# Probability of a Large Coronal Mass Ejection Hitting Earth

Below is one of the interesting sources I used in my research when I wrote my thriller Patriarch Run. The science behind the vulnerability of our power grid is not only fascinating, it is truly frightening. According to physicist Pete Riley, whose conclusion NASA has quoted on its website, the probability that a coronal mass ejection (CME) the size of the Carrington Event will hit Earth is 12% per decade. Many scientists believe that our dependence on electronics creates a vulnerability so huge that an event like this could pose a threat to civilization. In other words, 12% per decade are odds I don't like.

A mid-level solar flare. Courtesy of NASA.

What follows is the abstract of Pete Riley's, 23 February 2012, paper On The Probability Of Occurrence Of Extreme Space Weather Events.

By 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 >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 < −850 nT) occurring within the next decade is ∼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.

### Benjamin Dancer

Benjamin is the author of the literary thriller Patriarch Run, the first book in a series that will include Fidelityand The Story of the Boy. He also writes about parenting, education, sustainability and national security.

Benjamin works as an Advisor at a Colorado high school where he has made a career out of mentoring young people as they come of age. His work with adolescents has informed his stories, which are typically themed around fatherhood and coming-of-age.

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