Data-validated, Self-consistent Modelling of Turbulence and Particle Transport in the Heliosphere

• Applicants: Privatdozent Dr. Horst Fichtner; Professor Dr. Bernd Heber
• Subject Area: Astrophysics and Astronomy
• Term: from 2012 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 221245396

• Final Report Year: 2021

Final Report Abstract

The project had the overarching goal to address the central science question whether current combined state-of-the-art kinetic transport, magnetohydrodynamic, and turbulence evolution models can be used to explain time-dependent, three-dimensional, multi-point spacecraft data. With this research project we continued the successful collaboration between the research groups of the two applicants H. Fichtner (Ruhr-Universität Bochum) and B. Heber (Christian Albrechts-Universität zu Kiel) with M.S. Potgieter (North-West University, Campus Potchefstroom, South Africa, now retired) on the topic of ‘particle transport in heliospheric magnetic field structures’. The objectives of the project aimed at improving previous approaches by applying, for the first time, a model suite being self-consistent as far as possible. The novel aspects of the new approach are detailed comparisons with three-dimensional multi-point spacecraft data, realistic inner (solar) boundary conditions, and an explicit consideration of the slab and (quasi-)two-dimensional turbulent components of the heliospheric magnetic field. The project activities carried out comprised the following studies: (a) a coupling of a stochastic differential equation (SDE) code for the kinetic transport of energetic particles with the magnetohydrodynamical (MHD) code C RONOS for the dynamics of the solar wind and the turbulence within prepared the originally intended self-consistent simulations and their subsequent comparison to multi-point spacecraft observations (the latter applications could not be realized as a consequence of the significantly reduced funding compared to the support applied for); (b) the development of a new method to treat the time-dependent drifts of energetic particles in the heliospheric magnetic field for varying solar activity, which paves the way to derive the inner boundary conditions for both the SDE code and the MHD code from the same data, namely solar magnetograms, (c) a study of the effect of slab and (quasi-)two-dimensional turbulence on meandering field lines and in turn on solar energetic particle events, (d) the derivation of a new source spectrum of Jovian electrons, (e) the determination of transport parameters as well as of the residence times of these particles in the inner heliosphere, and (f) analyses of multi-point spacecraft data of Forbush decreases of Galactic cosmic rays due to coronal mass ejcections. The achieved results from both modelling and data analyses add considerably to a simultaneous treatment of thermal plasma and energetic particles. Based on (a) and (b) it is now possible to significantly improve corresponding self-consistent kinetic transport and MHD modeling of energetic particles within a dynamic solar wind. With (c) a contribution to the longitudinal spread of solar energetic particle events has been made. The study of Jovian electrons (d) and (e) established a new source spectrum and the residence as well as propagation times of these particles, respectively. Finally, with (f) the effect of prominent heliospheric magnetic structures, namely coronal mass ejection, on the transport of Galactic cosmic rays was studied. The work was carried out, as planned, via the collaboration of the two research groups at the Ruhr-Universität Bochum and the Christian-Albrechts-Universität zu Kiel and their cooperation with scientists from the North-West University, Campus Potchefstroom in South Africa. Despite the considerably reduced budget, and despite the additional difficulties imposed by the Covid-19 pandemic (that impacted both the work by the individual institutions and the collaboration activities) a majority of the project objectives could be reached and, thus, worthwile contributions to contemporary research have been made.

Publications

• Jovian electrons in the inner heliosphere. Proposing a new source spectrum based on 30 years of measurements, Astronomy & Astrophysics, 13, id.A28, 2018
  Vogt, A., Heber, B., Kopp, A., Potgieter, M.S., Strauss, R.D.
  
• The residence-time of Jovian electrons in the inner heliosphere, Astronomy & Astrophysics, 642, id.A170, 2020
  Vogt, A., Engelbrecht, N.E., Strauss, R.D., Heber, B., Kopp, A., Herbst, K.
  
• Cosmic-Ray Transport in Heliospheric Magnetic Structures. III. Implications of Solar Magnetograms for the Drifts of Cosmic Rays The Astrophysical Journal, 2021
  Kopp, A., Raath, J.L., Fichtner, H., Potgieter, M.S., Ferreira, S.E.S., Heber, B.
  
• Determining Charged Particle Residence Times: An SDE-based Modelling Approach, Ph.D. thesis (Supervisor B. Heber), Christian-Albrechts-Universität zu Kiel, 2021
  Vogt, A.
  
• Implications of Solar Magnetograms for the Drifts of Cosmic Rays, Proceedings of Science, 395, 1342, 2021
  Fichtner, H., Kopp, A.
  
• The effect and properties of drifts in the heliosphere Astronomy & Astrophysics, 2021
  Raath, J.L., Ferreira, S.E.S., Kopp, A.
  
• Analytic modelling of recurrent Forbush decreases caused by corotating interaction regions, Astronomy & Astrophysics, 2022
  Vršnak, B., Dumbović , M. Heber, B., Kirin, A.
  
• Numerical and experimental evidence for a new interpretation of residence times in space, Astronomy & Astrophysics, 2022
  Vogt, A., Engelbrecht, N.E., Heber, B., Kopp, A., Herbst, K.