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B. Bavassano - One of the best experts on this subject based on the ideXlab platform.
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The Energy Cascade in Solar Wind MHD Turbulence
Earth Moon and Planets, 2009Co-Authors: Raffaele Marino, Luca Sorriso-valvo, Vincenzo Carbone, Alain Noullez, Roberto Bruno, B. BavassanoAbstract:Direct evidence for the presence of an inertial Energy Cascade, the most characteristic signature of hydromagnetic turbulence (MHD), is observed in the solar wind by the Ulysses spacecraft. A linear relation is indeed observed for the scaling of mixed third order structure functions involving Elsasser variables. This experimental result, confirming the prescription stemming from a theorem for MHD turbulence, firmly establishes the turbulent character of low-frequency velocity and magnetic field fluctuations in the solar wind plasma.
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heating the solar wind by a magnetohydrodynamic turbulent Energy Cascade
The Astrophysical Journal, 2008Co-Authors: Raffaele Marino, Vincenzo Carbone, Alain Noullez, Roberto Bruno, L Sorrisovalvo, B. BavassanoAbstract:Solar wind plasma is known to cool down more slowly while it is blown away from the Sun than expected from an adiabatic spherical expansion. Some source of heating is thus needed to explain the observed temperature radial profile. The presence of a nonlinear turbulent magnetohydrodynamic Energy Cascade has been recently observed in solar wind plasma. This provides for the first time a direct estimation of the turbulent Energy transfer rate, which can contribute to the in situ heating of the wind. The value of such contribution is shown to represent an important fraction (from 5% to 100%) of the total heating, and is strongly correlated with the wind temperature.
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observation of inertial Energy Cascade in interplanetary space plasma
Physical Review Letters, 2007Co-Authors: L Sorrisovalvo, Raffaele Marino, Vincenzo Carbone, Alain Noullez, Roberto Bruno, B. Bavassano, F Lepreti, P Veltri, E PietropaoloAbstract:: Direct evidence for the presence of an inertial Energy Cascade, the most characteristic signature of hydromagnetic turbulence (MHD), is observed in the solar wind by the Ulysses spacecraft. After a brief rederivation of the equivalent of Yaglom's law for MHD turbulence, a linear relation is indeed observed for the scaling of mixed third-order structure functions involving Elsasser variables. This experimental result firmly establishes the turbulent character of low-frequency velocity and magnetic field fluctuations in the solar wind plasma.
L Sorrisovalvo - One of the best experts on this subject based on the ideXlab platform.
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heating the solar wind by a magnetohydrodynamic turbulent Energy Cascade
The Astrophysical Journal, 2008Co-Authors: Raffaele Marino, Vincenzo Carbone, Alain Noullez, Roberto Bruno, L Sorrisovalvo, B. BavassanoAbstract:Solar wind plasma is known to cool down more slowly while it is blown away from the Sun than expected from an adiabatic spherical expansion. Some source of heating is thus needed to explain the observed temperature radial profile. The presence of a nonlinear turbulent magnetohydrodynamic Energy Cascade has been recently observed in solar wind plasma. This provides for the first time a direct estimation of the turbulent Energy transfer rate, which can contribute to the in situ heating of the wind. The value of such contribution is shown to represent an important fraction (from 5% to 100%) of the total heating, and is strongly correlated with the wind temperature.
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small scale Energy Cascade of the solar wind turbulence
The Astrophysical Journal, 2008Co-Authors: Olga Alexandrova, Vincenzo Carbone, P Veltri, L SorrisovalvoAbstract:Magnetic fluctuations in the solar wind are distributed according to Kolmogorov’s power law f −5/3 below the ion cyclotron frequency fci. Above this frequency, the observed steeper power law is usually interpreted in two different ways: a dissipative range of the solar wind turbulence or another turbulent Cascade, the nature of which is still an open question. Using the Cluster magnetic data we show that after the spectral break the intermittency increases toward higher frequencies, indicating the presence of non-linear interactions inherent to a new inertial range and not to the dissipative range. At the same time the level of compressible fluctuations raises. We show that the Energy transfer rate and intermittency are sensitive to the level of compressibility of the magnetic fluctuations within the small scale inertial range. We conjecture that the time needed to establish this inertial range is shorter than the eddy-turnover time, and is related to dispersive effects. A simple phenomenological model, based on the compressible Hall MHD, predicts the magnetic spectrum ∼ k −7/3+2α , which
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observation of inertial Energy Cascade in interplanetary space plasma
Physical Review Letters, 2007Co-Authors: L Sorrisovalvo, Raffaele Marino, Vincenzo Carbone, Alain Noullez, Roberto Bruno, B. Bavassano, F Lepreti, P Veltri, E PietropaoloAbstract:: Direct evidence for the presence of an inertial Energy Cascade, the most characteristic signature of hydromagnetic turbulence (MHD), is observed in the solar wind by the Ulysses spacecraft. After a brief rederivation of the equivalent of Yaglom's law for MHD turbulence, a linear relation is indeed observed for the scaling of mixed third-order structure functions involving Elsasser variables. This experimental result firmly establishes the turbulent character of low-frequency velocity and magnetic field fluctuations in the solar wind plasma.
