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![Red crosses and blue circles define the rotation angle of an image (a), the observation time (b), the average dispersion of all sunspots on a drawing from their average latitudes (c), all calculated by Methods I and II, correspondingly. Light blue curves mark P−q\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$P-q$\end{document} limits when the Sun is above horizon. Black curves denote time of sunrise and sunset.](publication/339820711/figure/fig4/AS:962171085283359@1606410871810/Red-crosses-and-blue-circles-define-the-rotation-angle-of-an-image-a-the-observation.png)
Red crosses and blue circles define the rotation angle of an image (a), the observation time (b), the average dispersion of all sunspots on a drawing from their average latitudes (c), all calculated by Methods I and II, correspondingly. Light blue curves mark P−q\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$P-q$\end{document} limits when the Sun is above horizon. Black curves denote time of sunrise and sunset.
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The reconstruction of sunspot parameters in the early era of telescopic observations extends our knowledge on visual sunspot activity up to 400 years into the past. 200 digital solar images from 18 December 1610 to 28 January 1613 by the English astronomer Thomas Harriot were analyzed to yield sunspot counts, areas and positions. Harriot generally...
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Citations
... Systematic sunspot observations have been carried out only since the beginning of the 17th century with the use of telescopes as astronomical instruments (Vaquero & Vázquez 2009;Arlt & Vaquero 2020). Thus, the first known telescopic sunspot record was made by Harriot in 1610 December, and then, other records were made by Scheiner, Galileo, Malapert, Mögling, and others (Herr 1978;Neuhäuser & Neuhäuser 2016;Carrasco et al. 2019aCarrasco et al. , 2020Carrasco et al. , 2022bVokhmyanin et al. 2020Vokhmyanin et al. , 2021Hayakawa et al. 2021a). ...
The Maunder Minimum was a period with significantly reduced solar activity between 1645 and 1715, approximately. The transition between the low solar activity in the Maunder Minimum and the subsequent “normal” regime of solar activity was gradual. However, there are discrepancies in the solar activity level from sunspot number indices and solar activity proxies in that period. Among the contemporaneous observers, Johann L. Rost and Sebastian Alischer were two key sunspot observers to understand the solar activity in this transition just after the Maunder Minimum. We have revised all their sunspot records, counting the number of groups and individual sunspots to derive reliable data for the solar activity level for the period 1716–1726. We found significant misinterpretations of the sunspot group counting assigned to these astronomers in the existing group number databases. Our new group sunspot counting significantly reduces the number of groups for Rost and Alischer’s observations compared to entries in existing databases. Furthermore, our sunspot number estimates (obtained from the active day fraction methodology) of the maximum amplitude of Solar Cycles −3 and −4 are significantly lower than the amplitudes according to the official sunspot number, but they are compatible with sunspot number values obtained from solar activity proxies such as radioisotopes. Our result would imply that solar activity after the Maunder Minimum recovered more gradually and with a lower intensity than previously considered.
... However, incomplete records exist back to 1610 (e.g. Vokhmyanin, Arlt, and Zolotova, 2020;Arlt and Vaquero, 2020;Usoskin, 2023). • Cosmogenic isotopes. ...
The open solar flux (OSF) is the integrated unsigned magnetic flux leaving the top of the solar atmosphere to form the heliospheric magnetic field. As the OSF modulates the intensity of galactic cosmic rays at Earth, the production rate of cosmogenic isotopes – such as ¹⁴C and ¹⁰Be stored in tree rings and ice sheets – is closely related to the OSF. Thus on the basis of cosmogenic isotope data, OSF can be reconstructed over millennia. As sunspots are related to the production of OSF, this provides the possibility of reconstructing sunspot number (SSN) and hence properties of the solar cycles prior to the first sunspot telescopic observations in 1610. However, while models exist for estimating OSF on the basis of SSN, the hysteresis present in OSF and the lack of a priori knowledge of the start/end dates of individual solar cycles means that directly inverting these models is not possible. We here describe a new method that uses a forward model of OSF to estimate SSN and solar cycle start/end dates through a Monte Carlo approach. The method is tested by application to geomagnetic reconstructions of OSF over the period 1845-present, and compared to the known SSN record for this period. There is a substantial improvement in reconstruction of both the SSN time series and the solar cycle start/end dates compared with existing OSF-SSN regression methods. This suggests that more accurate solar-cycle information can be extracted from cosmogenic isotope records by forward modelling, and also provides a means to assess the level of agreement between independent SSN and OSF reconstructions. We find the geomagnetic OSF and observed SSN agree very well after 1875, but do differ during the early part of the geomagnetic record, though still agree within the larger observational uncertainties.
