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Matthaeus WH, Wan M, Servidio S, Greco A, Osman KT, Oughton S, Dmitruk P. Intermittency, nonlinear dynamics and dissipation in the solar wind and astrophysical plasmas. Philos Trans A Math Phys Eng Sci 2015; 373:20140154. [PMID: 25848085 PMCID: PMC4394684 DOI: 10.1098/rsta.2014.0154] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/12/2015] [Indexed: 05/29/2023]
Abstract
An overview is given of important properties of spatial and temporal intermittency, including evidence of its appearance in fluids, magnetofluids and plasmas, and its implications for understanding of heliospheric plasmas. Spatial intermittency is generally associated with formation of sharp gradients and coherent structures. The basic physics of structure generation is ideal, but when dissipation is present it is usually concentrated in regions of strong gradients. This essential feature of spatial intermittency in fluids has been shown recently to carry over to the realm of kinetic plasma, where the dissipation function is not known from first principles. Spatial structures produced in intermittent plasma influence dissipation, heating, and transport and acceleration of charged particles. Temporal intermittency can give rise to very long time correlations or a delayed approach to steady-state conditions, and has been associated with inverse cascade or quasi-inverse cascade systems, with possible implications for heliospheric prediction.
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Affiliation(s)
- W H Matthaeus
- Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA Dipartimento di Fisica, Università della Calabria, Arcavacata, Rende, Italy Dipartimento di Fisica e Astronomia, Università di Firenze, Firenze, Italy
| | - Minping Wan
- Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA
| | - S Servidio
- Dipartimento di Fisica, Università della Calabria, Arcavacata, Rende, Italy
| | - A Greco
- Dipartimento di Fisica, Università della Calabria, Arcavacata, Rende, Italy
| | - K T Osman
- Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL, UK
| | - S Oughton
- Department of Mathematics, University of Waikato, Hamilton, New Zealand
| | - P Dmitruk
- Departamento de Fisica, FCEN, Universidad de Buenos Aires, Buenos Aires, Argentina
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Oughton S, Matthaeus WH, Wan M, Osman KT. Anisotropy in solar wind plasma turbulence. Philos Trans A Math Phys Eng Sci 2015; 373:20140152. [PMID: 25848082 PMCID: PMC4394683 DOI: 10.1098/rsta.2014.0152] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/04/2015] [Indexed: 06/01/2023]
Abstract
A review of spectral anisotropy and variance anisotropy for solar wind fluctuations is given, with the discussion covering inertial range and dissipation range scales. For the inertial range, theory, simulations and observations are more or less in accord, in that fluctuation energy is found to be primarily in modes with quasi-perpendicular wavevectors (relative to a suitably defined mean magnetic field), and also that most of the fluctuation energy is in the vector components transverse to the mean field. Energy transfer in the parallel direction and the energy levels in the parallel components are both relatively weak. In the dissipation range, observations indicate that variance anisotropy tends to decrease towards isotropic levels as the electron gyroradius is approached; spectral anisotropy results are mixed. Evidence for and against wave interpretations and turbulence interpretations of these features will be discussed. We also present new simulation results concerning evolution of variance anisotropy for different classes of initial conditions, each with typical background solar wind parameters.
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Affiliation(s)
- S Oughton
- Department of Mathematics, University of Waikato, Hamilton 3240, New Zealand
| | - W H Matthaeus
- Department of Physics and Astronomy, University of Delaware, DE 19716, USA
| | - M Wan
- Department of Physics and Astronomy, University of Delaware, DE 19716, USA
| | - K T Osman
- Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL, UK
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Osman KT, Matthaeus WH, Kiyani KH, Hnat B, Chapman SC. Proton kinetic effects and turbulent energy cascade rate in the solar wind. Phys Rev Lett 2013; 111:201101. [PMID: 24289672 DOI: 10.1103/physrevlett.111.201101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2013] [Indexed: 06/02/2023]
Abstract
The first observed connection between kinetic instabilities driven by proton temperature anisotropy and estimated energy cascade rates in the turbulent solar wind is reported using measurements from the Wind spacecraft at 1 AU. We find enhanced cascade rates are concentrated along the boundaries of the (β∥, T⊥/T∥) plane, which includes regions theoretically unstable to the mirror and firehose instabilities. A strong correlation is observed between the estimated cascade rate and kinetic effects such as temperature anisotropy and plasma heating, resulting in protons 5-6 times hotter and 70%-90% more anisotropic than under typical isotropic plasma conditions. These results offer new insights into kinetic processes in a turbulent regime.
