umu.sePublikationer
Ändra sökning
Avgränsa sökresultatet
1 - 16 av 16
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1. Adhikary, N C
    et al.
    Misra, Amar P
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Bailung, H
    Chutia, J
    Ion-beam driven dust ion-acoustic solitary waves in dusty plasmas2010Ingår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 17, nr 4, artikel-id 044502Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The nonlinear propagation of small but finite amplitude dust ion-acoustic waves (DIAWs) in an ion-beam driven plasma consisting of Boltzmannian electrons, positive ions, and stationary negatively charged dust grains is studied by using the standard reductive perturbation technique. It is shown that there exist two critical values (γc1) and (γc2) of ion beam to ion phase velocity ratio (γ), above and below which the beam generated solitons are not possible. The effects of the parameters, namely, γ, the ratio of the ion beam to plasma ion density (μi), the dust to ion density ratio (μd), and the ion beam to plasma ion mass ratio (μ) on both the amplitude and width of the stationary DIAWs, are analyzed numerically, and applications of the results to laboratory ion beam as well as space plasmas (e.g., auroral plasmas) are explained.

  • 2. Bains, AS
    et al.
    Misra, Amar P
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Saini, NS
    Gill, TS
    Modulational instability of ion-acoustic wave envelopes in magnetized quantum electron-positron-ion plasmas2010Ingår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 17, nr 1, artikel-id 012103Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The amplitude modulation of quantum ion-acoustic waves (QIAWs) along an external magnetic field is studied in a quantum electron-positron-ion (e-p-i) magnetoplasma. Reductive perturbation technique is used to derive the three-dimensional nonlinear Schroumldinger equation which governs the slow modulation of QIAW packets. Accounting for the effects of the electron to ion number density ratio (mu), the normalized ion-cyclotron frequency (omega(c)) as well as the ratio (H) of the "plasmonic energy density" to the Fermi energy, new regimes for the modulational instability of QIAWs are obtained and analyzed. In contrast to one-dimensional unmagnetized e-p-i plasmas, the instability growth rate is shown to suppress with increasing mu or decreasing the values of H. The predicted results could be important for understanding the salient features of modulated QIAW packets in dense astrophysical plasmas as well as to the next generation intense laser solid density plasma experiments.

  • 3. Banerjee, S
    et al.
    Misra, Amar P
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Shukla, P K
    Rondoni, L
    Spatiotemporal chaos and the dynamics of coupled Langmuir and ion-acoustic waves in plasmas2010Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 81, nr 4, artikel-id 046405Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A simulation study is performed to investigate the dynamics of coupled Langmuir waves (LWs) and ion-acoustic waves (IAWs) in an unmagnetized plasma. The effects of dispersion due to charge separation and the density nonlinearity associated with the IAWs are considered to modify the properties of Langmuir solitons, as well as to model the dynamics of relatively large amplitude wave envelopes. It is found that the Langmuir wave electric field, indeed, increases by the effect of ion-wave nonlinearity (IWN). Use of a low-dimensional model, based on three Fourier modes, shows that a transition to temporal chaos is possible, when the length scale of the linearly excited modes is larger than that of the most unstable ones. The chaotic behaviors of the unstable modes are identified by the analysis of Lyapunov exponent spectra. The space-time evolution of the coupled LWs and IAWs shows that the IWN can cause the excitation of many unstable harmonic modes and can lead to strong IAW emission. This occurs when the initial wave field is relatively large or the length scale of IAWs is larger than the soliton characteristic size. Numerical simulation also reveals that many solitary patterns can be excited and generated through the modulational instability of unstable harmonic modes. As time goes on, these solitons are seen to appear in the spatially partial coherence state due to the free ion-acoustic radiation as well as in the state of spatiotemporal chaos due to collision and fusion in the stochastic motion. The latter results in the redistribution of initial wave energy into a few modes with small length scales, which may lead to the onset of Langmuir turbulence in laboratory as well as space plasmas.