... Regular monitoring of the solar surface performed with telescopes has been carried out since the early 17th century when Galileo Galilei, Thomas Harriot, Christoph Scheiner, and their contemporaries performed the first telescopic sunspot observations (e.g., Galilei 1613;Scheiner 1630;Herr 1978;Neuhäuser & Neuhäuser 2016;Arlt & Vaquero 2020;Carrasco et al. 2020Carrasco et al. , 2022Vokhmyanin et al. 2020). These early observations (Vaquero & Vázquez 2009) revealed that the Sun has sunspots, which move across the solar disk due to the solar rotation. ...
Angelo Secchi, an Italian Jesuit and prominent scientist of the 19th century, and one of the founders of modern astrophysics, observed the Sun regularly at the Collegio Romano in Rome, Italy, for more than 25 yr. Results from his observations are reported in articles published in the scientific journals of the time, as well as in drawings and personal notebooks that are stored in the historical archive of the Istituto Nazionale di Astrofisica Osservatorio Astronomico di Roma. The latter material, which reports solar observations performed from 1853–1878, includes original documents from Secchi and from a few of his close collaborators. The above unique material has recently been digitized for preservation purposes and for allowing the scientific exploitation of data not easily accessible so far. A total of more than 5400 digital images have been produced. Here we present the archival material and the new digital data derived from it. We also present results obtained from our primary analysis of the new digital data. In particular, we produced new measurements of the group number from 1853–1878, which will be available for future recalibration of the group number series.
... Sunspots are the observable dark areas that emerge on the surface of the Sun due to relatively lower temperatures in that specific region than the other regions. Since 1610, astronomers have observed the solar surface with the help of telescopes and recorded the occurrence and appearance of sunspots (Vokhmyanin, Arlt, and Zolotova, 2020). As per the study of V. Kumar rt.vipink@gmail.com A. Kumar abhijeetk235@gmail.com 1 Informer, and LSTM where the Informer model outperformed all other models. ...
A multi-layer, deep-learning (DL) architecture consisting of stacked Convolutional Long Short Term Memory (sConvLSTM1D) layers is proposed to forecast the sunspot number (SSN) more effectively. The proposed model with optimized hyper-parameters performs efficiently on four kinds of sunspot data with different frequencies of time that are yearly, monthly, daily, and 13-month smoothed provided by the World Data Center-Sunspot Index and Long Term Solar Observation (WDC-SILSO), the Royal Observatory of Belgium (SILSO World Data Center). The model was contrasted with other traditional DL models on different performance metrics, namely root-mean-square error (RMSE), mean-absolute error (MAE), mean-absolute-percentage error (MAPE), and mean-absolute-scaled error (MASE). A non-parametric statistical test has also been carried out to confirm the model’s effectiveness. The prediction of the highest yearly mean of total sunspot number (SSN) in Solar Cycle 25 (SC25) has also been performed. The proposed sConvLSTM1D model suggests that the solar cycle exhibits the characteristics of a weak cycle. However, it is anticipated to be stronger than the preceding Solar Cycle 24 (SC24). The year of peak sunspot number will be 2024, as per the prediction, with the peak value of yearly mean sunspot number as 140.84, which is 24.3% higher than the peak value of the yearly mean of total sunspot number, which was 113.3 in the Solar Cycle 24 in the year 2014.
... However, incomplete records do exist back to 1610 (e.g. Vokhmyanin, Arlt, and Zolotova, 2020;Arlt and Vaquero, 2020;Usoskin, 2023). ...
