Turbulenztransport in sub-Alfvenischen und subsonischen astrophysikalischen Plasmaflüssen
Zusammenfassung der Projektergebnisse
The main goals of the research project were a quantitative assessment of the transport of turbulence in the sub-Alfvénic and subsonic regimes of astrophysical plasma flows, particularly of the solar wind in the so-called inner heliosheath, i.e. the region between the solar wind termination shock and the heliopause, and a quantitative study of the related transport of energetic particles. Three scientific key questions were identified: (1) How can the transport of turbulence in the partially sub-Alfvénic and subsonic inner heliosheath and in stellar astrosheaths be described quantitatively within the framework of a multi-component model? (2) How does the turbulence evolution in the inner heliosheath and in stellar astrosheaths influence the spatial and temporal variation of the transport parameters of cosmic rays? (3) What are the solutions of the cosmic ray transport equation when using the new compressible turbulence model to obtain the transport parameters? The objectives of the project aimed at improving previous approaches by supplementing the much needed models of turbulence evolution with a new description that allows for a simultaneous and self-consistent treatment of quasi-2D, wave-like, and compressive fluctuations and, thereby, establishes a significantly improved framework for the modelling of the transport conditions of energetic particles in both the inner heliosheath and in stellar astrosheaths. With this research project we continued the previous collaboration between the Ruhr-Universität Bochum and the University of Waikato, New Zealand that was started with a bi-lateral 1-year ainitiation project. Based on the results of this project we extended the modelling of the transport of turbulence into the region beyond the solar wind termination shock. This modelling was made possible by combining the complementary expertise of the two groups in the field of magnetohydrodynamic (MHD) turbulence (primarily Waikato) and helio- and astrospheric MHD modelling (primarily Bochum). The project activities carried out comprised the following studies: (a) the computation of compressible (mirror-mode) fluctuations in a self-consistently computed, three-dimensional, (due to the interstellar magnetic field) asymmetric heliosphere with a turbulent solar wind plasma, which represents the first model for compressible turbulence in the entire inner heliosheath; (b) the development of a time-dependent, three-dimensional magnetohydrodynamic ‘six-equation’ model for the transport of turbulence that (i) is self-consistently evolving in a dynamic heliosphere, (ii) allowed the so-called energy difference to vary with location and (iii) associates different characteristic length scales to each of the the Elsasser energies and the energy difference; (c) the first derivation of an analytical representation for the time-dependent magnetic field in the inner heliosheath, and (d) contributions to recent activities regarding the structure of astrospheres, astrosheaths, and the transport of cosmic rays within.
Projektbezogene Publikationen (Auswahl)
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On the Generation of Compressible Mirror-mode Fluctuations in the Inner Heliosheath. The Astrophysical Journal, 901(1), 76.
Fichtner, Horst; Kleimann, Jens; Yoon, Peter H.; Scherer, Klaus; Oughton, Sean & Engelbrecht, N. Eugene
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An exact, time-dependent analytical solution for the magnetic field in the inner heliosheath. Journal of Physics A: Mathematical and Theoretical, 55(49), 495702.
Röken, Christian; Kleimann, Jens & Fichtner, Horst
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The Structure of the Large-Scale Heliosphere as Seen by Current Models. Space Science Reviews, 218(4).
Kleimann, Jens; Dialynas, Konstantinos; Fraternale, Federico; Galli, André; Heerikhuisen, Jacob; Izmodenov, Vladislav; Kornbleuth, Marc; Opher, Merav & Pogorelov, Nikolai
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Turbulence in the Outer Heliosphere. Space Science Reviews, 218(6).
Fraternale, Federico; Adhikari, Laxman; Fichtner, Horst; Kim, Tae K.; Kleimann, Jens; Oughton, Sean; Pogorelov, Nikolai V.; Roytershteyn, Vadim; Smith, Charles W.; Usmanov, Arcadi V.; Zank, Gary P. & Zhao, Lingling
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A Three-dimensional Model for the Evolution of Magnetohydrodynamic Turbulence in the Outer Heliosphere. The Astrophysical Journal, 953(2), 133.
Kleimann, Jens; Oughton, Sean; Fichtner, Horst & Scherer, Klaus