  • 4. Banerjee, S.
    et al.
    Rondoni, L.
    Mukhopadhyay, S.
    Misra, Amar P
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Synchronization of spatiotemporal semiconductor lasers and its application in color image encryption2011Ingår i: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 284, nr 9, s. 2278-2291Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Optical chaos is a topic of current research characterized by high-dimensional nonlinearity which is attributed to the delay-induced dynamics, high bandwidth and easy modular implementation of optical feedback. In light of these facts, which add enough confusion and diffusion properties for secure communications, we explore the synchronization phenomena in spatiotemporal semiconductor laser systems. The novel system is used in a two-phase colored image encryption process. The high-dimensional chaotic attractor generated by the system produces a completely randomized chaotic time series, which is ideal in the secure encoding of messages. The scheme thus illustrated is a two-phase encryption method, which provides sufficiently high confusion and diffusion properties of chaotic cryptosystem employed with unique data sets of processed chaotic sequences. In this novel method of cryptography, the chaotic phase masks are represented as images using the chaotic sequences as the elements of the image. The scheme drastically permutes the positions of the picture elements. The next additional layer of security further alters the statistical information of the original image to a great extent along the three-color planes. The intermediate results during encryption demonstrate the infeasibility for an unauthorized user to decipher the cipher image. Exhaustive statistical tests conducted validate that the scheme is robust against noise and resistant to common attacks due to the double shield of encryption and the infinite dimensionality of the relevant system of partial differential equations.

  • 5. Banerjee, Santo
    et al.
    Misra, Amar P
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rondoni, L.
    Spatiotemporal evolution in a (2+1)-dimensional chemotaxis model2012Ingår i: Physica A: Statistical Mechanics and its Applications, ISSN 0378-4371, E-ISSN 1873-2119, Vol. 391, nr 1-2, s. 107-112Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Simulations are performed to investigate the nonlinear dynamics of a (2 + 1)-dimensional chemotaxis model of Keller-Segel (KS) type, with a logistic growth term. Because of its ability to display auto-aggregation, the KS model has been widely used to simulate self-organization in many biological systems. We show that the corresponding dynamics may lead to steady-states, to divergencies in a finite time as well as to the formation of spatiotemporal irregular patterns. The latter, in particular, appears to be chaotic in part of the range of bounded solutions, as demonstrated by the analysis of wavelet power spectra. Steady-states are achieved with sufficiently large values of the chemotactic coefficient (chi) and/or with growth rates r below a critical value r(c). For r > r(c), the solutions of the differential equations of the model diverge in a finite time. We also report on the pattern formation regime, for different values of chi, r and of the diffusion coefficient D. (C) 2011 Elsevier B.V. All rights reserved.

  • 6.
    Brodin, Gert
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Misra, Amar P
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Marklund, Mattias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Spin contribution to the ponderomotive force in a plasma2010Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 105, nr 10, s. 105004-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The concept of a ponderomotive force due to the intrinsic spin of electrons is developed. An expression containing both the classical as well as the spin-induced ponderomotive force is derived. The results are used to demonstrate that an electromagnetic pulse can induce a spin-polarized plasma. Furthermore, it is shown that, for certain parameters, the nonlinear backreaction on the electromagnetic pulse from the spin magnetization current can be larger than that from the classical free current. Suitable parameter values for a direct test of this effect are presented.