The open solar flux (OSF) is the integrated unsigned magnetic flux leaving the top of the solar atmosphere to form the heliospheric magnetic field (HMF). As the HMF modulates the intensity of galactic cosmic rays at Earth, the production rate of cosmogenic isotopes – such as ¹⁴ C and ¹⁰ Be stored in tree rings and ice sheets – is closely related to the OSF. Sunspots are related to the production of OSF and this provides the possibility of converting OSF to sunspot number (SSN) in order to reconstruct properties of the solar cycles prior to the first sunspot telescopic observations in 1610. While models exist for estimating OSF on the basis of sunspot number, the hysteresis present in OSF and the lack of a priori knowledge of solar cycle phase means that inverting these models is not possible. We here describe a new method that uses a forward model of OSF to estimate SSN and solar cycle phase through a Monte Carlo approach. The method is tested by application to geomagnetic reconstructions of OSF over the period 1850-present and comparison to the known SSN. There is a substantial improvement in reconstruction of both the SSN time series and the solar cycle start dates compared with a simple OSF-SSN regression. This suggests more accurate solar cycle information can be extracted from annual cosmogenic isotope records by this method.
... Although both methods adjust the orientation of the heliographic grid omitting the longitudinal displacement of sunspots, we recommend relying on longitudes provided by Method I. Longitudes are measured from the zero meridian of the heliographic longitudes at Greenwich noon on 1 January 1854 and rotating with a sidereal period of 25.38 days as conventionally ҥxed by Carrington (Meeus, 1991). The mathematical procedure is described in detail in Vokhmyanin and Zolotova (2018); Vokhmyanin, Arlt, and Zolotova (2020), where we also describe approaches to cluster sunspots into groups based on the classiҥcation by McIntosh (1990) and to measure sunspot areas in millionths of a solar hemisphere (microhemispheres, msh). (Eimmart Archive Coll. ...
Digital images of sunspot drawings of the archives of Georg Christoph Eimmart stored at the National Library of Russia are analyzed to obtain sunspot group numbers and sunspot areas as well as heliographic positions. Overall, more than a hundred drawings were processed. The impact of drawing and reproduction uncertainties and of the aims of historical observations are considered. The sunspot positions are compared to those reported by contemporary astronomers of the Maunder minimum. The restored sunspot group numbers and latitudes are compared to those extracted by Hoyt and Schatten as well as Hayakawa et al. The persistence of long-lived sunspots over several solar rotations is discussed.
... Thomas Harriot recorded the earliest sunspot drawing that was based on telescopic observation in 1610. Vokhmyanin, Arlt, and Zolotova (2020) revised Harriot's sunspotgroup number and reconstructed butterfly diagrams on the basis of copies of his original manuscript. Shortly afterward, in 1611, Galilei and Scheiner started their sunspot observations. ...
We report progress on the ongoing recalibration of the Wolf sunspot number ( $S_{\mathrm{N}}$ S N ) and group-sunspot number ( $G_{\mathrm{N}}$ G N ) following the release of version 2.0 of $S_{\mathrm{N}}$ S N in 2015. This report constitutes both an update of the efforts reported in the 2016 Topical Issue of Solar Physics and a summary of work by the International Space Science Institute (ISSI) International Team formed in 2017 to develop optimal $S_{\mathrm{N}}$ S N and $G_{\mathrm{N}}$ G N reconstruction methods while continuing to expand the historical sunspot-number database. Significant progress has been made on the database side while more work is needed to bring the various proposed $S_{\mathrm{N}}$ S N and (primarily) $G_{\mathrm{N}}$ G N reconstruction methods closer to maturity, after which the new reconstructions (or combinations thereof) can be compared with (a) “benchmark” expectations for any normalization scheme (e.g., a general increase in observer normalization factors going back in time), and (b) independent proxy data series such as F10.7 and the daily range of variations of Earth’s undisturbed magnetic field. New versions of the underlying databases for $S_{\mathrm{N}}$ S N and $G_{\mathrm{N}}$ G N will shortly become available for years through 2022 and we anticipate the release of the next versions of these two time series in 2024.
... Thomas Harriot recorded the earliest sunspot drawing that was based on telescopic observation in 1610. Vokhmyanin et al. (2020) revised Harriot's sunspot group number and reconstructed butterfly diagrams on the basis of copies of his original manuscript. Shortly afterward, in 1611, Gallilei and Scheiner started their sunspot observations. ...
We report progress on the ongoing recalibration of the Wolf sunspot number (SN) and Group sunspot number (GN) following the release of version 2.0 of SN in 2015. This report constitutes both an update of the efforts reported in the 2016 Topical Issue of Solar Physics and a summary of work by the International Space Science Institute (ISSI) International Team formed in 2017 to develop optimal SN and GN re-construction methods while continuing to expand the historical sunspot number database. Significant progress has been made on the database side while more work is needed to bring the various proposed SN and (primarily) GN reconstruction methods closer to maturity, after which the new reconstructions (or combinations thereof) can be compared with (a) ``benchmark'' expectations for any normalization scheme (e.g., a general increase in observer normalization factors going back in time), and (b) independent proxy data series such as F10.7 and the daily range of variations of Earth's undisturbed magnetic field. New versions of the underlying databases for SN and GN will shortly become available for years through 2022 and we anticipate the release of next versions of these two time series in 2024.
