Collaborative Research: PREEVENTS Track 2: Quantifying the Risk of Extreme Solar Eruptions (QUEST)

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Solar activity is the primary driver of severe space weather at Earth. The potentially most dangerous events are eruptive X-class flares/Coronal Mass Ejections (CME) that can cause major geomagnetic storms and hazardous solar energetic particles. The 1859 "Carrington" event, if it were to happen in the present day, would cause significant damage to our technological infrastructure. Extreme solar eruptions of similar magnitude to the Carrington event have occurred in the space age, but fortunately were not primarily Earth directed. Observations of other stars, and glimpses into our past using measurements of cosmogenic radioactive nuclides, suggest that even more violent eruptions may be possible. The driver for all of these events is magnetic energy that is stored in powerful solar active region magnetic fields and then explosively released. This project will (1) fundamentally enhance our understanding of the regions that produce extreme solar eruptions, and (2) identify the conditions that foreshadow imminent extreme events and their possible magnitude. To make the science accessible to the general public, the team will leverage and enhance an ongoing partnership between the Community Coordinated Modeling Center and the American Natural History Museum of New York to provide compelling visualizations for high-impact public shows. This project will support the dissertation research of a PhD student at the University of Hawaii and thus contribute to the educational goals of NSF. This research focuses on five science questions: What determines how much energy can be stored to drive major solar eruptions? What determines the fraction of stored energy that is released in these eruptions? What is the largest possible eruption, based on known solar active regions? What roles do multiple eruptions play in maximizing geoeffective structures? What is the statistical likelihood of Carrington-like or greater size eruptions? These questions will be addressed using nonlinear force-free field models, magnetohydrodynamic simulations, analytic flux-rope models, and the theory of partially open fields to investigate eruptions for some of the largest and most complex ARs that have been observed during the space age. By propagating the associated CMEs to Earth's orbit, the maximum values will be inferred for space-weather relevant parameters that the most extreme events can produce at Earth. Magnetic data from solar active regions spanning four decades will be used to bound the size of the largest eruption for known regions. Finally, statistical techniques (previously used to estimate the occurrence-probability of extreme geomagnetic storms) will be employed to calculate the probability of a Carrington-like or worse solar eruption in a given decade.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.