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A calibration neutron monitor for long-term cosmic ray modulation studies / H. KrügerKrüger, Helena January 2006 (has links)
The propagation of high-energy cosmic rays is influenced by the time-varying heliospheric
magnetic field embedded in the solar wind, and by the geomagnetic field. To penetrate
through this geomagnetic field, they must have a rigidity that exceeds the geomagnetic cutoff
rigidity for a given position on the earth. In the atmosphere, the primary cosmic rays interact
with atmospheric nuclei, to form a cascade of secondary particles. Neutron monitors record
these secondary cosmic rays, mainly the neutrons, with energies about a decade higher than
detected by most spacecraft.
Since neutron monitors are integral detectors, each with its own detection efficiency, energy
spectra cannot readily be derived from their observations. One way to circumvent this is by
conducting latitudinal surveys with mobile neutron monitors. Another way is to use the
worldwide stationary neutron monitor network, but then the counting rates of these monitors
must be normalised sufficiently accurate against one another. For this reason two portable
calibration neutron monitors were built at the Potchefstroom campus of the North-West
University and completed in 2002.
To achieve sufficient calibration accuracy, several properties of the calibrator are
investigated in this work. Effects such as atmospheric pressure variations, diurnal variations,
short-term scintillations, and multiplicity, contribute to the fluctuations of the counting rate of a
neutron monitor. Due to these effects, the coefficient of variation of the calibrator is
determined to be -40% larger than the Poisson deviation. The energy response of the
calibrator over the cutoff rigidity interval from the poles to the equator is investigated, with the
result that it is almost 4% larger than that of a standard 3NM64 neutron monitor. It is also
determined that not only the calibrator, but also the stationary NM64 and IGY neutron
monitors, have fairly large instrumental temperature sensitivity, which must be accounted for
in calibration procedures. Furthermore, the calibrator has a large sensitivity to the type of
surface beneath it, influencing its counting rate by as much as 5%. This investigation is
incomplete and requires further experimentation before the calibration of the stationary
neutron monitors can start.
When calibrations of a significant number of the worldwide neutron monitors are done, their
intensity spectra as derived from differential response functions, will provide experimental
data for modulation studies at rigidities above 1 GV. / Thesis (Ph.D. (Physics))--North-West University, Potchefstroom Campus, 2006.
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An ab initio approach to the heliospheric modulation of galactic cosmic rays / Jaco MinnieMinnie, Jaco January 2006 (has links)
In the present study we aim to further our understanding of charged particle transport in a magnetized
medium. To this end, we perform direct numerical simulations of particle transport in
a turbulent magnetic field. From the particle trajectories we calculate diffusion and drift coefficients.
In contrast to previous numerical simulations of this nature, we also consider a background
magnetic field that contains a gradient perpendicular to the magnetic field direction. By
using a non-uniform background magnetic field, we can investigate the simultaneous large scale
drift due to the gradient in the background magnetic field and the diffusion due to the turbulence
which is superimposed on this background magnetic field. Upon comparison with the
simulated diffusion coefficients, the newly proposed weakly non-linear theory (WNLT) of Shalchi
et al. (2004b) seems to be the most appropriate theory for the simultaneous description of parallel and
perpendicular diffusion over a wide range of fluctuation amplitude and particle rigidity. As
for the effect of large scale drift on perpendicular diffusion, we find that under conditions of
small amplitude turbulence and/ or high particle rigidity the transport perpendicular to the background
field can exhibit super-diffusive behaviour. Diffusive behaviour seems to be recovered for
the cases when the turbulence amplitude is sufficiently large and/ or the particle rigidity is sufficiently
small. We furthermore find that both the drift coefficient and the drift speed are reduced
from their weak scattering counterparts in the presence of scattering, with the reduction becoming
more pronounced with increasing turbulence amplitude. For the drift coefficient in particular,
the reduction from its weak scattering counterpart behaves differently for the cases in which the
background magnetic field is either uniform or non-uniform. For the former case the reduction is
predominantly at small rigidities, while for the latter case the reduction is predominantly at large
rigidities. The latter result might be of significance for heliospheric modulation models in which
the background magnetic field is highly non-uniform. Finally, we use a two-dimensional steadystate
cosmic ray modulation model to see how our improved understanding of the underlying
transport processes influences the overall cosmic ray modulation in the heliosphere. We conclude
that in the absence of a theory which connects large scale drift with small scale diffusion, any
statements about the inadequacy of a two-dimensional steady-state modulation model might be
premature. / Thesis (Ph.D. (Physics))--North-West University, Potchefstroom Campus, 2006.
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A GPS-based method for pressure corrections to neutron monitor data / Izak G. MorkelMorkel, Izak Gerhardus January 2008 (has links)
Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2008.
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A GPS-based method for pressure corrections to neutron monitor data / Izak G. MorkelMorkel, Izak Gerhardus January 2008 (has links)
Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2008.
