inhomogeneous regions. The amplitude of the generated magnetoacoustic wave can reach up to 30% of the source Alfven wave amplitude, and this value is practically independent of the Alfven wave amplitude and the steepness of Alfven speed profile. The highest amplitudes of compressible disturbances are reached in plasmas with beta of about 0.5. The further growth of the amplitude of compressible fluctuations is depressed by saturation.

  18. Overly persistent circulation in climate models contributes to overestimated frequency and duration of heat waves and cold spells

    Science.gov (United States)

    Plavcová, Eva; Kyselý, Jan

    2016-05-01

    The study examines links of summer heat waves and winter cold spells in Central Europe to atmospheric circulation and specifically its persistence in an ensemble of regional climate models (RCMs). We analyse 13 RCMs driven by the ERA-40 reanalysis and compare them against observations over reference period 1971-2000. Using objective classification of circulation types and an efficiency coefficient with a block resampling test, we identify circulation types significantly conducive to heat waves and cold spells. We show that the RCMs have a stronger tendency to group together days with very high or low temperature and tend to simulate too many heat waves and cold spells, especially those lasting 5 days and more. Circulation types conducive to heat waves in summer are characterized by anticyclonic, southerly and easterly flow, with increasing importance of warm advection during heat waves. Winter cold spells are typically associated with easterly and anticyclonic flow, and the onset of cold spells tends to be linked to northerly and cyclonic flow with cold advection. The RCMs are generally able to reproduce the links between circulation and heat waves or cold spells, including the radiation-to-advection effect for heat waves and the opposite advection-to-radiation effect for cold spells. They capture relatively well also changes of mean temperature anomalies during sequences of given circulation types, namely the tendency towards temperature increase (decrease) during those types conducive to heat waves (cold spells). Since mean lengths of all circulation supertypes are overestimated in the RCMs, we conclude that the overly persistent circulation in climate models contributes to the overestimated frequency of long heat waves and cold spells. As these biases are rather general among the examined RCMs and similar drawbacks are likely to be manifested in climate model simulations for the twenty-first century, the results also suggest that climate change scenarios for

  19. Effect of heat wave at the initial stage in spark plasma sintering.

    Science.gov (United States)

    Zhang, Long; Zhang, Xiaomin; Chu, Zhongxiang; Peng, Song; Yan, Zimin; Liang, Yuan

    2016-01-01

    Thermal effects are important considerations at the initial stage in spark plasma sintering of non-conductive Al2O3 powders. The generalized thermo-elastic theory is introduced to describe the influence of the heat transport and thermal focusing caused by thermal wave propagation within a constrained space and transient time. Simulations show that low sintering temperature can realize high local temperature because of the superposition effect of heat waves. Thus, vacancy concentration differences between the sink and the cross section of the particles increase relative to that observed during pressure-less and hot-pressure sintering. Results show that vacancy concentration differences are significantly improved during spark plasma sintering, thereby decreasing the time required for sintering. PMID:27386287

  20. Generation of Artificial Acoustic-Gravity Waves and Traveling Ionospheric Disturbances in HF Heating Experiments

    Science.gov (United States)

    Pradipta, R.; Lee, M. C.; Cohen, J. A.; Watkins, B. J.

    2015-10-01

    We report the results of our ionospheric HF heating experiments to generate artificial acoustic-gravity waves (AGW) and traveling ionospheric disturbances (TID), which were conducted at the High-frequency Active Auroral Research Program facility in Gakona, Alaska. Based on the data from UHF radar, GPS total electron content, and ionosonde measurements, we found that artificial AGW/TID can be generated in ionospheric modification experiments by sinusoidally modulating the power envelope of the transmitted O-mode HF heater waves. In this case, the modulation frequency needs to be set below the characteristic Brunt-Vaisala frequency at the relevant altitudes. We avoided potential contamination from naturally-occurring AGW/TID of auroral origin by conducting the experiments during geomagnetically quiet time period. We determine that these artificial AGW/TID propagate away from the edge of the heated region with a horizontal speed of approximately 160 m/s.