Mind the Gap: New Precise ¹⁴C Data Indicate the Nature of Extreme Solar Particle Events

Abstract

The Sun is known to produce sporadic eruptive events, such as flares and coronal mass ejections (CMEs) when a large amount of energy is released nearly instantly. Such events can cause serious consequences in the Earth's environment, including geomagnetic disturbances, disruptions of radio communications. They can also accelerate charged particles to high energies, producing solar energetic particles (SEPs) that may cause radiation storms at and near-Earth (Desai & Giacalone, 2016;Shea & Smart, 2012;Vainio et al., 2009). The strength of such events may vary as known from instrumental observations during the past decades, including severe storms with hazardous consequences. On the other hand, the era of direct instrumental observation is relatively short, covering several decades, and the experimental data do not allow us to assess the maximum strength of such events nor the probability of their occurrence. The strongest solar particle storm (solar particle event-SPE) directly recorded by ground-based detectors took place on February 23, 1956, while the strongest SPE in the near-Earth space was recorded on

Extreme solar events

“…7.8) that solar SEP events might be harboring a dragon-king. At present, however, the most likely (Occam's razor) conclusion is that they do not (Usoskin and Kovaltsov 2021).…”

Cosmogenic radiosulfur tracking of solar activity and the strong and long-lasting El Niño events

“…As the primary energy source of the solar system, the Sun controls the Earth’s climate and hydrological system and surface radiative energy budget and is crucial in sustaining life and Earth’s habitability ( 1 – 5 ). The solar forcing of changes in Earth’s atmosphere (from the exosphere to surface) is an active area of research in Earth and space sciences.…”

“…1 A ). Relatively long-lived cosmogenic radionuclides (e.g., 14 C and 10 Be) in geochemical proxies such as tree rings and ice cores are utilized to reconstruct past solar activity and geomagnetic field strength ( 1 – 6 ). Yearly resolved anomalies were attributed to strengthened GCRs modulated by abrupt declines in solar activity or increased fluxes of accelerated high-energy atomic nuclei from high-energy astronomical events such as solar proton events (SPEs) and supernovae (SNe) ( 2 , 4 ), which may potentially lead to mass extinction events ( 7 ).…”

“…Measurements in the modern atmosphere are important for developing this model. The short atmospheric residence time of aerosols relative to 14 CO 2 is important for tracking solar activity ( 2 , 3 ), and measurements of aerosol-bound cosmogenic radionuclides such as 7 Be and 10 Be have been widely utilized ( 6 , 8 ). Modeling their transport in the atmosphere is, however, challenging because it is inadequately understood how these radionuclides preferentially attach to chemical complex aerosol components such as sulfates ( 6 ).…”

“…Compared to the long half-lived 10 Be (1.39 million y), which creates a large background in the stratosphere and limits event detection, the shorter half-life of 35 S enables more resolved analysis of the solar cycle. Radiosulfur is hitherto overlooked in solar activity studies ( 2 , 3 , 8 , 9 ) because of analytical difficulties. Using a newly developed analytical method ( 11 ), we present multiyear measurements of atmospheric 35 SO 4 in submicrometer aerosols collected from Southern California to show its response to the most recent solar cycle ( Materials and Methods ).…”