Modeling the highly energetic particles known as galactic cosmic rays is a highly nontrivial task. This process may require numerical simulations of the complex processes occurring continuously in the heliosphere due to changes in solar wind reflecting the solar activity. However, if reasonable assumptions are employed, considering only the diffusion and convection processes, the above phenomenon can be reduced to a simplified scenario that can be modeled analytically. The variable solar wind may be responsible for solar modulation of galactic cosmic rays. The aforementioned, in addition to the postulated role of cosmic rays in climate change, has led to the following questions: what is the relationship between galactic cosmic rays and solar wind? What are the possible effects of solar wind on galactic cosmic ray flux? In an attempt to address these questions, we have modeled the transport of galactic cosmic rays in the heliosphere theoretically. Our model describes solar modulation and transport of galactic cosmic rays in the heliosphere mainly in terms of the size of the heliosphere, timedependent solar wind, and a uniform diffusion coefficient. Our results suggest that solar wind causes significant decrease in galactic cosmic ray flux at r ≈ 1AU. In further investigation, we examine a short-time variation of the calculated flux, and the result is reflected by exposing a negative correlation of −0.988 ± 0.001 between galactic cosmic ray flux variation and the solar wind variation at r ≈ 1AU. This outcome may suggest that the higher the solar wind, the lower the galactic cosmic ray flux and vice-versa. For completeness, we compared our results with available observational data that shows a good fit to the model. Thus, based on our model results, it may be possible to predict that galactic cosmic ray flux variation and solar wind variation at Earth are negatively correlated.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:685275 |
| Date | January 2016 |
| Creators | Ihongo, Grace Dominic |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=229511 |
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