Transport of suprathermal and energetic ions in the heliosphere and their injection and acceleration at shocks driven by coronal mass ejections
Zusammenfassung der Projektergebnisse
There are two fundamental types of fluid turbulence: Hydrodynamic i.e. Kolmogorov-type turbulence and magnetohydrodynamic i.e. Iroshnikov-Kraichnan-type turbulence. Kolmogorov developed his scaling law for the power spectral density as a function of wave number k = 2π/λ on minimum assumptions: Some source feeds energy from large spatial scales (e.g. the size of a locomotive in a wind tunnel) into all smaller scales of size λ. At scale size λ the typical amplitude of the turbulence is dv. Kolmogorov used the argument of self-similarity of all scale sizes: Pictures of the turbulent flow always look similar no matter how much we zoom in, as long as the scale size is in the inertial range i.e. larger than the small dissipation scale, where the energy of the turbulent motions is dissipated into heat of the fluid. From this argument, it follows that the turbulent speed amplitude dv(λ) at scale size λ scales as a power law with this scale size λ. In this work, first direct observational evidence has been found that one needs to include the Alfven time τA as additional characteristic scale size into the derivation of the self-sinularity law for turbulence in a magnetized plasma as has been postulated by Iroshnikov and Kraichnan. The Alfven time τA = k/vA is the characteristic time scale of the most fundamental wave in a magnetized plasma, the Alfven wave, where vA is the Alfven speed. This Alfven time determines the cascading time scale of magnetohydrodynamic turbulence. The second important finding of this work is that the turbulent speed fluctuations in the solar wind are more important for ion acceleration processes, at least for the Anomalous Cosmic Rays, than the speed jump at shocks in the solar wind e.g. the solar wind termination shock. Two fundamental acceleration processes of ions in the solar wind are denoted by first-order Fermi acceleration and by stochastic acceleration. In the first process, energy is transferred to ions due to ping-pong bouncing of ions between the upstream and the downstream plasma having a speed difference ∆V. In the second process, ions bounce between turbulently distributed speed differences in the solar wind flow. Ultimately, the second, stochastic process transfers more energy to suprathermal ions than the first process, which is localized to regions near a shock wave. This view is promoted by Fisk and Gloeckler (2008). The third important finding is that a plasma instability has been identified that initiates the transition of a quasi-parallel shock. These are the proton cyclotron waves driven by slightly suprathermal protons. At present, it is also studied how the same type of wave in the electron branch (whistler waves) initiate the narrow transition of a quasi-perpendicular plasma shock. The latter is studied in CLUSTER data. The determination of the cascading time scale in the solar wind can be considered as a surprise. It was originally not planned to find this result. The proposal has been written along standard lines, but some ideas come as a surprise. All three major findings could be published in the media. Plasma physics may get attention in the media for two reasons: 1) One of the future energy sources may be controlled plasma fusion, and 2) plasma physics are important in Astrophysics. 99% of visible matter consist of plasma.
Projektbezogene Publikationen (Auswahl)
-
Isotopic Composition of the Solar Wind Inferred from In-Situ Spacecraft, Symposium on the Composition of Matter honoring Johannes Geiss on the occasion of his 80th birthday, September 11-15, Grindelwald, Switzerland, 2006
R. Kallenbach, K. Bamert, and M. Hilchenbach
-
Stream-limited transport of Solar Energetic Particles, 36th COSPAR Scientific Assembly, July 16-23, Beijing, China, 2006
X. Wang, K. Bamert, P. Bochlser, M. Hilchenbach, F. Ipavich, B. Klecke, P. Wurz, and the CELIAS Team
-
Determination of the eddy turn-over time in the solar wind from turbulent wave spectra upstream of interplanetary shocks driven by coronal mass ejections, SOHO/CELI AS-STEREO/PLASTIC-SEPT Workshop, March 13-16, Kiel, Germany, 2007
K. Bamert, R. Kallenbach, M. Hilchenbach, C.W. Smith, and P. Wurz
-
Determination of the eddy turn-over time in the solar wind, 6th Annual International Astrophysics Conference on "Turbulence and Nonlinear Processes in Astrophysical Plasmas", March 16-22, Honolulu, Hawaii, USA, 2007
K. Bamert, R. Kallenbach, M. Hilchenbach, and C.W. Smith
-
Determination of the eddy turn-over time in the solar wind, in: Turbulence and Nonlinear Processes in Astrophysical Plasmas; 6th Annual International Astrophysics Conference. AIP Conference Proceedings, Vol. 932, pp. 69-74, 2007
K. Bamert, E. Kallenbach, M. Hilchenbach, and C.W. Smith
-
Direct evidence for stochastic acceleration in interplanetary space, SHINE Workshop, July 30-August 3, Whistler, BC, Canada, 2007
K. Bamert and R. Kallenbach
-
Isotopic Composition of the Solar Wind Inferred from In-Situ Spacecraft Measurements, Space Sci. Rev., Volume 130, Issue 1-4, pp. 173-182, 2007
R. Kallenbach, K. Bamert, and M. Hilchenbach
-
Isotopic Composition of the Solar Wind Inferred from In-Situ Spacecraft, The Composition of Matter: Symposium honouring Johannes Geiss on the occasion of his 80th birthday. By Rudolf von Steiger, George Gloeckler and Glenn M. Mason. Space Sci. Rev., Vol. 130, Issues 1-4, 2007
R. Kallenbach, K. Bamert, and M. Hilchenbach
-
Evidence for Iroshnikov-Kraichnan type turbulence in the solar wind upstream of interplanetary travelling shocks. Joint CELIAS/PLASTIC/SEPT Workshop, March 17-19, Ascona, Switzerland, 2008
K. Bamert, R. Kallenbach, J.A. le Roux, M. Hilchenbach, C. W. Smith, and P. Wurz
-
Evidence of Iroshnikov-Kraichnan-Type Turbulence in the Solar Wind Upstream of Interplanetary Traveling Shocks, Astrophys. J., Vol. 675, Issue 1, pp. L45-L48, 2008
K. Bamert, R. Kallenbach, J.A. Le Roux, M. Hilchenbach, C.W. Smizh, and P. Wurz
-
Acceleration of the Anomalous Component of Cosmic Rays Revisited, Verhandlungen der Deutschen Physikalischen Gesellschaft, Energetic Particle Acceleration in Space and Laboratory, SYPA 1.5, April 1, Zahnklinik Greifswald, Germany, 2009.
R. Kallenbach, K. Bamert, and M. Hilchenbach
-
Acceleration of the Anomalous Component of the Cosmic Rays Revisited, Astrophysics and Space Science Transactions (ASTRA), 2009
R. Kallenbach, K. Bamert, and M. Hilchenbach
