I will present a study of solar activity on the long and very long term. I will first present different solar activity indicators available and their timelines. I will then focus only on a few long term indices to understand the different patterns present in solar activity (periodicities on different timescales, long term variations). As the Sunspot Number is the longest direct measurement of solar activity, we will focus on this well-known index and its historical origins, construction and re-construction that might influence its long term variations. We will also explain how it is built on a day-to-day basis here at SILSO. To conclude, we will see what the Sunspot Number series is used for and how we can use it to predict future solar activity.
This seminar is the third of a series of seminars on the basics of solar and heliospheric physics, aimed at our ROB, IASB and RMI colleagues who have a sound knowledge of physics and mathematics but never had a formal education in solar and heliospheric physics. These talks will provide an overview of the most important aspects without going in too much detail. References for further reading are provided.