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On the Probability of Occurrence of Extreme Space Weather EventsBy virtue of their rarity, extreme space weather events, such as the Carrington event of 1859, are difficult to study, their rates of occurrence are difficult to estimate, and prediction of a specific future event is virtually impossible. Additionally, events may be extreme relative to one parameter but normal relative to others. In this study, we analyze several measures of the severity of space weather events (flare intensity, coronal mass ejection speeds, Dst, and greater than 30 MeV proton fluences as inferred from nitrate records) to estimate the probability of occurrence of extreme events. By showing that the frequency of occurrence scales as an inverse power of the severity of the event, and assuming that this relationship holds at higher magnitudes, we are able to estimate the probability that an event larger than some criteria will occur within a certain interval of time in the future. For example, the probability of another Carrington event (based on Dst less than - 850 nT) occurring within the next decade is approximately 12%. We also identify and address several limitations with this approach. In particular, we assume time stationarity, and thus, the effects of long-term space climate change are not considered. While this technique cannot be used to predict specific events, it may ultimately be useful for probabilistic forecasting.
Document ID
20120003491
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Riley, Pete (Predictive Science, Inc. San Diego, CA, United States)
Date Acquired
August 25, 2013
Publication Date
February 23, 2012
Publication Information
Publication: Space Weather
Volume: 10
Issue: S02012
Subject Category
Solar Physics
Funding Number(s)
CONTRACT_GRANT: NNH11CC42C
Distribution Limits
Public
Copyright
Other