Conveners
CD3 - Refining the Sunspot Number Series : challenges and benefits for the Space Climate Community: Orals - Part 1
- Theodosios Chatzistergos (Max Planck Institute for Solar System Research, Göttingen, Germany)
- Ilya Usoskin (University of Oulu)
- Laure Lefevre (Royal Observatory of Belgium)
CD3 - Refining the Sunspot Number Series : challenges and benefits for the Space Climate Community: orals - part 2
- Theodosios Chatzistergos (Max Planck Institute for Solar System Research, Göttingen, Germany)
- Laure Lefevre (Royal Observatory of Belgium)
- Ilya Usoskin (University of Oulu)
Description
The Sunspot Number (SN; Clette and Lefèvre, 2016 ) and Group Number (GN; Chatzistergos et al., 2017) series are the only direct time series (1610- present) that trace the long-term variations of solar activity over the past centuries. These records are crucial not only for solar/stellar physics and space weather studies but also for assessing the Sun's influence on Earth's climate.
While modern observations provide better links with space weather effects, SN and GN remain the longest direct observations of solar activity, and thus, are an indispensable bridge linking past and present solar behavior.
In 2016, an international team led a major update of the existing SN/GN series. However, issues remain and a decade after the release of SN version 2.0, efforts to refine sunspot calibrations continue, leading to several new versions of GN (Clette et al., 2023). Current work is focused on updating the GN database (following Vaquero et al., 2016), culminating in the development of a new SN database for historical data and the subsequent reconstruction of GN and SN, paving the way for version 3.0.
This session welcomes presentations on all aspects of historical sunspot observations, including (but not limited to) analyses of characteristics of the sunspot series, performance of cross-calibration techniques, recovery and correction of historical sunspot records, and also comparisons of sunspot series with other solar activity indices. By exchanging ideas, through presentations and discussions, we can strengthen our collective effort to make both time series more accurate, understandable and accessible to the scientific community.
Understanding long-term solar activity is key for advancing our knowledge of the solar dynamo and improving space climate forecasting capabilities. In this contribution, we present a comprehensive revision of sunspot records from two key periods: the early telescopic era and the decades following the Maunder Minimum.
First, we reanalyze Christoph Scheiner’s observations from Rosa Ursina and...
Parisian solar observations constitute the richest sunspot data set covering the Maunder minimum. Thirty years ago, sunspot latitudes were reconstructed by Elisabeth Nesme-Ribes, but these data have been lost. We present an extensive set of newly reconstructed sunspot parameters for both sunspot groups and individual sunspots. Based on the hand-written notes in the observational journals by...
Within four centuries of instrumental sunspot observations, the Maunder Minimum is known as a unique period with extremely small solar cycles and enhanced hemispheric asymmetry of the reported sunspot groups, as well as the apparent loss of the solar coronal streamers. Sunspot group positions have been discussed mostly on the basis of the French and German observers’ records. Some researchers...
The reconstruction of the Sunspot Number (SN) series is a cornerstone for long-term solar activity studies and space climate research. In recent years, the exploitation of historical solar observations has proven essential for identifying inconsistencies, improving calibration, and extending the SN record. This presentation reviews recent advancements in the use of historical documents—such as...
The extraordinary importance of the sunspot number is given by the fact that it is the longest data series available for the study of the long term behaviour of the solar activity. This is also one of the sources of its weakness because of the calibrational challenge of the datasets recorded in the large number of different time intervals. A further drawback is that it is a dimensionless...
Historical observations play an important role in understanding past solar activity and any changes that may have occurred with respect to the sun. The current state of most historical data is not well-suited for modern data analysis, including artificial intelligence and machine learning. Most data sets are also not well discoverable and are at risk of being lost. This leaves historical data...
Long-term reconstructions of sunspot number (SSN) and group sunspot number (GSN) often tacitly assume that the basic characteristics of solar activity remain unchanged even over long times, e.g., that the sunspots and sunspot groups now and, say, 100 or 500 years ago have the same relations and characteristics. However, this assumption needs examination, especially as the long-term...
The group sunspot number is the longest direct record of solar activity.
However, cross-calibrating the available data from many individual observers poses a challenge.
Several reconstructions of group sunspot numbers exist, based on different cross-calibration strategies.
Beyond this, the methods also vary in how the data are linked across observers.
Some methods rely on sequential...
Efforts have been undertaken by the solar community since 2010 to revise both the Sunspot Number and the Group Number series (SN and GN). I will present our latest achievements and our plans for the near future.
First, since the last revision of SN in 2015, significant progress has been made in recovering and digitizing historical datasets, notably including the Mittheilungen from the...
Sunspot observations made by Rudolf Wolf (1816 - 1893) during the years from 1849 to 1893 form the core of the Wolf series of sunspot number index, the longest directly observed series of solar activity. Homogeneity is considered as the most important property of the Wolf series, since without a stable scale no valid conclusions about variations in the long term progress of solar activity can...
The International Sunspot Number (ISN) series, a cornerstone for space climate studies, still exhibits scale discrepancies despite recent recalibrations, underscoring the critical need for a comprehensive reconstruction from raw historical observations. The FARSuN (Findability and Accessibility of historical Raw Sunspot Numbers) project addresses this by systematically gathering, digitizing,...
Angelo Secchi, a 19th-century Italian Jesuit and pioneering figure in astrophysics, carried out systematic solar observations for over 25 years at the Collegio Romano in Rome.
His original notebooks, documenting observations from 1853 to 1878, have recently been digitized, resulting in over 5,400 high-resolution images.
In this presentation, I will highlight the citizen science project,...
Direct sunspot observations cover about four centuries or about 36 solar cycles, with one-third of them being poorly defined because of the lower quality of observations before 1750. An indirect proxy of solar activity, the abundance of cosmogenic isotopes measured in independently dateable natural archives, such as 14C in tree rings, is the only quantitative method to reconstruct solar...
