It is now 50 years since Neil Armstrong set foot upon the moon. NASA, and several private space companies, have active plans to return astronauts there soon, with the goal of establishing a longer-lasting presence. These missions, and other future missions into deep space, will need to worry about exposure of the astronauts to damaging radiation from space weather, which has its origins in emissions from the Sun.
The Sun is in many respects a Rosetta stone for astrophysics, since we have the ability to study it up-close in ways not yet possible for other stars. Our observations are providing crucial insights on its past and future. There is direct relevance in these studies for us here on Earth because the Sun has an impact on the terrestrial environment through its changing outputs and emissions, its activity, which gives rise to space weather.
The Sun produces emissions of highly charged particles in its solar wind and through vast, energetic events called coronal mass ejections. Some of these emissions travel towards the Earth, where they interact with the Earth’s magnetic field. These interactions give rise to the beautiful spectacles of the northern and southern lights, the aurora borealis and aurora australis. However, they also affect global communications and damage satellites, and extreme events can damage power grids. Exposure in space to this ionizing radiation can be very damaging to biological tissue.
The Sun’s emissions also vary on different timescales, the most conspicuous being an 11-year cycle of activity. One cycle is not the same in strength as another. The most recent cycle, which is just ending, has been the weakest for 100 years.
Space weather and risks from it now feature on the government’s National Risk Register. The challenge is to be able to understand what drives the Sun’s emissions and their variability, and to predict space weather, in particular the occurrence of extreme events: in short, to perform space-weather forecasting. Activity, emissions and space weather all have their origins in processes taking place inside the Sun, where complex patterns of rotation help to shape and evolve the star’s magnetic fields, which then erupt through the surface leading to these energetic events. We have an unprecedented window on these internal processes thanks to our global network of automated solar telescopes, the Birmingham Solar-Oscillations Network (BiSON) . BiSON has been monitoring the Sun’s global oscillations for more than 30 years. These oscillations provide a probe of the otherwise hidden interior. Using these “helioseismology” data, we discovered structural changes that took place in the lead up to the most recent cycle, which with the benefit of hindsight suggested the Sun’s activity would weaken. Will the next cycle be the same?
The current and future data that BiSON and other solar telescopes and satellites collect are especially crucial as we seek to understand better the Sun’s cyclic behaviour. We are also investigating whether cosmic ray detectors from the HiSPARC network may be sensitive to space-weather events. Local schools host some of the detectors. With many spread around Europe there is the potential to use them in space-weather forecasting, and interest from the Met Office.
Finally, there are wider implications, beyond the Sun and the Earth: What about other stars, their activity, and impact and the planets they may host? How typical a star is the Sun, and how many other solar systems like our own are there out there?