Sébastien Galtier - One of the best experts on this subject based on the ideXlab platform.
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Energy Cascade rate in isothermal compressible magnetohydrodynamic turbulence
Journal of Plasma Physics, 2018Co-Authors: Nahuel Andrés, Fouad Sahraoui, Sébastien Galtier, Lina Hadid, Pablo Dmitruk, Pablo D. MininniAbstract:Three-dimensional direct numerical simulations are used to study the Energy Cascade rate in isothermal compressible magnetohydrodynamic turbulence. Our analysis is guided by a two-point exact law d ...
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compressible magnetohydrodynamic turbulence in the earth s magnetosheath estimation of the Energy Cascade rate using in situ spacecraft data
Physical Review Letters, 2018Co-Authors: Lina Hadid, Fouad Sahraoui, Sébastien Galtier, Shiyong HuangAbstract:: The first estimation of the Energy Cascade rate |e_{C}| of magnetosheath turbulence is obtained using the Cluster and THEMIS spacecraft data and an exact law of compressible isothermal magnetohydrodynamics turbulence. The mean value of |e_{C}| is found to be close to 10^{-13} J m^{-3} s^{-1}, at least 2 orders of magnitude larger than its value in the solar wind (∼10^{-16} J m^{-3} s^{-1} in the fast wind). Two types of turbulence are evidenced and shown to be dominated either by incompressible Alfvenic or compressible magnetosoniclike fluctuations. Density fluctuations are shown to amplify the Cascade rate and its spatial anisotropy in comparison with incompressible Alfvenic turbulence. Furthermore, for compressible magnetosonic fluctuations, large Cascade rates are found to lie mostly near the linear kinetic instability of the mirror mode. New empirical power-laws relating |e_{C}| to the turbulent Mach number and to the internal Energy are evidenced. These new findings have potential applications in distant astrophysical plasmas that are not accessible to in situ measurements.
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Energy Cascade rate in compressible fast and slow solar wind turbulence
The Astrophysical Journal, 2017Co-Authors: Lina Hadid, Fouad Sahraoui, Sébastien GaltierAbstract:Estimation of the Energy Cascade rate in the inertial range of solar wind turbulence has been done so far mostly within the incompressible magnetohydrodynamics (MHD) theory. Here, we go beyond that approximation to include plasma compressibility using a reduced form of a recently derived exact law for compressible, isothermal MHD turbulence. Using in-situ data from the THEMIS/ARTEMIS spacecraft in the fast and slow solar wind, we investigate in detail the role of the compressible fluctuations in modifying the Energy Cascade rate with respect to the prediction of the incompressible MHD model. In particular, we found that the Energy Cascade rate: i) is amplified particularly in the slow solar wind; ii) exhibits weaker fluctuations in spatial scales, which leads to a broader inertial range than the previous reported ones; iii) has a power law scaling with the turbulent Mach number; iv) has a lower level of spatial anisotropy. Other features of solar wind turbulence are discussed along with their comparison with previous studies that used incompressible or heuristic (non exact) compressible MHD models.
Vincenzo Carbone - One of the best experts on this subject based on the ideXlab platform.
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On the turbulent Energy Cascade in anisotropic magnetohydrodynamic turbulence
arXiv: Fluid Dynamics, 2010Co-Authors: Vincenzo Carbone, Luca Sorriso-valvo, Raffaele MarinoAbstract:The problem of the occurrence of an Energy Cascade for Alfv\'enic turbulence in solar wind plasmas was hystorically addressed by using phenomenological arguments based to the weakness of nonlinear interactions and the anisotropy of the Cascade in wave vectors space. Here, this paradox is reviewed through the formal derivation of a Yaglom relation from anisotropic Magnetohydrodynamic equation. The Yaglom relation involves a third-order moment calculated from velocity and magnetic fields and involving both Els\"asser vector fields, and is particularly useful to be used as far as spacecraft observations of turbulence are concerned.
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On the turbulent Energy Cascade in anisotropic magnetohydrodynamic turbulence
EPL, 2009Co-Authors: Vincenzo Carbone, Luca Sorriso-valvo, Raffaele MarinoAbstract:The problem of the occurrence of an Energy Cascade for Alfvenic turbulence in solar wind plasmas was historically addressed by using phenomenological arguments based to the sweeping of Alfvenic fluctuations by the large-scale magnetic field and the anisotropy of the Cascade in wave vectors space. Here, this paradox is reviewed through the formal derivation of a Yaglom relation from the anisotropic magnetohydrodynamic equation. The Yaglom relation involves a third-order moment calculated from velocity and magnetic fields and involving both Elsasser vector fields, and is particularly useful to be used as far as spacecraft obervations of turbulence are concerned.
