Nina Gieseler, Collegium Researcher, Space Research Laboratory
The Sun, humanity’s personal star, is known by all of us. We all have embraced it’s warmth, enjoyed beautiful sunsets, or experienced a sunburn. Like everybody might have their own perspective on the Sun, my personal relationship is a particular one. While I really enjoy sunbathing I see the Sun also as a kind of employer. The Sun produces what I study: energetic particles, accelerated to high energies in solar eruptions.
I am, therefore, very familiar with the Sun’s rough side, its dangerous aspects, its ugly face. I imagine the Sun as a dragon. Right now it is a sleepy dragon, just about to fully wake up. That might sound a bit scary, and yes, it is! While the Sun never stops to shine, this other kind of radiation, the energetic particle radiation, occurs sporadically, and if it hits Earth, it can harm all life! We call this space weather, and when these solar storms blow, you better get inside if you are an astronaut; you better power off if you are a satellite. And you better don’t fly with a plane over the poles, where the Earth’s magnetic field can’t significantly shield you.
The last deep-sleep phase was in 2019/2020, characterized by the dragon not changing its appearance, nothing happening, boring even. This is called solar minimum. We know this phase but we also know what comes after! The question is, “when will it happen and how bad will it be?”
We know that the Sun’s sleep-wake cycle (the solar activity cycle) is 11 years long. Right now it begins to blink: little sun spots appear and disappear here and there on the dragon’s skin (that is, the visible surface of the Sun, called photosphere). But we don’t know enough about this beast yet to fully understand and foresee its anger.
But humans haven’t been lazy while the dragon was sleeping: We built spacecraft and instruments, tested and developed, and finally sent these up to interplanetary space. These little explorers are packed with sensors and cameras, armed with heat shields, and are well prepared to stand the fight with the angry dragon. ‘The fight’ is to study the monster, try to predict when it will attack again.
Some space probes were already there during the last solar activity maximum, some veterans even before. But now there are some new kids on the block: ESA’s Solar Orbiter, NASA’s Parker Solar Probe, and the ESA/JAXA mission BepiColombo.
Altogether, they are orbiting the dragon, sneaking around it, and forming an unprecedented spacecraft fleet. They are there to join forces; to watch the dragons front and back at the same time, to watch from close and far distances when it spits fire.
This is what my research is about. I am analyzing combined observations of these energetic particle events taken by all these little brave adventurers to understand how the dragon produces its fire (how the particles are accelerated) and how the dragon throws its fire at us (how the particles are transported through interplanetary space). The new space missions have heralded a new era in my research field, and it is really exciting to make use of these new opportunities offered by our new space fleet! My whole research community seems to be pushed right now: our collaborations become more lively and international. But maybe the pandemy plays a role here as well. We finally learned how to really make use of video conferencing and found that meeting a colleague from the US is not so much different than meeting someone from Turku if you are at the home office.
Energetic proton observations by UTU’s particle detector ERNE onboard the SOHO spacecraft. The peaks mark solar energetic particle events and illustrate the solar activity cycle as a function of time. (Adapted from https://omniweb.gsfc.nasa.gov/ftpbrowser/soho_erne_flux_hr.html)
The black spikes in the figure mark the dragon’s fire activity of the last 20 years (energetic proton events). The recent dragon’s wake-up phase is different to the previous one. It is stronger, faster, and the brave explorers were already challenged by the first large outbreaks, sending energetic particles to nearly all directions.
What may appear threatening is, of course, big fun for the scientists and spacecraft teams waiting to test the new equipment. The Sun gives us work to do and proves its importance. We are eagerly waiting for more, for stronger events that can even be measured on Earth’s ground, and for wider events seen by every observer out there. We are ready for the dragon’s next rage!