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Affiliation(s)
- K T Osman
- Centre for Fusion, Space, and Astrophysics, University of Warwick, Coventry CV4 7AL, United Kingdom
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Osman KT, Matthaeus WH, Hnat B, Chapman SC. Kinetic signatures and intermittent turbulence in the solar wind plasma. Phys Rev Lett 2012; 108:261103. [PMID: 23004954 DOI: 10.1103/physrevlett.108.261103] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Indexed: 06/01/2023]
Abstract
A connection between kinetic processes and intermittent turbulence is observed in the solar wind plasma using measurements from the Wind spacecraft at 1 A.U. In particular, kinetic effects such as temperature anisotropy and plasma heating are concentrated near coherent structures, such as current sheets, which are nonuniformly distributed in space. Furthermore, these coherent structures are preferentially found in plasma unstable to the mirror and firehose instabilities. The inhomogeneous heating in these regions, which is present in both the magnetic field parallel and perpendicular temperature components, results in protons at least 3-4 times hotter than under typical stable plasma conditions. These results offer a new understanding of kinetic processes in a turbulent regime, where linear Vlasov theory is not sufficient to explain the inhomogeneous plasma dynamics operating near non-Gaussian structures.
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Affiliation(s)
- K T Osman
- Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry, CV4 7AL, United Kingdom.
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Abstract
Evidence for nonuniform heating in the solar wind plasma near current sheets dynamically generated by magnetohydrodynamic (MHD) turbulence is obtained using measurements from the ACE spacecraft. These coherent structures only constitute 19% of the data, but contribute 50% of the total plasma internal energy. Intermittent heating manifests as elevations in proton temperature near current sheets, resulting in regional heating and temperature enhancements extending over several hours. The number density of non-Gaussian structures is found to be proportional to the mean proton temperature and solar wind speed. These results suggest magnetofluid turbulence drives intermittent dissipation through a hierarchy of coherent structures, which collectively could be a significant source of coronal and solar wind heating.
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Affiliation(s)
- K T Osman
- Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry, CV4 7AL, United Kingdom.
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Osman KT, Wan M, Matthaeus WH, Weygand JM, Dasso S. Anisotropic third-moment estimates of the energy cascade in solar wind turbulence using multispacecraft data. Phys Rev Lett 2011; 107:165001. [PMID: 22107393 DOI: 10.1103/physrevlett.107.165001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Indexed: 05/31/2023]
Abstract
The first direct determination of the inertial range energy cascade rate, using an anisotropic form of Yaglom's law for magnetohydrodynamic turbulence, is obtained in the solar wind with multispacecraft measurements. The two-point mixed third-order structure functions of Elsässer fluctuations are integrated over a sphere in magnetic field-aligned coordinates, and the result is consistent with a linear scaling. Therefore, volume integrated heating and cascade rates are obtained that, unlike previous studies, make only limited assumptions about the underlying spectral geometry of solar wind turbulence. These results confirm the turbulent nature of magnetic and velocity field fluctuations in the low frequency limit, and could supply the energy necessary to account for the nonadiabatic heating of the solar wind.
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Affiliation(s)
- K T Osman
- Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Delaware 19716, USA.
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Servidio S, Greco A, Matthaeus WH, Osman KT, Dmitruk P. Statistical association of discontinuities and reconnection in magnetohydrodynamic turbulence. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2011ja016569] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- S. Servidio
- Dipartimento di Fisica; Università della Calabria; Cosenza Italy
| | - A. Greco
- Dipartimento di Fisica; Università della Calabria; Cosenza Italy
| | - W. H. Matthaeus
- Bartol Research Institute, Department of Physics and Astronomy; University of Delaware; Newark Delaware USA
| | - K. T. Osman
- Bartol Research Institute, Department of Physics and Astronomy; University of Delaware; Newark Delaware USA
| | - P. Dmitruk
- Departamento de Física, Facultad de Ciencias Exactas y Naturales; Universidad de Buenos Aires; Buenos Aires Argentina
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Abstract
Systematics are proposed for the (n, p), (n, alpha) and (n, 2n) reactions cross-sections at 14.5 MeV neutron energy based on the statistical model, with consideration of the Q-value dependence and odd-even effects. The obtained relations are compared with other recently proposed systematics based on the statistical model as well as on the asymmetry parameter dependence.
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Affiliation(s)
- F I Habbani
- Department of Physics, Faculty of Science, University of Khartoum, Sudan.
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