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Title: The statistics of solar energetic partical events : an important component of space weather
Author: Barnard, Luke
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2013
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This thesis studies aspects of the statistical description of "gradual" solar energetic particle (SEP) events. A database of these events covering the period 1967 - 2007 is constructed, using an event definition designed to exclude the shorter-lived, less intense "impulsive” events. To achieve this, a range of satellite observations of the near-Earth energetic proton flux arc used in conjunction with data. from the McMurdo neutron monitor. Methods are presented to intercalibrate the data from different satellite sources and to estimate the error on event fluences caused by data gaps in the observation sequences. Both SEP event occurrence and total fluonce vary regularly over the Schwabe cycle, although this pattern is often not clear in individual cycles; both are positively linearly correlated over a given period with solar activity, as quantified by the sunspot number SSN, the near-Earth interplanetary magnetic field magnitude Bmag and the total open solar flux F,. The largest fluences occur when solar activity is at its greatest but there is much variability in event fluences at all activity levels. This is discussed in relation to some parameterisations of SEP event statistics that have been employed in engineering models and in other analyses. Because SEP event occurrence is controlled by solar activity, long-term change in space climate may influence the hazards that they pose. An analogue forecast of future space climate, produced by studying past variations in a 9300-year record, shows that solar activity will probably decline rapidly from the grand solar maximum (GSM) that has persisted throughout the space-age. However, data on SEP events outside of GSM conditions are minimal and this is shown to invalidate attempts to predict their occurrence using a combination of Bmag and SSN as a proxy for their occurrence in the past.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available