Sunspots change in quantity relying on how a lot magnetic exercise the solar dynamo generates. However there’s not total chaos: These adjustments happen in a cycle, which lasts about 11 years on common. The sun additionally experiences prolonged durations of low exercise that may final for many years, known as grand minima. The Maunder minimal, which occurred between 1645 and 1715, is commonly considered as an archetypal instance of the sun’s habits throughout these irregular durations.
Historic knowledge on the sun’s habits throughout the Maunder minimal, together with information of sunspot exercise and radionuclide deposition, are sparse and don’t at all times align. To bolster information of the solar dynamo throughout the Maunder minimal, Limei Yan and colleagues turned to a brand new supply of knowledge: observations of equatorial aurorae in Korean historic texts.
Korean historians stored meticulous information of occasions throughout the Joseon dynasty, which spanned the 14th to nineteenth centuries. These information embody observations of the evening sky, comparable to aurorae, which might be seen usually throughout a lot of the Joseon dynasty due to a geomagnetic anomaly within the west Pacific. Aurorae are correlated with the solar cycle and occur extra incessantly in periods of excessive exercise.
The researchers used an current database of Korean historic information to research a set of 1,012 aurorae between 1620 and 1810. By noting when aurorae occurred extra and fewer incessantly, they discovered a comparatively quick, 8-year solar cycle throughout the Maunder minimal. Their paper is revealed within the journal AGU Advances.
Their work provides to different sources of knowledge on the sun’s exercise and supplies proof that the solar cycle was quickly shortened throughout the Maunder minimal. This modification may point out that the solar dynamo enters a definite cyclic mode throughout grand minima, although why that’s stays unclear.
Extra info:
Limei Yan et al, The 8‐12 months Photo voltaic Cycle Throughout the Maunder Minimal, AGU Advances (2023). DOI: 10.1029/2023AV000964
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Aurora information reveal shortened solar cycle throughout Maunder minimal (2023, October 10)
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