  • 7.
    Misra, Amar P
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Banerjee, S.
    Upper-hybrid wave-driven Alfvenic turbulence in magnetized dusty plasmas2011Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 83, nr 3, artikel-id 037401Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The nonlinear dynamics of coupled electrostatic upper-hybrid (UH) and Alfven waves (AWs) is revisited in a magnetized electron-ion plasma with charged dust impurities. A pair of nonlinear equations that describe the interaction of UH wave envelopes (including the relativistic electron mass increase) and the density as well as the compressional magnetic field perturbations associated with the AWs are solved numerically to show that many coherent solitary patterns can be excited and saturated due to modulational instability of unstable UH waves. The evolution of these solitary patterns is also shown to appear in the states of spatiotemporal coherence, temporal as well as spatiotemporal chaos, due to collision and fusion among the patterns in stochastic motion. Furthermore, these spatiotemporal features are demonstrated by the analysis of wavelet power spectra. It is found that a redistribution of wave energy takes place to higher harmonic modes with small wavelengths, which, in turn, results in the onset of Alfvenic turbulence in dusty magnetoplasmas. Such a scenario can occur in the vicinity of Saturn's magnetosphere as many electrostatic solitary structures have been observed there by the Cassini spacecraft.

  • 8.
    Misra, Amar P
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Banerjee, S
    Haas, F
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Shukla, P K
    Assis, L P G
    Temporal dynamics in the one-dimensional quantum Zakharov equations for plasmas2010Ingår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 17, nr 3, artikel-id 032307Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The temporal dynamics of the quantum Zakharov equations in one spatial dimension, which describes the nonlinear interaction of quantum Langmuir waves and quantum ion-acoustic waves, is revisited by considering their solution as a superposition of three interacting wave modes in Fourier space. Previous results in the literature are modified and rectified. Periodic, chaotic, and hyperchaotic behaviors of the Fourier-mode amplitudes are identified by the analysis of Lyapunov exponent spectra and the power spectrum. The periodic route to chaos is explained through a one-parameter bifurcation analysis. The system is shown to be destabilized via a supercritical Hopf-bifurcation. The adiabatic limits of the fully spatiotemporal and reduced systems are compared from the viewpoint of integrability properties.

  • 9.
    Misra, Amar P
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Brodin, Gert
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Marklund, Mattias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Shukla, Padma K
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Circularly polarized modes in magnetized spin plasmas2010Ingår i: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, ISSN 0022-3778, Vol. 76, nr 3/4, s. 857-864Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of the intrinsic spin of electrons on the propagation of circularly polarized waves in a magnetized plasma is considered. New eigenmodes are identified, one of which propagates below the electron cyclotron frequency, one above the spin-precession frequency, and another close to the spin-precession frequency. The latter corresponds to the spin modes in ferromagnets under certain conditions. In the non-relativistic motion of electrons, the spin effects become noticeable even when the external magnetic field B0 is below the quantum critical magnetic field strength, i.e. B0 < BQ = 4.4138 × 109T and the electron density satisfies n0nc ≃ 1032m−3. The importance of electron spin (paramagnetic) resonance (ESR) for plasma diagnostics is discussed.

  • 10.
    Misra, Amar P
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Brodin, Gert
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Marklund, Mattias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Shukla, Padma K
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Generation of wakefields by whistlers in spin quantum magnetoplasmas2010Ingår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 17, nr 12, artikel-id 122306Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The excitation of electrostatic wakefields in a magnetized spin quantum plasma by the classical and the spin-induced ponderomotive force (CPF and SPF, respectively) due to whistler waves is reported. The nonlinear dynamics of the whistlers and the wakefields is shown to be governed by a coupled set of nonlinear Schrodinger and driven Boussinesq-like equations. It is found that the quantum force associated with the Bohm potential introduces two characteristic length scales, which lead to the excitation of multiple wakefields in a strongly magnetized dense plasma (with a typical magnetic field strength B(0)greater than or similar to 10(9) T and particle density n(0)greater than or similar to 10(36) m(-3)), where the SPF strongly dominates over the CPF. In other regimes, namely, B(0)less than or similar to 10(8) T and n(0)less than or similar to 10(35) m(-3), where the SPF is comparable to the CPF, a plasma wakefield can also be excited self-consistently with one characteristic length scale. Numerical results reveal that the wakefield amplitude is enhanced by the quantum tunneling effect; however, it is lowered by the external magnetic field. Under appropriate conditions, the wakefields can maintain high coherence over multiple plasma wavelengths and thereby accelerate electrons to extremely high energies. The results could be useful for particle acceleration at short scales, i.e., at nanometer and micrometer scales, in magnetized dense plasmas where the driver is the whistler wave instead of a laser or a particle beam.

