Long-term Datasets for the Understanding of Solar and Stellar Magnetic Cycles (IAU S340) Proceedings of the 340th Symposium of the International Astronomical Union Held in Jaipur, India February 19-23, 2018

The Sun is our nearest star; it is a dynamic star, which changes with time. Solar variations have significant influence on Earth's space environment and climate through the Sun's magnetic field, irradiation and energetic particles. Long-term and reliable historical datasets of solar and stellar activity indices are crucial for understanding the variations and predicting the future solar cycle. IAU Symposium 340 brings together scientists from diverse, interdisciplinary areas to address the latest discoveries from these long-term datasets for the understanding of solar and stellar magnetic cycles. They make comparisons between different datasets and discuss how to make uniform databases. The proceedings of IAU S340 contain a selection of presentations and reviews from internationally renowned experts. They provide an up-to-date account of this field of importance to researchers and advanced students in solar, stellar, space and heliospheric physics.

1. Helio/asteroseismology long-term data: solar/stellar interior velocity fields: status, divergence, and challenges; 2. Long-term magnetic field measurements in the Sun and stars; 3. Sunspot number datasets: Status, divergences, and unification; 4. Solar total irradiance and spectral irradiance long-term data: status, divergences, and challenges; 5. Solar cycle database of solar activity: variations in solar eruptions; 6. Long-term monitoring of stellar activity: lessons for the solar cycle; 7. The variable solar wind and the heliosphere; 8. Solar behavior over centuries using radioisotopes; 9. Physical causes of the solar/stellar cycle irregularities; 10. From past to future: predicting upcoming solar cycle 25.