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dc.contributor.advisorPotgieter, M.S.
dc.contributor.advisorFerreira, S.E.S.
dc.contributor.authorStrauss, Roelf du Toit
dc.date.accessioned2014-03-07T08:42:04Z
dc.date.available2014-03-07T08:42:04Z
dc.date.issued2013
dc.identifier.urihttp://hdl.handle.net/10394/10217
dc.descriptionPhD (Space Physics), North-West University, Potchefstroom Campus, 2013
dc.description.abstractThe transport of cosmic rays in the heliosphere is studied by making use of a newly developed modulation model. This model employes stochastic differential equations to numerically solve the relevant transport equation, making use of this approach’s numerical advantages as well as the opportunity to extract additional information regarding cosmic ray transport and the processes responsible for it. The propagation times and energy losses of galactic electrons and protons are calculated for different drift cycles. It is confirmed that protons and electrons lose the same amount of rigidity when they experience the same transport processes. These particles spend more time in the heliosphere, and also lose more energy, in the drift cycle where they drift towards Earth mainly along the heliospheric current sheet. The propagation times of galactic protons from the heliopause to Earth are calculated for increasing heliospheric tilt angles and it is found that current sheet drift becomes less effective with increasing solar activity. Comparing calculated propagation times of Jovian electrons with observations, the transport parameters are constrained to find that 50% of 6 MeV electrons measured at Earth are of Jovian origin. Charge-sign dependent modulation is modelled by simulating the proton to anti-proton ratio at Earth and comparing the results to recent PAMELA observations. A hybrid cosmic ray modulation model is constructed by coupling the numerical modulation model to the heliospheric environment as simulated by a magneto-hydrodynamic model. Using this model, it is shown that cosmic ray modulation persists beyond the heliopause. The level of modulation in this region is found to exhibit solar cycle related changes and, more importantly, is independent of the magnitude of the individual diffusion coefficients, but is rather determined by the ratio of parallel to perpendicular diffusion.en_US
dc.language.isoenen_US
dc.publisherNorth-West University
dc.subjectCosmic raysen_US
dc.subjectHeliosphereen_US
dc.subjectMagneto-hydrodynamicsen_US
dc.subjectStochastic differential equationsen_US
dc.subjectJovian electronsen_US
dc.subjectCharge-sign dependent modulationen_US
dc.subjectHeliopauseen_US
dc.subjectHeliospheric current sheeten_US
dc.subjectPropagation timesen_US
dc.subjectParticle driftsen_US
dc.subjectEnergy lossesen_US
dc.subjectKosmiese straleen_US
dc.subjectHeliosfeeren_US
dc.subjectMagneto-hidrodinamikaen_US
dc.subjectStogastiese differentiaalvergelykingsen_US
dc.subjectJupiter elektroneen_US
dc.subjectLadingsafhanklike modulasieen_US
dc.subjectHeliopouseen_US
dc.subjectHeliosferiese neutrale vlaken_US
dc.subjectVoortplantingstyeen_US
dc.subjectDeeltjie dryfen_US
dc.subjectEnergie verlieseen_US
dc.titleModelling of cosmic ray modulation in the heliosphere by stochastic processesen
dc.typeThesisen_US
dc.description.thesistypeDoctoralen_US
dc.contributor.researchID10713158 - Ferreira, Stephanus Esaias Salomon (Supervisor)


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