The Solar acts because the Photo voltaic System’s final particle accelerator, hurling out streams of high-speed electrons.
Because of ESA’s Photo voltaic Orbiter, scientists have traced these energetic electrons again to their photo voltaic origins, revealing two distinct sorts: sudden bursts from photo voltaic flares and extended waves from huge eruptions referred to as coronal mass ejections (CMEs).
Photo voltaic-Powered Particle Accelerator
The Solar acts because the Photo voltaic System’s final particle accelerator. It pushes electrons to speeds approaching that of sunshine, hurling them into house and filling the Photo voltaic System with what scientists name ‘Photo voltaic Energetic Electrons’ (SEEs).
Utilizing ESA’s Photo voltaic Orbiter spacecraft, researchers have now tracked these high-energy electrons again to their origin on the Solar. The outcomes present that there are two distinct sorts of SEE occasions. One is linked to highly effective photo voltaic flares (eruptions from smaller, lively areas on the Solar’s floor), whereas the opposite comes from huge outbursts of scorching plasma in the Sun’s atmosphere (called ‘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.
A Clearer Connection
Scientists had long suspected that two categories of SEE events existed, but Solar Orbiter’s unique vantage point made it possible to confirm this in detail. The spacecraft observed far closer to the Sun than earlier missions and captured an unusually large set of events, allowing researchers to see how the electrons formed and escaped.
“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.”
The EUI footage (yellow) shows million-degree gas in the Sun’s atmosphere. A narrow ejection of gas from the flare called a solar jet, can be clearly seen heading towards the bottom right of the inset.
Solar flares release electrons both outwards into space and inwards towards the Sun’s surface. When they hit the Sun’s surface, they generate X-rays. This X-ray emission, recorded by STIX, is overlaid in blue.
Credit: ESA & NASA/Solar Orbiter/EUI & STIX
Largest SEE Study Yet
The study is the most comprehensive of SEE events to date, and produces a catalogue that will only grow through Solar Orbiter’s lifetime. It used eight of Solar Orbiter’s ten instruments to observe more than 300 events between November 2020 and December 2022.
“It’s the first time we’ve clearly seen this connection between energetic electrons in space and their source events taking place at the Sun,” adds co-author Frederic Schuller, also of AIP.
“We measured the particles in situ – that is, Solar Orbiter actually flew through the electron streams – using the probe’s Energetic Particle Detector, while simultaneously using more of the spacecraft’s instruments to observe what was happening at the Sun. We also gathered information about the space environment between the Sun and spacecraft.”
The Metis instrument images the Sun’s outer atmosphere by artificially covering its bright disc, similar to what happens during a total solar eclipse. In this movie, the Sun’s size and position are depicted by the white circle.
Credit: ESA & NASA/Solar Orbiter/Metis
Flight Delays in Space
The researchers detected the SEE events at different distances from the Sun. This let them study how the electrons behave as they travel through the Solar System, answering a lingering question about these energetic particles.
When we spot a flare or a CME, there’s often an apparent lag between what we see taking place at the Sun, and the release of energetic electrons into space. In extreme cases, the particles seem to take hours to escape. Why?
“It turns out that this is at least partly related to how the electrons travel through space – it could be a lag in release, but also a lag in detection,” says co-author and ESA Research Fellow Laura Rodríguez-García. “The electrons encounter turbulence, get scattered in different directions, and so on, so we don’t spot them immediately. These effects build up as you move further from the Sun.”
Turbulence in Solar Space
The space between the Sun and the planets of the Solar System isn’t empty. A wind of charged particles constantly streams out from the Sun, dragging the Sun’s magnetic field with it. It fills space and influences how the energetic electrons travel; rather than being able to go where they like, they are confined, scattered, and disturbed by this wind and its magnetism.
The study fulfills an important goal of the Solar Orbiter: to continuously monitor our star and its surroundings, tracing ejected particles back to their sources at the Sun.
“Thanks to Solar Orbiter, we’re getting to know our star better than ever,” says Daniel Müller, ESA Project Scientist for Solar Orbiter. “During its first five years in space, Solar Orbiter has observed a wealth of Solar Energetic Electron events. As a result, we’ve been able to perform detailed analyses and assemble a unique database for the worldwide community to explore.”
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.
“Knowledge such as this from Solar Orbiter will help protect other spacecraft in the future, by letting us better understand the energetic particles from the Sun that threaten our astronauts and satellites,” adds Daniel. “The research is a really great example of the power of collaboration – it was only possible due to the combined expertise and teamwork of European scientists, instrument teams from across ESA Member States, and colleagues from the US.”
Vigil and the Next Frontier
Looking ahead, ESA’s Vigil mission will pioneer a revolutionary approach, operationally observing the ‘side’ of the Sun for the first time, unlocking continuous insights into solar activity. To be launched in 2031, Vigil will detect potentially hazardous solar events before they come into view as seen from Earth, giving us advance knowledge of their speed, direction and chance of impact.
Our understanding of how our planet responds to solar storms will also be investigated further with the launch of ESA’s Smile mission next year. Smile will study how Earth endures the relentless ‘wind’, and sporadic bursts, of fierce particles thrown our way from the Sun, exploring how the particles interact with our planet’s protective magnetic field.
Reference: “CoSEE-Cat: A Comprehensive Solar Energetic Electron event Catalogue obtained from combined in situ and remote-sensing observations from Solar Orbiter – Catalogue description and first statistical results” by A. Warmuth, F. Schuller, R. Gómez-Herrero, I. Cernuda, F. Carcaboso, G. M. Mason, N. Dresing, D. Pacheco, L. Rodríguez-García, M. Jarry, M. Kretzschmar, K. Barczynski, D. Shukhobodskaia, L. Rodriguez, S. Tan, D. Paipa-Leon, N. Vilmer, A. P. Rouillard, C. Sasso, S. Giordano, G. Russano, C. Grimani, F. Landini, C. Mac Cormack, J. A. J. Mitchell, A. Fedeli, L. Vuorinen, D. Lario, H. A. S. Reid, F. Effenberger, S. Musset, K. Riebe, A. Galkin, K. Makan, S. Reusch, A. Vecchio, O. Dudnik, S. Krucker, M. Maksimovic, J. Rodríguez-Pacheco, M. Romoli and R. F. Wimmer-Schweingruber, 32 August 2025, Astronomy & Astrophysics.
DOI: 10.1051/0004-6361/202554830
Solar Orbiter is a space mission of international collaboration between ESA and NASA, operated by ESA.
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