Toward a unified picture of solar and stellar activity
TOKUNO Takato, University of Tokyo
Photometric surveys from space telescopes now provide light curves for large samples of solar-type stars, enabling systematic searches for starspots and stellar flares. Comparative studies with the Sun are beginning to clarify the similarity in underlying mechanisms and the contrast in characteristic magnitudes. In this talk I summarize recent progress, including my own results, toward a unified picture of solar and stellar activity. The first part focuses on the mechanisms. Similarities revealed by comparative studies of spot and flare properties provide key constraints on the underlying physics. After reviewing the commonalities discussed in previous work, I present my ongoing study on the universality of the spot–flare connection. We tested whether the same spot-to-flare pathway operates from the Sun to solar-type stars by quantifying flare timing relative to spot evolution in a scale-independent manner. The second part focuses on the magnitude. The fact that even slowly rotating solar-type stars can exhibit much larger activity than the modern Sun motivates the expectation that similarly extreme events may have occurred in the Sun’s past. Such rare extremes are being explored using “non-telescopic” solar proxies. I review representative examples of extreme solar-flare events inferred from these records, and introduce my recent work on an extreme event recorded by solar-origin particles implanted in extraterrestrial material returned by sample-return missions.