Variation of solar cyclicity during the Spoerer Minimum

We investigate the 11-year solar cycle during the Spoerer Minimum (1415-1534 A.D.) by measuring the carbon 14 content in the annual tree rings for the period 1413-1554 A.D. The period of the Spoerer Minimum is assumed to be a prolonged sunspot minimum like the Maunder Minimum (1645-1715 A.D.). However, the 11-year solar cycle, which appears in recent solar variations, was also prominently detected in the carbon 14 record during this period. The amplitude of the 11-year cycle seems to have been modulated only around 1455-1510 A.D.