... This led to extensive efforts to recover new data and to correct mistakes in the digital databases of old sunspot records (e.g. Arlt et al. 2013Arlt et al. , 2016Vaquero et al. 2016;Carrasco et al. 2018Carrasco et al. , 2019Carrasco et al. , 2021aHayakawa et al. 2020aHayakawa et al. ,b, 2021aVokhmyanin et al. 2020;Bhattacharya et al. 2021). Sunspot number series were also drastically updated and scrutinized leading to a new version of ISNv2 (Clette and Lefèvre 2016) and a number of alternative group sunspot number (GSN) series (e.g. ...
The Sun provides most of external energy to Earth’s system and thus has the potential of influencing it. Various studies reported a correlation between the solar cycle length and the northern hemisphere temperatures on Earth. Here, we reassess the cycle length record by incorporating the newly revised and updated sunspot number series as well as plage area composite, before comparing it to Earth temperature records. We find that cycle length series constructed from sunspot and plage data exhibit the same behaviour, both showing a downward trend after 1940. Our results suggest that the agreement between solar cycle lengths and temperatures found earlier is an artefact of (1) some arbitrary choices made by those studies when constructing the cycle length series as well as (2) a rather short time interval, to which the analyses were restricted. When considering the entire period of reliable sunspot and temperature data, these records diverge before about 1870 and after 1960. We also find a poor agreement between Earth temperatures and cycle length when using plage areas instead of sunspot data to derive cycle lengths. Our result of the divergence between cycle length series and Earth’s temperature after 1960 implies that the cycle length cannot be used to support a solar origin for the warming on Earth over the last 5 decades.
... These observations have offered various scientific insights ranging from solar physics to the solar-terrestrial environment (Charbonneau, 2020;Clette et al., 2014;Hathaway, 2015;Usoskin, 2017). These records are based on sunspot observations of multiple individual observers beginning in 1610 (Arlt & Vaquero, 2020;Clette et al., 2014;Vaquero et al., 2016;Vokhmyanin et al., 2020) and have been actively subjected to recalibration with multiple methodologies resulting in somewhat controversial outputs (Chatzistergos et al., 2017;Cliver, 2016;Cliver & Ling, 2016;Svalgaard & Schatten, 2016;Usoskin et al., 2016Usoskin et al., , 2021, as partially reviewed in Muñoz-Jaramillo and . In this context, it is extremely important to revisit the data and add the original sunspot observations, including modern records, owing to several controversial issues such as sunspot number weighting and different observational methods Svalgaard et al., 2017). ...
Individual sunspot observations have formed a ground basis of international sunspot number, a unique reference for long‐term solar variability in the centennial timescale. The original datasets were subjected to exploitations and analyses upon the recalibrations of the sunspot number series. In this context, this study reviewed and analysed original sunspot records and their databases in the Kawaguchi Science Museum (KSM) in Japan. KSM hosts sunspot drawings and logbooks from 1972 to 2013. This dataset has a longer chronological coverage than what was known to the scientific community (1981–2010). These records have been digitized and publicized in a museum database, which allows users to access individual sunspot drawings and numerical data in KSM logbooks. These records are highly homogeneous as a single observer's dataset (Hitoshi Takuma), who used a 15‐cm refractor at the Kawaguchi Juvenile Museum in 1972–2003 and a 20‐cm refractor at KSM in 2003–2013. We also reviewed the Takuma data series, his monthly observation days (21.3 days/month), sunspot number in the whole disk and each hemisphere, and sunspot positions in a butterfly diagram. We also assessed Takuma's data stability in comparison with the international sunspot number and reference datasets of the SILSO. Takuma's data appear stable until 2003, when he changed the observation site and instrument. His data stability was quantitatively compared with the SILSO reference datasets, confirming the substantial long‐term stability of the data and establishing its reliability as an alternative reference for sunspot number recalibration. This article visualises a database for Hitoshi Takuma's sunspot observations and background metadata.
