Reanalyses of the Sunspot Observations of Fogelius and Siverus: Two "Long-Term" Observers during the Maunder Minimum

Abstract

The solar activity during the Maunder Minimum (MM; 1645 -- 1715) has been considered significantly different from the one captured in modern observations, in terms of sunspot group number and sunspot positions, whereas its actual amplitudes and distributions is still under active discussions. In its core period (1650/1660 -- 1700), Martin Fogelius and Henrich Siverus have formed significant long-term series in the existing databases with numerous spotless days, as the 13th and 7th most active observers before the end of the MM. In this study, we have analysed their original archival records, revised their data, have removed significant contaminations of the apparent "spotless days" in the existing databases, and cast caveats on the potential underestimation of the solar-cycle amplitude in the core MM. Still, they reported at best one sunspot group throughout their observational period and confirm the significant suppressed the solar cycles during the MM, which is also supported from the contemporary observations of Hook and Willoughby. Based on the revised data, we have also derived positions of notable sunspot groups, which Siverus recorded in 1671 (~ N7.5° +/- 2.5°), in comparison with those of Cassini's drawings (~ N10° +/- 1°). Their coincidence in position and chronology in corrected dates indicates these sunspot groups were probably the same recurrent active region (AR) and its significantly long lifespan (>~ 35 days) even during the MM.

18 pages, 5 figures, and 1 table; accepted for publication in the Monthly Notices of the Royal Astronomical Society; Figures 1 and 2 are reserved for the record version

References in corpus (10)

• Visualization of the challenges and limitations of the long-term sunspot number record
• Temporal and Spatial Evolutions of a Large Sunspot Group and Great Auroral Storms around the Carrington Event in 1859
• Level and length of cyclic solar activity during the Maunder minimum as deduced from the active day statistics
• Thaddäus Derfflinger's sunspot observations during 1802-1824: A primary reference to understand the Dalton Minimum
• Increasing Lifetime of Recurrent Sunspot Groups within the Greenwich Photoheliographic Results
• Sunspot latitudes during the Maunder Minimum: a machine-readable catalogue from previous studies
• Sunspot characteristics at the onset of the Maunder Minimum based on the observations of Hevelius
• The Solar Corona during the Total Eclipse on 16 June 1806: Graphical Evidence of the Coronal Structure during the Dalton Minimum
• Reanalyses of the Sunspot Observations of Fogelius and Siverus: Two "Long-Term" Observers during the Maunder Minimum
• Candidate Auroral Observations during the Major Solar-Terrestrial Storm in May 1680: Implication for Space Weather Events during the Maunder Minimum

Cited by in corpus (6)

• Re-calibration of the Sunspot Number: Status Report
• Strong evidence of low levels of solar activity during the Maunder Minimum
• Reanalyses of the Sunspot Observations of Fogelius and Siverus: Two "Long-Term" Observers during the Maunder Minimum
• Daniel Mögling's sunspot observations in 1626 - 1629: A manuscript reference for the solar activity before the Maunder Minimum
• Long-lived sunspots in historical records: a case study analysis from 1660 to 1676
• Sunspot Observations in 1684-1702: John Flamsteed and Philippe de La Hire