Speaker
Description
Solar eruptive activity manifests in several forms, the most prominent and well-studied being solar flares, coronal mass ejections (CMEs), and solar energetic particle (SEP) events. However, the upper limits of intensity for these eruptive phenomena remain largely uncertain. To date, only extreme solar particle events (ESPEs) have been identified in cosmogenic isotope records preserved in datable natural archives. In contrast, no definitive evidence has been found for extreme solar flares or CMEs, and it remains unclear whether the Sun is capable of producing such events.
Only a handful of ESPEs have been detected in cosmogenic isotope data spanning the Holocene epoch, suggesting a occurrence rate of approximately once every 1,500 years. Meanwhile, astronomical observations from the Kepler satellite have revealed the presence of superflares on solar-like stars—events that are several orders of magnitude more energetic than those recorded on the Sun. A recent reanalysis of Kepler data indicates that such superflares may occur as frequently as once every 100 years for events with bolometric energy exceeding $10^{34}$ erg.
Both the observed occurrence rates of solar ESPEs and stellar superflares are subject to significant observational biases. In this presentation, we demonstrate that the apparent disagreement in their occurrence frequencies can be naturally explained by the probabilistic nature of solar eruptive events. Using observations from the GOES satellite series and a global network of ground-based neutron monitors, we investigate the conditional probability of observing SEP events given the detection of a solar flare, considering both SEP and flare intensities.
Finally, we propose an analytical model that accurately reproduces observed X-ray solar flare and SEP data and provides a realistic estimate of the ESPE occurrence rate. According to our model, the production of ESPEs does not necessarily require a superflare; rather, strong—but not extreme—solar flares (e.g., >X10-class) may generate ESPEs under highly favorable conditions.
| Do you plan to attend in-person or online? | In-person |
|---|
