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Double trouble: Solar Orbiter traces superfast electrons back to Sun

The European Space Agency-led Solar Orbiter mission has split the flood of energetic particles flung out into space from the Sun into two groups, tracing each back to a different kind of outburst from our star. Antonio Vecchio of Radboud University was part of the research team. The space craft Solar Orbitor flew directly through the electron stream.

The Sun is the most energetic particle accelerator in the Solar System. It whips up electrons to nearly the speed of light and flings them out into space, flooding the Solar System with so-called ‘Solar Energetic Electrons’ (SEEs).

Researchers have now used Solar Orbiter to pinpoint the source of these energetic electrons and trace what we see out in space back to what’s actually happening on the Sun. They find two kinds of SEE with clearly distinct stories: one connected to intense solar flares (explosions from smaller patches of the Sun’s surface), and one to larger eruptions of hot gas from the Sun’s atmosphere (known as ‘coronal mass ejections’, or CMEs).

‘We see a clear split between ‘impulsive’ particle events, where these energetic electrons speed off the Sun’s surface in bursts via solar flares, and ‘gradual’ ones associated with more extended CMEs, which release a broader swell of particles over longer periods of time’, says lead author Alexander Warmuth of the Leibniz Institute for Astrophysics Potsdam (AIP), Germany.

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A clearer connection

While scientists were aware that two types of SEE event existed, Solar Orbiter was able to measure a large number of events, and look far closer to the Sun than other missions had, to reveal how they form and leave the surface of our star.

‘We were only able to identify and understand these two groups by observing hundreds of events at different distances from the Sun with multiple instruments – something that only Solar Orbiter can do’, adds Alexander. ‘By going so close to our star, we could measure the particles in a ‘pristine’ early state and thus accurately determine the time and place they started at the Sun.’

Keeping Earth safe

Crucially, the finding is important for our understanding of space weather, where accurate forecasting is essential to keep our spacecraft operational and safe. One of the two kinds of SEE events is more important for space weather: that connected to CMEs, which tend to hold more high-energy particles and so threaten far more damage. Because of this, being able to distinguish between the two types of energetic electrons is hugely relevant for our forecasting.

Antonio Vecchio of Radboud Radio Lab is very happy with this research: ‘This work represents the paradigm of the Solar Orbiter mission: a multi-instrumental mission developed to simultaneously study the different manifestations of the solar magnetic activity. It was very interesting to collaborate, discuss, and argue with people from different fields with different mindsets and different approaches to the analysis. Putting our skills together and learning from  the different methodologies of colleagues allowed us to achieve this result.’

Read more from ESA.

Contact information

For further information, please contact the researcher involved or team Science communication via +31 24 361 6000 or media [at] ru.nl (media[at]ru[dot]nl).   

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