- The paper redefines the Maunder Minimum timeline by segmenting it into decay (1618–1645), deep minimum (1645–1700), and recovery (1700–1723) phases.
- It employs multiple solar proxies, including Hungarian auroral records and Group Sunspot Numbers, to address discrepancies in previous solar activity indices.
- The study highlights implications for solar cycle modeling and climate impact analyses, linking low solar activity with phenomena like the Little Ice Age.
Redefining the Limit Dates for the Maunder Minimum
The paper by Vaquero and Trigo seeks to critically reassess the timeline traditionally associated with the Maunder Minimum (MM), a period recognized for its remarkably low solar activity that purportedly spanned from 1645 to 1715. This paper emerges from advancements in our understanding of past solar activities and leverages distinct proxies to propose a redefinition of MM's chronological bounds. By advocating for a revised bifurcated characterization of the minimum, the authors suggest the "Deep Maunder Minimum" (DMM) from 1645 to 1700 and the "Extended Maunder Minimum" (EMM) from 1618 to 1723, thus encapsulating transitional phases.
A critical evaluation of solar activity indices, including decadal sunspot numbers, auroral night observations in Hungary, and Group Sunspot Number (GSN) metrics, underpins this research. The authors argue for the limitations inherent in the widely accepted GSN series by Hoyt and Schatten, advocating for recalibrations based on more comprehensive data sets. The Hungarian auroral series serves as a novel proxy, deemed more homogenous and reflective of solar activity prior to the MM. Vaquero and Trigo expose discrepancies between this regional dataset and the conventional auroral catalog provided by Křivský and Pejml, especially in addressing the inhomogeneities post-MM.
By delineating the MM into three distinct periods—decay (1618-1645), deep minimum (1645-1700), and recovery (1700-1723)—the authors furnish a more nuanced comprehension of solar cycles observed during these years. This approach aligns more consistently with contemporary distributions of Grand Minima durations as documented by Usoskin and others, which indicate a bimodal pattern with peaks near 50-60 years for short durations. Some numerical insights accentuated in this paper include the comparable solar activity indices during decay and recovery phases to that of the Dalton Minimum, a lesser-known period with reduced solar output.
The theoretical implications are multifaceted, influencing not only astrophysical models of solar dynamics but also cross-disciplinary explorations into climate and societal impacts during this epoch. Notably, variations in solar irradiance are correlated with climate shifts termed the "Little Ice Age," underscoring potential climatological and agrarian disruptions during the EMM phase.
Future research avenues may pivot towards refining the proxies for solar activity, potentially unraveling other Grand Minima or Maxima episodes. Further archeological and historiographical integration may yield a more coherent image of solar influence across socio-historical contexts. This paper thus contributes substantiative insights into solar physics while inviting interdisciplinary dialogue to fully elucidate the temporal boundaries and implications of the MM.