Cosmic ray modulation processes in the heliosphere / Vos E.E.

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dc.contributor.author Vos, Etienne Eben en_US
dc.date.accessioned 2012-09-10T16:14:38Z
dc.date.available 2012-09-10T16:14:38Z
dc.date.issued 2011 en_US
dc.identifier.uri http://hdl.handle.net/10394/7266
dc.description Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2012.
dc.description.abstract The solar minimum of 2009 has been identified as an exceptional event with regard to cosmic ray (CR)modulation, since conditions in the heliosphere have reached unprecedented quiet levels. This unique minimum has been observed by the Earth–orbiting satellite, PAMELA, launched in June, 2006, from which vast sets of accurate proton and electron preliminary observations have been made available. These simultaneous measurements from PAMELA provide the ideal opportunity to conduct an in–depth study of CR modulation, in particular charge–sign dependent modulation. In utilizing this opportunity, a three–dimensional, steady–state modulation model was used to reproduce a selection of consecutive PAMELA proton and electron spectra from 2006 to 2009. Thiswas done by assuming full drifts and simplified diffusion coefficients, where the rigidity dependence and absolute value of themean free paths for protons and electrons were sequentially adjusted below 3 GV and 300 MV, respectively. Care has been taken in calculating yearly–averaged current–sheet tilt angle and magnetic field values that correspond to the PAMELA spectra. Following this study where the numerical model was used to investigate the individual effects resulting from changes in the tilt angle, diffusion coefficients, and global drifts, it was found that all these modulation processes played significant roles in contributing to the total increase in CR intensities from 2006 to 2009, as was observed by PAMELA. Furthermore, the effect that drifts has on oppositely charged particles was also evident from the difference between the peak–shaped time profiles of protons and the flatter time profiles of electrons, as is expected for an A < 0 polarity cycle. Since protons, which drift into the heliosphere along the heliospheric current–sheet, haven’t yet reached maximum intensity levels by 2008, their intensities increased notably more than electrons toward the end of 2009. The time and energy dependence of the electron to proton ratios were also studied in order to further illustrate and quantify the effect of drifts during this remarkable solar minimum period. en_US
dc.publisher North-West University
dc.subject Cosmic rays en_US
dc.subject Modulation en_US
dc.subject Heliosphere en_US
dc.subject Solar minimum en_US
dc.subject Particle diffusion en_US
dc.subject Particle drifts en_US
dc.subject Galactic protons en_US
dc.subject Galactic electrons en_US
dc.subject Kosmiese strale en_US
dc.subject Modulasie en_US
dc.subject Heliosfeer en_US
dc.subject Sonminimum en_US
dc.subject Deeltjie diffusie en_US
dc.subject Deeltjie dryf en_US
dc.subject Galaktiese protone en_US
dc.subject Galaktiese elektrone en_US
dc.title Cosmic ray modulation processes in the heliosphere / Vos E.E. en_US
dc.type Thesis en_US
dc.description.thesistype Masters en_US

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    This collection contains the original digitized versions of research conducted at the North-West University (Potchefstroom Campus)

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