  • 11.
    Misra, Amar P
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Brodin, Gert
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Marklund, Mattias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Shukla, Padma K
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Localized whistlers in magnetized spin quantum plasmas2010Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 82, s. 056406-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The nonlinear propagation of electromagnetic (EM) electron-cyclotron waves (whistlers) along an external magnetic field, and their modulation by electrostatic small but finite amplitude ion-acoustic density perturbations are investigated in a uniform quantum plasma with intrinsic spin of electrons. The effects of the quantum force associated with the Bohm potential and the combined effects of the classical as well as the spin-induced ponderomotive forces (CPF and SPF, respectively) are taken into consideration. The latter modify the local plasma density in a self-consistent manner. The coupled modes of wave propagation is shown to be governed by a modified set of nonlinear Schrödinger-Boussinesq-like equations which admit exact solutions in form of stationary localized envelopes. Numerical simulation reveals the existence of large-scale density fluctuations that are self-consistently created by the localized whistlers in a strongly magnetized high density plasma. The conditions for the modulational instability (MI) and the value of its growth rate are obtained. Possible applications of our results, e.g., in strongly magnetized dense plasmas and in the next generation laser-solid density plasma interaction experiments are discussed.

  • 12.
    Misra, Amar P
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Marklund, Mattias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Brodin, Gert
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Shukla, Padma K
    RUB International Chair, International Centre for Advanced Studies in Physical Sciences, Faculty of Physics and Astronomy, Ruhr University Bochum, Bochum, Germany.
    Stability of two-dimensional ion-acoustic wave packets in quantum plasmas2011Ingår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 18, nr 4, s. 042102-042109Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The nonlinear propagation of two-dimensional (2D) quantum ion-acoustic waves (QIAWs) is studied in a quantum electron–ion plasma. By using a 2D quantum hydrodynamic model and the method of multiple scales, a new set of coupled nonlinear partial differential equations is derived which governs the slow modulation of the 2D QIAW packets. The oblique modulational instability (MI) is then studied by means of a corresponding nonlinear Schrödinger equation derived from the coupled nonlinear partial differential equations. It is shown that the quantum parameter H (ratio of the plasmon energy density to Fermi energy) shifts the MI domains around the kθ -plane, where k is the carrier wave number and θ is the angle of modulation. In particular, the ion-acoustic wave (IAW), previously known to be stable under parallel modulation in classical plasmas, is shown to be unstable in quantum plasmas. The growth rate of the MI is found to be quenched by the obliqueness of modulation. The modulation of 2D QIAW packets along the wave vector k is shown to be described by a set of Davey–Stewartson-like equations. The latter can be studied for the 2D wave collapse in dense plasmas. The predicted results, which could be important to look for stable wave propagation in laboratory experiments as well as in dense astrophysical plasmas, thus generalize the theory of MI of IAW propagations both in classical and quantum electron–ion plasmas.

  • 13.
    Misra, Amar P
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Department of Mathematics, Siksha Bhavana, Visva-Bharati University, India.
    Samanta, S
    Double-layer shocks in a magnetized quantum plasma2010Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 82, nr 3, artikel-id 037401Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The formation of small but finite amplitude electrostatic shocks in the propagation of quantum ion-acoustic waves obliquely to an external magnetic field is reported in a quantum electron-positron-ion plasma. Such shocks are seen to have double-layer (DL) structures composed of the compressive and accompanying rarefactive slow-wave fronts. Existence of such DL shocks depends critically on the quantum coupling parameter H associated with the Bohm potential and the positron to electron density ratio delta. The profiles may, however, steepen initially and reach a steady state with a number of solitary waves in front of the shocks. Such novel DL shocks could be a good candidate for particle acceleration in intense laser-solid density plasma interaction experiments as well as in compact astrophysical objects, e.g., magnetized white dwarfs.

