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  • 1
    Electronic Resource
    Electronic Resource
    Alfvénic waves and alignment of large grains (1994)
    Springer
    Astrophysics and space science 216 (1994), S. 235-237 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The alignment of grains under the influence of the Alfvenic waves is discussed. It is shown that even small deviations from grain uniformity result in the alignment of large (l 〉 6⋅10−5 cm) grains. The latter result is important for the interpretation of the IR polarization data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00982499
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A statistical description of astrophysical turbulence (1994)
    Springer
    Astrophysics and space science 216 (1994), S. 207-212 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The properties of the ISM indicate that it is turbulent. However, the ISM turbulence is radically different from that in incompressible fluids. That is why it is so important to study it through observations. The relevant study still poses a challenging problem. In the present paper recent results based on a statistical approach to the problem are surveyed. Although it was pointed out long ago (see Kaplanet al., 1970) that random 3D motions of the ISM gas result in fluctuations of the observed electromagnetic emission, it is only recently that the problem of recovering statistical properties of the ISM turbulence from the line integrated data was given an adequate mathematical treatment. Here by the example of studying turbulence in HI, it is shown that the inverse problem can be solved uniquely using a realistic model of the ISM. The application of theoretical conclusions to existing data explains some facts which used to be considered inconsistent with turbulent behaviour and reveals unexpected features of the ISM turbulence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00982495
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  • 3
    Electronic Resource
    Electronic Resource
    Hierarchial galactic dynamo and seed magnetic field problem (1994)
    Springer
    Astrophysics and space science 216 (1994), S. 219-221 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new approach to the galactic seed magnetic field problem is briefly discussed. It is shown that, in early stages of galactic evolution, the hierarchial agglomeration and fragmentation processes can account for the generation of a dynamically important magnetic field. The amplification of this field follows an inverse cascade since a non-zero average value of the field amplified on a smaller scale serves as a seed field on the next (earlier) hierarchial scale. In such a scenario, a problem of how to get things started never occurs as any infinitesimally small battery generated seed field (Lazarian 1992a) can be efficiently amplified passing by through a sufficient number of amplification cascades.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00982497
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  • 4
    Electronic Resource
    Electronic Resource
    Experimental study of 3D turbulence by solving an inverse problem (1993)
    Springer
    Flow, turbulence and combustion 51 (1993), S. 191-195 
    Details
    ISSN: 1573-1987
    Keywords: turbulence ; inverse problem ; statistical method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The problem of the investigation of 3D turbulence from the projected data is studied here. It is shown that statistical information about turbulence can be recovered in such situations through a solution of an inverse problem. Unlike earlier papers, the adopted model of the turbulence envisages the turbulence characteristics to vary inside the 3D volume. Analytical solutions expressing turbulence characteristics (correlation functions, spectra) in terms of experimental data are found for this realistic model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01082536
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  • 5
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    Particle Acceleration in Turbulence and Weakly Stochastic Reconnection (2012)
    American Physical Society
    Details
    Publication Date: 2012-06-15
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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  • 6
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    Scattering of Cosmic Rays by Magnetohydrodynamic Interstellar Turbulence (2002)
    American Physical Society
    Details
    Publication Date: 2002-12-27
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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  • 7
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    Compressible Sub-Alfvénic MHD Turbulence in Low-βPlasmas (2002)
    American Physical Society
    Details
    Publication Date: 2002-05-31
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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  • 8
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    Stochastic reacceleration of relativistic electrons by turbulent reconnection: a mechanism for cluster-scale radio emission? (2016)
    Oxford University Press
    Details
    Publication Date: 2016-03-24
    Description: In this paper, we investigate a situation where relativistic particles are reaccelerated diffusing across regions of reconnection and magnetic dynamo in super-Alfvenic, incompressible large-scale turbulence. We present an exploratory study of this mechanism in the intracluster medium (ICM). In view of large-scale turbulence in the ICM, we adopt a reconnection scheme that is based on turbulent reconnection and magnetohydrodynamics (MHD) turbulence. In this case, particles are accelerated and decelerated in a systematic way in reconnecting and magnetic-dynamo regions, respectively, and on longer time-scales undergo a stochastic process diffusing across these sites (similar to second-order Fermi ). Our study extends on larger scales numerical studies that focused on the acceleration in and around turbulent reconnecting regions. We suggest that this mechanism may play a role in the reacceleration of relativistic electrons in galaxy clusters providing a new physical scenario to explain the origin of cluster-scale diffuse radio emission. Indeed differently from current turbulent reacceleration models proposed for example for radio haloes, this mechanism is based on the effect of large-scale incompressible and super-Alfvenic turbulence. In this new model, turbulence governs the interaction between relativistic particles and magnetic field lines that diffuse, reconnect and are stretched in the turbulent ICM.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 9
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    Extending velocity channel analysis for studying turbulence anisotropies (2016)
    Oxford University Press
    Details
    Publication Date: 2016-07-06
    Description: We extend the velocity channel analysis (VCA), introduced by Lazarian & Pogosyan, of the intensity fluctuations in the velocity slices of position–position–velocity (PPV) spectroscopic data from Doppler broadened lines to study statistical anisotropy of the underlying velocity and density that arises in a turbulent medium from the presence of magnetic field. In particular, we study analytically how the anisotropy of the intensity correlation in the channel maps changes with the thickness of velocity channels. In agreement with the earlier VCA studies, we find that the anisotropy in the thick channels reflects the anisotropy of the density field, while the relative contribution of density and velocity fluctuations to the thin velocity channels depends on the density spectral slope. We show that the anisotropies arising from Alfvén, slow and fast magnetohydrodynamical modes are different; in particular, the anisotropy in PPV created by fast modes is opposite to that created by Alfvén and slow modes, and this can be used to separate their contributions. We successfully compare our results with the recent numerical study of the PPV anisotropies measured with synthetic observations. We also extend our study to the medium with self-absorption as well as to the case of absorption lines. In addition, we demonstrate how the studies of anisotropy can be performed using interferometers.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 10
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    Limits on the ion temperature anisotropy in the turbulent intracluster medium (2016)
    Oxford University Press
    Details
    Publication Date: 2016-06-15
    Description: Turbulence in the weakly collisional intracluster medium (ICM) of galaxies is able to generate strong thermal velocity anisotropies in the ions (with respect to the local magnetic field direction), if the magnetic moment of the particles is conserved in the absence of Coulomb collisions. In this scenario, the anisotropic pressure magnetohydrodynamic (AMHD) turbulence shows a very different statistical behaviour from the standard MHD one and is unable to amplify seed magnetic fields. This is in contrast to previous cosmological MHD simulations that are successful in explaining the observed magnetic fields in the ICM. On the other hand, temperature anisotropies can also drive plasma instabilities that can relax the anisotropy. This work aims to compare the relaxation rate with the growth rate of the anisotropies driven by the turbulence. We employ quasi-linear theory to estimate the ion scattering rate resulting from the parallel firehose, mirror and ion-cyclotron instabilities, for a set of plasma parameters resulting from AMHD simulations of the turbulent ICM. We show that the ICM turbulence can sustain only anisotropy levels very close to the instability thresholds. We argue that the AMHD model that bounds the anisotropies at the marginal stability levels can describe the Alfvénic turbulence cascade in the ICM.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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