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The Energy Cascade in Solar Wind MHD Turbulence
Earth Moon and Planets, 2009Co-Authors: Raffaele Marino, Luca Sorriso-valvo, Vincenzo Carbone, Alain Noullez, Roberto Bruno, B. BavassanoAbstract:Direct evidence for the presence of an inertial Energy Cascade, the most characteristic signature of hydromagnetic turbulence (MHD), is observed in the solar wind by the Ulysses spacecraft. A linear relation is indeed observed for the scaling of mixed third order structure functions involving Elsasser variables. This experimental result, confirming the prescription stemming from a theorem for MHD turbulence, firmly establishes the turbulent character of low-frequency velocity and magnetic field fluctuations in the solar wind plasma.
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heating the solar wind by a magnetohydrodynamic turbulent Energy Cascade
The Astrophysical Journal, 2008Co-Authors: Raffaele Marino, Vincenzo Carbone, Alain Noullez, Roberto Bruno, L Sorrisovalvo, B. BavassanoAbstract:Solar wind plasma is known to cool down more slowly while it is blown away from the Sun than expected from an adiabatic spherical expansion. Some source of heating is thus needed to explain the observed temperature radial profile. The presence of a nonlinear turbulent magnetohydrodynamic Energy Cascade has been recently observed in solar wind plasma. This provides for the first time a direct estimation of the turbulent Energy transfer rate, which can contribute to the in situ heating of the wind. The value of such contribution is shown to represent an important fraction (from 5% to 100%) of the total heating, and is strongly correlated with the wind temperature.
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small scale Energy Cascade of the solar wind turbulence
The Astrophysical Journal, 2008Co-Authors: Olga Alexandrova, Vincenzo Carbone, P Veltri, L SorrisovalvoAbstract:Magnetic fluctuations in the solar wind are distributed according to Kolmogorov’s power law f −5/3 below the ion cyclotron frequency fci. Above this frequency, the observed steeper power law is usually interpreted in two different ways: a dissipative range of the solar wind turbulence or another turbulent Cascade, the nature of which is still an open question. Using the Cluster magnetic data we show that after the spectral break the intermittency increases toward higher frequencies, indicating the presence of non-linear interactions inherent to a new inertial range and not to the dissipative range. At the same time the level of compressible fluctuations raises. We show that the Energy transfer rate and intermittency are sensitive to the level of compressibility of the magnetic fluctuations within the small scale inertial range. We conjecture that the time needed to establish this inertial range is shorter than the eddy-turnover time, and is related to dispersive effects. A simple phenomenological model, based on the compressible Hall MHD, predicts the magnetic spectrum ∼ k −7/3+2α , which
Alain Noullez - One of the best experts on this subject based on the ideXlab platform.
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The Energy Cascade in Solar Wind MHD Turbulence
Earth Moon and Planets, 2009Co-Authors: Raffaele Marino, Luca Sorriso-valvo, Vincenzo Carbone, Alain Noullez, Roberto Bruno, B. BavassanoAbstract:Direct evidence for the presence of an inertial Energy Cascade, the most characteristic signature of hydromagnetic turbulence (MHD), is observed in the solar wind by the Ulysses spacecraft. A linear relation is indeed observed for the scaling of mixed third order structure functions involving Elsasser variables. This experimental result, confirming the prescription stemming from a theorem for MHD turbulence, firmly establishes the turbulent character of low-frequency velocity and magnetic field fluctuations in the solar wind plasma.
-
heating the solar wind by a magnetohydrodynamic turbulent Energy Cascade
The Astrophysical Journal, 2008Co-Authors: Raffaele Marino, Vincenzo Carbone, Alain Noullez, Roberto Bruno, L Sorrisovalvo, B. BavassanoAbstract:Solar wind plasma is known to cool down more slowly while it is blown away from the Sun than expected from an adiabatic spherical expansion. Some source of heating is thus needed to explain the observed temperature radial profile. The presence of a nonlinear turbulent magnetohydrodynamic Energy Cascade has been recently observed in solar wind plasma. This provides for the first time a direct estimation of the turbulent Energy transfer rate, which can contribute to the in situ heating of the wind. The value of such contribution is shown to represent an important fraction (from 5% to 100%) of the total heating, and is strongly correlated with the wind temperature.
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observation of inertial Energy Cascade in interplanetary space plasma
Physical Review Letters, 2007Co-Authors: L Sorrisovalvo, Raffaele Marino, Vincenzo Carbone, Alain Noullez, Roberto Bruno, B. Bavassano, F Lepreti, P Veltri, E PietropaoloAbstract:: Direct evidence for the presence of an inertial Energy Cascade, the most characteristic signature of hydromagnetic turbulence (MHD), is observed in the solar wind by the Ulysses spacecraft. After a brief rederivation of the equivalent of Yaglom's law for MHD turbulence, a linear relation is indeed observed for the scaling of mixed third-order structure functions involving Elsasser variables. This experimental result firmly establishes the turbulent character of low-frequency velocity and magnetic field fluctuations in the solar wind plasma.