Reconstructed sunspot positions in the Maunder minimum based on the correspondence of Gottfried Kirch

Abstract

We present reconstructed sunspot positions based on observations reported in letters between Gottfried Kirch and other contemporary astronomers from AD 1680 to 1709, i.e. in the last decades of the Maunder Minimum. The letters to and from Gottfried Kirch in Latin and German language were compiled and edited by Herbst (2006). The letters (and observations) from Kirch are mostly by Gottfried Kirch, but some also by his 2nd wife Maria M. Kirch (married 1692) and their son Christfried Kirch (born 1694). Using excerpts from the letters, some with drawings, we found some 35 sunspot groups (often for several days in a row or with interruptions) by Kirch and/or his letter partners (in three cases, only the month is given: 1704 Jan, Feb, 1707 Mar, otherwise always the exact dates) -usually one group at a time. We also found 17 explicit spotless days, several of them new (previously without any known observations). We could constrain the heliographic latitude by Bayesian inference for 19 sunspot groups -five of them completely new (one group 1680 May 20-22 from Kirch and Ihle, one to two groups 1680 Jun 15-23 for Kirch, one group 1684 May 6 from Ihle, and one group 1688 Dec 14-15 from Kirch), while the others mostly agree (within 2σ) with previously published values for those dates by others. With these data, we then amend the butterfly diagram for the Maunder Minimum. By comparison of our data with the sunspot group catalog in Hoyt & Schatten (1998), we noticed a number of discrepancies, e.g. that dates for British observers in the Maunder Minimum (Flamsteed, Caswell, Derham, Stannyan, Gray, and Sharp) as listed in Hoyt & Schatten (1998) are their original Julian dates, not converted to the Gregorian calendar (10-11 day offset in Hoyt & Schatten). Most of these modifications also apply to the modified sunspot group catalog in Vaquero et al. (2016). We also present two aurorae observed by the Kirchs in 1707 and 1716.

Solar cycle prediction

“…A major role in this work has been played by a team in Potsdam led by Rainer Arlt (Arlt 2008;Arlt et al 2013;Diercke et al 2015). As a result sunspot positions (butterfly diagrams) have now been reconstructed for the period 1826-1880 from drawings by Schwabe and Spörer (Leussu et al 2016(Leussu et al , 2017; for the period 1749-1796 from drawings by Staudacher (Arlt 2009); for the period 1670-1711 from scattered information (Vaquero et al 2015b;Neuhäuser et al 2018); and for the period 1611-1631 from drawings by Scheiner and Galileo (Arlt et al 2016;Vokhmyanin and Zolotova 2018).…”

Historical sunspot records

“…With the spots moving in twelfths of the disk, the unit was given as "inches" ("Zoll" in German). In other words, the half-rings left of the vertical or north-south line are inches 1-6, the ones on the right-hand side are numbered 7-12 (see, e.g., Neuhäuser et al 2018). This style was mostly used throughout the 18th century.…”

Solar Activity According to Observation Data by Cigoli, Galilei, Colonna, Cologna, and Scheiner in 1612–1614

“…Для того чтобы судить о модах солнечной цикличности [1] на вековых масштабах, необходимо привлекать для научного анализа исторические астрономические архивы [2-4]. В настоящее время ведется активная работа по восстановлению параметров солнечной активности по зарисовкам солнечного диска в XVII и XVIII веках [5][6][7][8][9][10].…”