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@PHDTHESIS{Kuhlen:847322,
author = {Kuhlen, Marco},
othercontributors = {Mertsch, Philipp and Ahlers, Markus},
title = {{S}mall-scale anisotropies in cosmic ray arrival
directions},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {RWTH Aachen University},
reportid = {RWTH-2022-05246},
pages = {1 Online-Ressource : Illustrationen},
year = {2022},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, RWTH Aachen University, 2022},
abstract = {The arrival directions of TeV-PeV cosmic rays are
remarkably isotropic. This is understood to be the result of
charged particles performing a random walk through our
galaxy due to their scattering on the turbulent magnetic
field. While in this standard picture of cosmic ray
diffusion small anisotropies can exist, they are limited to
the largest angular scales. High-statistics observatories
like IceCube and HAWC however, have detected significant
deviations from isotropy down to angular scales as small as
$10^\circ$. Resolving this contradiction requires a better
understanding of the transport of charged cosmic rays in our
galaxy. In this thesis, we explain the formation of
anisotropies on small angular scales by considering the
correlated transport of pairs of cosmic rays through the
same realization of magnetic field turbulence. The creation
of small-scale anisotropies, we argue, is a reflection of
the unique manifestation of the turbulent magnetic field
experienced by cosmic rays on time scales in between the
early ballistic and late diffusive regimes of cosmic ray
transport. The angular power spectrum of cosmic rays can
thus be understood as the imprint of the local individual
magnetic field realization on the cosmic ray distribution.
We investigate this effect using two distinct approaches.
First, we run numerical test particle simulations,
propagating charged particles through synthetic magnetic
field turbulence. For the first time, we are able to show
the map of cosmic ray arrival directions at the TV
rigidities corresponding to the observations. To resolve the
large dynamical range of the turbulent magnetic field
required, we set up the magnetic field using nested grids
with different resolutions. Second, we compute the angular
power spectrum of cosmic ray arrival directions analytically
by using a perturbative diagrammatic approach. In this
formalism the correlations of the particle trajectories are
taken into account explicitly. We show that, for the
assumption of magneto-static slab-like magnetic field
turbulence, small-scale anisotropies from the correlated
transport of charged cosmic rays through turbulent magnetic
fields are expected and find excellent agreement with the
angular power spectra from the numerical test particle
simulations. Due to their unique sensitivity, measurements
of the anisotropies in the arrival directions of cosmic rays
will prove to be an invaluable tool to constrain the
properties of the turbulent magnetic field in our galactic
neighborhood.},
cin = {132730 / 130000},
ddc = {520},
cid = {$I:(DE-82)132730_20170609$ / $I:(DE-82)130000_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2022-05246},
url = {https://publications.rwth-aachen.de/record/847322},
}
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