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@PHDTHESIS{Jacobs:988659,
      author       = {Jacobs, Hanno},
      othercontributors = {Mertsch, Philipp and Wiebusch, Christopher},
      title        = {{S}uppressed diffusion around cosmic ray sources and impact
                      on galactic propagation},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {RWTH Aachen University},
      reportid     = {RWTH-2024-06343},
      pages        = {1 Online-Ressource : Illustrationen},
      year         = {2024},
      note         = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
                      University; Dissertation, RWTH Aachen University, 2024},
      abstract     = {At the beginning of the 20th century a variety of
                      observations found that the Earth is constantly bombarded by
                      charged high energy particles from space. These cosmic rays
                      mainly consist of protons, but also contain heavier
                      elements. Over a large range in energy from MeV to EeV they
                      resemble a power law. At GeV energies their arrival
                      directions are nearly isotropic, since charged particles get
                      deflected in the turbulent magnetic fields in the Galaxy.
                      This prevents a direct tracking of the particles back to
                      their sources. From the ratios of hadronic cosmic rays it is
                      possible to deduce that particles must propagate diffusively
                      throughout the Galaxy. Thereby, the parameters of models we
                      fit to these data are galactic averages. In contrast, high
                      energy $\gamma$-rays are produced by cosmic rays and
                      directly point back to their origin. With this it is
                      possible to indirectly probe the distribution of comic rays
                      within the Galaxy. Recent observations of $\gamma$-rays
                      around pulsars and supernova remnants, both potential
                      sources, indicate that diffusion in these regions is more
                      than two orders of magnitude lower than in the galactic
                      average. This indicates that the conditions within the
                      Galaxy are far from homogeneous. In this thesis, we
                      investigate whether cosmic rays themselves can produce the
                      suppressed diffusion. The basic idea is that in the vicinity
                      of the source the strong spatial gradient of the cosmic ray
                      density gives rise to the resonant streaming-instability.
                      This produces magnetic waves upon which they scatter, a
                      process called self-confinement. We make use of
                      finite-difference codes to investigate the surroundings of
                      supernova remnants. We extend existing models below
                      $10\,\mathrm{GeV}$ and show that suppressed diffusion can
                      exist for up to $1\,\mathrm{Myr}$ after the supernova. The
                      same mechanism was proposed to explain
                      TeV-$\gamma$-ray-halos around pulsars. We implement the
                      cascade of turbulence in existing models and show that the
                      effectivity of the streaming-instability crucially depends
                      on the large scale magnetic field. Our calculations
                      indicate, that the streaming instability alone is not able
                      to explain the observations around the pulsar Geminga.
                      Additionally, we investigate the effects of suppressed
                      diffusion in the galactic disk on hadronic cosmic ray
                      ratios. The basic idea is that unstable particles are
                      confined within the disk for longer if the diffusion
                      coefficient is smaller. Then, the ratio of unstable to
                      stable nuclei is increased compared to standard predictions.
                      We develop a semi-analytical two-zone model of the Galaxy
                      with a reduced diffusion coefficient in the galactic disk
                      compared to the galactic halo and show that this model can
                      be constrained by recent AMS-02 $\mathrm{^{10}Be/^9Be}$
                      data. For the case that the diffusion coefficient in the
                      disk represents an average over zones of low and high
                      diffusion, we investigate the filling fraction of the
                      suppression zones with stochastic differential equations.
                      Finally, we highlight the impact of different spallation
                      cross-section parametrisations on our findings.},
      cin          = {136320 / 132730 / 130000},
      ddc          = {520},
      cid          = {$I:(DE-82)136320_20140620$ / $I:(DE-82)132730_20170609$ /
                      $I:(DE-82)130000_20140620$},
      pnm          = {DFG project 490751943 - Kosmische Strahlung im sehr lokalen
                      interstellaren Medium (490751943)},
      pid          = {G:(GEPRIS)490751943},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2024-06343},
      url          = {https://publications.rwth-aachen.de/record/988659},
}