Recent observations have disclosed how dramatically variable the Sun has been during the last decades. From 1930s until about 2000, the Sun was more active than during the last two thousand years. This period of exceptionally active Sun is now over, and the ongoing solar cycle 24 will remain at the low level of cycles 100 years ago.
Such long-term variations in solar activity are still poorly understood, mainly because the solar polar magnetic fields are measured only since 40 years. Solar polar fields are important for the solar magnetic dynamo and the solar wind, which controls, e.g., the production of energetic particles that can cause significant changes in the Earth's atmosphere and climate.
ReSoLVE studies this exceptional near past of the Sun, especially the variation of polar fields, by reanalysing historic and modern solar and geomagnetic data, developing solar dynamo models and examining effects on the near-Earth environment in a large international collaboration.