  • 14.
    Misra, Amar P
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Shukla, PK
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Nonlinear wave-wave interactions in quantum plasmas2010Ingår i: New frontiers in advanced plasma physics, American Institute of Physics (AIP), 2010, s. 103-110Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wave-wave interaction in plasmas is a topic of important research since the 16th century. The formation of Langmuir solitons through the coupling of high-frequency (hf) Langmuir and low-frequency (If) ion-acoustic waves, is one of the most interesting features in the context of turbulence in modern plasma physics. Moreover, quantum plasmas, which are ubiquitous in ultrasmall electronic devices, micromechanical systems as well as in dense astrophysical environments are a topic of current research. In the light of notable interests in such quantum plasmas, we present here a theoretical investigation on the nonlinear interaction of quantum Langmuir waves (QLWs) and quantum ion-acoustic waves (QIAWs), which are governed by the one-dimensional quantum Zakharov equations (QZEs). It is shown that a transition to spatiotemporal chaos (STC) occurs when the length scale of excitation of linear modes is larger than that of the most unstable ones. Such length scale is, however, to be larger (compared to the classical one) in presence of the quantum tunneling effect. The latter induces strong QIAW emission leading to the occurrence of collision and fusion among the patterns at an earlier time than the classical case. Moreover, numerical simulation of the QZEs reveals that many solitary patterns can be excited and saturated through the modulational instability (MI) of unstable harmonic modes. In a longer time, these solitons are seen to appear in the state of STC due to strong QIAW emission as well as by the collision and fusion in stochastic motion. The energy in the system is thus strongly redistributed, which may switch on the onset of Langmuir turbulence in quantum plasmas.

  • 15.
    Misra, Amar Prasad
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Shukla, Padma Kant
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Modulational instability and nonlinear evolution of two-dimensional electrostatic wave packets in ultra-relativistic degenerate dense plasmas2011Ingår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 18, nr 4, artikel-id 042308Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We consider the nonlinear propagation of electrostatic wave packets in an ultra-relativistic (UR) degenerate dense electron-ion plasma, whose dynamics is governed by the nonlocal two-dimensional nonlinear Schrodinger-like equations. The coupled set of equations is then used to study the modulational instability (MI) of a uniform wave train to an infinitesimal perturbation of multidimensional form. The condition for the MI is obtained, and it is shown that the nondimensional parameter, beta proportional to lambda(C)n(0)(1/3) (where lambda(C) is the reduced Compton wavelength and n(0) is the particle number density) associated with the UR pressure of degenerate electrons, shifts the stable (unstable) regions at n(0) similar to 10(30)cm(-3) to unstable (stable) ones at higher densities, i.e., n(0) greater than or similar to 7 x 10(33). It is also found that the higher the values of n(0), the lower is the growth rate of MI with cut-offs at lower wave numbers of modulation. Furthermore, the dynamical evolution of the wave packets is studied numerically. We show that either they disperse away or they blowup in a finite time, when the wave action is below or above the threshold. The results could be useful for understanding the properties of modulated wave packets and their multidimensional evolution in UR degenerate dense plasmas, such as those in the interior of white dwarfs and/or pre-Supernova stars.

  • 16.
    Stefan, Martin
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zamanian, Jens
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Brodin, Gert
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Misra, Amar P
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Marklund, Mattias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ponderomotive force due to the intrinsic spin in extended fluid and kinetic models2011Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 83, nr 3, s. 036410-036416Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper we calculate the contribution to the ponderomotive force in a plasma from the electron spin using a recently developed model. The spin-fluid model used in the present paper contains spin-velocity correlations, in contrast to previous models used for the same purpose. Is its then found that previous terms for the spin-ponderomotive force are recovered, but also that additional terms appear. Furthermore, the results due to the spin-velocity correlations are confirmed using the spin-kinetic theory. The significance of our results is discussed.

1 - 16 av 16
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf