太陽がスーパーフレアを起こす可能性を示す新たな証拠（Sun: New Evidence of Superflares）

2026-09-10 マックス・プランク研究所

Historical hand-drawn illustration of the large sunspot that was visible on the Sun in April 1947. © Mount Wilson Observatory

＜関連情報＞

• https://www.mpg.de/26963097/sun-new-evidence-of-superflares
• https://royalsocietypublishing.org/rsta/article/384/2329/20250261/483262/Linking-solar-magnetism-extreme-solar-particle
• https://royalsocietypublishing.org/rsta/article/384/2329/20250290/483258/Empirical-flare-energy-limits-for-the-largest

太陽磁気、極端な太陽粒子現象、恒星のスーパーフレアを結びつける Linking solar magnetism, extreme solar particle events and stellar superflares

Valeriy Vasilyev;Ilya Usoskin;Natalie Krivova
Philosophical Transactions of the Royal Society A  Published:10 Sep 2026
DOI:https://doi.org/10.1098/rsta.2025.0261

Abstract

The magnetic field of the Sun drives a wide range of eruptive phenomena, from small-scale nanoflares to large flares and coronal mass ejections. While direct observations of solar activity cover only the past few decades, indirect evidence indicates that the Sun can occasionally produce events orders of magnitude stronger than any recorded ones in the modern era. Two complementary lines of evidence exist. First, extreme solar particle events (ESPEs) have been inferred from prominent spikes in cosmogenic isotope concentrations preserved in precisely dated natural archives such as tree rings and ice cores over the past 15 millennia. Second, high-precision space-borne photometry has revealed superflares on thousands of stars similar to the Sun. Whether these solar and stellar extremes are physically related remains an open question. We summarize the present state of understanding and discuss physical mechanisms that may link them. Although superflares and ESPEs are both extremely energetic manifestations of magnetic energy storage and release, their relationship does not appear to be one-to-one. Their occurrence and energetics probably depend on how magnetic flux and topology govern the partitioning of released energy between radiation, mass ejection and particle acceleration.

過去最大の太陽黒点におけるフレアエネルギーの経験的限界値 Empirical flare energy limits for the largest historical sunspots

Natalie Krivova;Theodosios Chatzistergos;Maria Kazachenko;Emre Işık
Philosophical Transactions of the Royal Society A  Published:10 Sep 2026
DOI:https://doi.org/10.1098/rsta.2025.0290

Abstract

Extreme solar particle events (ESPEs) reveal that the Sun can occasionally produce eruptions significantly more energetic than those observed in the modern era. These events are thought to originate from powerful coronal mass ejections (CMEs), typically associated with large solar flares triggered by magnetic field reconnection in complex active regions (ARs). Stellar observations indicate that Sun-like stars can host ‘superflares’ exceeding 10³⁴ erg roughly once per century, yet it remains uncertain whether the Sun can reach such flare energies. We empirically estimate the upper limit of solar flare energies using statistical relations between flare-ribbon areas and released energy derived from modern observations. By extrapolating these upper-envelope relations to the largest sunspot group recorded since 1859—the Great Sunspot of 8 April 1947—we find that exceptionally large and complex solar ARs could, in principle, produce flares with bolometric energies of a few × 10³⁴ erg.