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Single grain detrital cosmogenic Ne-21 analysis a new tool to study long-term landscape evolution /Codilean, Alexandru Tiberiu. January 2008 (has links)
Thesis (Ph.D.) - University of Glasgow, 2008. / Ph.D. thesis submitted to the Department of Geographical and Earth Sciences, Faculty of Physical Sciences, University of Glasgow, 2008. Includes bibliographical references. Print version also available.
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Ionisatie door kosmische straling en gamma-stralingClay, Pieter Hajo. January 1942 (has links)
Academisch proefschrift--Amsterdam. / "Summary": p. 232-234. "Stellingen": [4] p. inserted. "Literatuurlijst": p. 235-240.
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A new measurement of the intensities of heavy cosmic-ray nuclei around 1 TeV/nucleon /Gahbauer, Florian Helmuth. January 2003 (has links)
Thesis (Ph. D.)--University of Chicago, Department of Physics, March 2003. / Includes bibliographical references. Also available on the Internet.
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Cosmogenic nuclides as a surface exposure dating tool: improved altitude/latitude scaling factors for production ratesDesilets, Darin Maurice. January 2005 (has links) (PDF)
Dissertation (PhD)--University of Arizona, Tucson, Arizona, 2005.
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Design, calibration, and early results of a surface array for detection of ultrahigh energy cosmic raysAllison, Patrick S., January 2007 (has links)
Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 307-319).
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Mesure et phénoménologie du rayonnement cosmique avec l'expérience CREAM / Cosmic rays measurements and phenomenology with CREAM and AMS experimentCoste, Benoît 03 October 2012 (has links)
Le rayonnement cosmique galactique nucléaire est composé de noyaux de différentes espèces et ses sources sont encore mal identifiées. Cette méconnaissance est en partie due au caractère diffusif de la propagation des noyaux dans les champs magnétiques dont la composante turbulente supprime toute information sur la position des sources. Dans le rayonnement cosmique, on distingue les noyaux pri- maires qui sont principalement créés puis accélérés près de leurs sources des noyaux secondaires, uniquement créés par spallation des primaires plus lourds. La mesure des rapports d'abondance se- condaire sur primaire permet d'étudier les processus de propagation et donc de remonter aux méca- nisme sources du rayonnement cosmique. Cette étude apporte de plus une meilleure compréhension de l'environnement astrophysique galactique. Ce travail nécessite une très bonne connaissance des sections efficaces d'interaction du rayonnement cosmique dans le milieu interstellaire qui régissent la modification des abondances lors de la propagation. La première partie de cette thèse est dédiée à la contrainte des paramètres de propagation du rayonnement cosmique galactique via l'étude des abondances des éléments du quartet (1H,2H,3He,4He). À partir d'une nouvelle estimation des sections efficaces, une analyse statistique a permis de démontrer le potentiel de ces éléments pour contraindre les modèles de propagation du rayonnement cosmique. Ces contraintes restent cependant limitées par la précision statistique des mesures actuelles et justifient la mise en œuvre de nouvelles expériences. La deuxième partie de cette thèse est dédiée à la mesure des abondances avec l'expérience CREAM, une expérience embarquée en ballon. Cette mesure nécessite l'identification des éléments dans le dé- tecteur, le calcul des efficacités des sous-détecteurs, la déconvolution des effets dus aux erreurs sur la mesure de l'énergie ainsi que la prise en compte des effets atmosphériques. Cette analyse des données du 3ième vol de CREAM a permis une estimation des abondances des éléments bore, carbone, azote et oxygène. / The sources of Galactic cosmic-ray (GCR) nuclei are still poorly identified. This is partly due to the diffusive propagation (in turbulent magnetic fields) that erases all directional information about the measured fluxes. The species that are predominantly created and accelerated in the sources are denoted 'primary species'. Those mostly created by spallation of heavier primary species are denoted 'secondary species'. While primary fluxes give access to the source parameters, secondary-to-primary ratios trace propagation processes. Key quantities for such studies are the fragmentation cross sections on the interstellar gas and the measured fluxes and ratios. In the first part of this thesis, we provide new constraints on the Galactic propagation parameters from the quartet elements (1H,2H,3He,4He), relying on a new estimate of their cross sections and an evolved statistical analysis. The derived constraints are competitive with those obtained from the standard B/C ratio analysis. The results are however limited by the precision of current measurements and motivate the development of new experiments. The second part of this thesis is dedicated to the analysis of cosmic-ray fluxes measured with the CREAM balloon-borne experiment. We present the particle identification in the detector, the estimation of efficiencies for each sub-detector, the energy reconstruction, and the atmospheric correction. Applied to the 3rd flight data (CREAM-III), we provide new data points for the boron, carbon, nitrogen and oxygen elements above 100 GeV/n.
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