Sunspot observations by Charles Malapert during the period 1618–1626: a key data set to understand solar activity before the Maunder minimum

Abstract

A revision is presented of the sunspot observations made by Charles Malapert from 1618 to 1626, studying several documentary sources that include those observations. The revised accounting of the group numbers recorded by Malapert for that period shows new information unavailable in the current sunspot group data base. The average solar activity level calculated from these revised records of Malapert is by almost one-third greater than that calculated from his records included in the current group data base. Comparison of the sunspot observations made by Malapert and by other astronomers of that time with regard to the number of recorded groups and sunspot positions on the solar disc shows good agreement. Malapert reported that he only recorded one sunspot group in each sunspot drawing presented in Austriaca Sidera Heliocyclia (the documentary source that includes most of the sunspot records made by Malapert), although he sometimes observed several groups. Therefore, the sunspot counts obtained in this work on Malapert's sunspot observations represent the lower limit of the solar activity level corresponding to those records.

Daniel Mögling’s Sunspot Observations in 1626–1629: A Manuscript Reference for the Solar Activity before the Maunder Minimum

“…Temporal variations in their latitudinal distributions show their migration to lower heliographic latitudes towards 1629. This result, which agrees fairly well with the existing distributions of contemporary sunspot observations by Scheiner (Arlt et al, 2016) and Malapert et al (Carrasco et al, 2019b), visualises sunspot migration during the declining phase of Solar Cycle −12. This confirms the hypothesis of the continuity of Solar Cycle −12 from 1621 to somewhere in 1631/1632 (Vokhmyanin and Zolotova, 2018b;Carrasco et al, 2019b).…”

“…Mögling actively recorded spotless days in 1626 -1627 and may further benefit future analyses in ADFs in combination with other contemporary observations. Mögling's data compare well with contemporary observations (e.g., Vaquero et al, 2016;Carrasco et al, 2019b), as shown in Figure 3. Here, we have also consulted the records of Hortensius and Schickard, who were based at the Protestant cities of Leiden and Tübingen that used the Julian calendar at that time, to revise their observational data.…”

“…This enabled us to derive the minor sunspot groups whose motions were not tracked by Mögling himself in his manuscript ULBD HS 228. Figure 4: Sunspot positions in 1620 -1629, consisting of the sunspot observations of Scheiner (Arlt et al, 2016), Malapert et al (Carrasco et al, 2019b), and Mögling (this study).…”

“…Even after the compilation of the revised database for historical sunspot observations (V+16), such reanalyses are ongoing efforts that have modified a number of historical observational datasets (e.g., Arlt, 2018;Hayakawa et al, 2018aHayakawa et al, , 2018bCarrasco et al, 2019aCarrasco et al, , 2019bKaroff et al, 2019), including long-term observations around the Maunder Minimum (e.g., Carrasco et al, 2019c;Hayakawa et al, 2020aHayakawa et al, , 2021 and the Dalton Minimum (Hayakawa et al, 2020b). Sunspot drawings of the early 17th century are of particular interest, as they provide unique evidence for the solar activity before the Maunder Minimum, and moderate revisions or additions can update the existing understanding (e.g., Vaquero et al, 2011;Carrasco et al, 2019a).…”

“…Sunspot drawings of the early 17th century are of particular interest, as they provide unique evidence for the solar activity before the Maunder Minimum, and moderate revisions or additions can update the existing understanding (e.g., Vaquero et al, 2011;Carrasco et al, 2019a). To date, the major observers' observational records before the Maunder Minimum have been recently analysed to improve sunspot group number and derive sunspot positions (Arlt et al, 2016;Zolotova, 2018a, 2018b;Carrasco et al, 2019aCarrasco et al, , 2019bCarrasco et al, , 2020Vokhmyanin et al, 2020Vokhmyanin et al, , 2021.…”