Proba-3 reveals for the first time what is happening in the most hidden part of the Sun’s corona: the “slow” solar wind turns out to be much faster than previously thought
The European Space Agency has published the first scientific results of the Proba-3 mission, and the initial findings have immediately opened one of the more important questions of modern heliophysics: how exactly the solar wind is accelerated in the region where space weather originates, which can later also affect Earth. According to the data ESA presented on 13 April 2026, the Proba-3 satellite pair has already created 57 artificial solar eclipses since July 2025 and collected more than 250 hours of high-resolution images of the Sun’s corona. The first analyses showed that certain structures of the so-called slow solar wind in the inner corona move three to four times faster than scientists had previously expected. This is a result of particular importance because it is precisely in that zone, very close to the Sun’s surface, that the transition takes place between the local dynamics of the magnetic field and the processes that shape the broader space environment throughout the entire Solar System.
The published results do not mean that previous models are necessarily entirely wrong, but they do show that the inner corona is considerably more complex, more dynamic, and less uniform than could be reliably tracked with previous instruments. That is also the main value of Proba-3: the mission does not merely bring another series of beautiful photographs of the Sun, but for the first time enables long-term and very precise observation of a zone that for years had been something of a blind spot in observations. While the solar disk can be observed constantly, and the outer corona has already been monitored for decades by various space coronagraphs, the inner part of the corona remained much harder to access. Yet it is precisely there that it is possible to track the initial acceleration of particles, the formation of plasma jets, and the early phases of processes that can end in geomagnetic disturbances, communication disruptions, and effects on satellites and power systems.
Why the inner corona is so important
The Sun’s corona is the outer, very diffuse, but extremely hot layer of the Sun’s atmosphere. Although the Sun’s visible surface is cooler than the corona, the corona reaches temperatures of more than one million degrees Celsius, which has for decades been one of the major open questions in solar physics. In addition, it is precisely in the corona that the solar wind is formed, a constant flow of charged particles that spreads throughout the Solar System. That wind is neither uniform nor stable: scientists distinguish between fast and slow solar wind, and the slower one is particularly difficult to understand because it is variable, bursty, and associated with smaller structures in the magnetic field.
The problem was that this key transitional region could not be observed often enough or for long enough for a long time. Natural total solar eclipses as seen from Earth provide an extraordinary view of the corona, but they occur rarely and in total last only a few minutes. ESA therefore describes Proba-3 as the first mission that can create an artificial total eclipse in orbit “on demand.” Two satellites, Occulter and Coronagraph, fly in an exceptionally precise formation. One satellite blocks the Sun’s glare like an artificial Moon, while the other simultaneously observes the corona without the blinding light of the solar disk. According to ESA’s data, during those observations the spacecraft operate at a mutual distance of approximately 144 to 150 meters, and the alignment precision is measured in millimeters. This has achieved a technology that had long been regarded as one of the more demanding goals of the European space industry.
It is precisely such a configuration that enabled the ASPIICS instrument to observe the Sun’s corona much closer to the surface than classic space coronagraphs. ESA states that ASPIICS can “see” a region up to about 70,000 kilometers from the Sun’s surface, that is, approximately one tenth of a solar radius above the limb. The abstract of the first scientific paper also states that the instrument observes dynamic processes between 1.3 and 3 solar radii, with a temporal resolution of 30 seconds and a spatial resolution of 5.6 arcseconds. This is not merely a technical detail. In practice, it means that for the first time scientists can build time series dense enough to see how small clumps of plasma accelerate, decelerate, move away from the Sun, or even return toward it.
What the first results showed
The first published results relate in particular to the so-called slow solar wind. Previous expectations were that near the Sun’s surface this wind should have speeds of around 100 kilometers per second. But the team around Andrei Zhukov, head of the ASPIICS instrument at the Royal Observatory of Belgium and lead author of the paper, recorded plasma structures moving in the inner corona at speeds between 250 and 500 kilometers per second. In other words, what had been considered “slow” in that initial region turned out, at least in certain cases, to be much more energetic and faster than expected.
It is important to emphasize that this is not about one isolated event, but about a larger number of small plasma outflows and flows distributed across the instrument’s field of view. According to ESA and the paper abstract, ASPIICS records not only large and striking structures such as coronal mass ejections, but also faint, widespread, and persistent small outflows and inflows of plasma. It is precisely these small signals that suggest why the slow solar wind is so difficult to model. It is not a matter of smooth and orderly flow, but of a mosaic of numerous local processes, miniature changes in magnetic reconnection, and unstable streams that together build the broader picture.
Scientists have long assumed that the slow solar wind forms where magnetic field lines reconnect, separate, and reconnect again. Such processes can eject “bubbles” or clumps of plasma into structures called streamers, bright and elongated rays in the corona. What Proba-3 now shows is that the dynamics within those regions are stronger and more diverse than could be inferred from previous observations. In some cases, the plasma accelerates as it moves away from the Sun; in others, it slows down, and flows directed toward the Sun were also recorded. Such a combination of different directions and accelerations suggests that the inner corona is not merely a place where material “flows outward,” but a region of very complex exchange of energy and motion.
From a natural eclipse lasting a few minutes to an artificial eclipse lasting several hours
A comparison with observations during natural eclipses is perhaps the best way to understand how significant a technological and scientific leap Proba-3 represents. Total solar eclipses on Earth occur on average approximately every 18 months, and totality at a given location lasts only a few minutes. This means that even the most successful observation campaigns are reduced to short, logistically demanding, and meteorologically risky attempts. A single cloud at the wrong moment is enough for months of preparation not to yield a full result.
Proba-3 bypasses that problem in an elegant way. ESA states that the mission can maintain an artificial eclipse for approximately five and a half hours, and earlier mission descriptions highlighted that individual observations can last up to six hours. This gives scientists a completely different type of data: not merely a “frozen” image, but an almost continuous film of changes. If ASPIICS records one to two images per minute, and the scientific paper also mentions observations with a temporal resolution of 30 seconds, sequences are produced from which the movement of plasma through this otherwise inaccessible region can truly be reconstructed.
Such a volume of data also carries symbolic weight. ESA estimates that more than 250 hours of corona imaging is equivalent to observation time that on Earth would require around 5,000 total-eclipse campaigns. Of course, a natural eclipse and a space coronagraph are not identical in all observing conditions, but the comparison clearly shows the scale of the change. What for decades was an occasional opportunity is now becoming a systematic and repeatable measurement.
What this means for space weather and Earth
Although the first results are primarily of interest to solar physicists, the consequences of a better understanding of the inner corona extend far beyond the academic community. The solar wind and coronal mass ejections are the main “drivers” of space weather. When enhanced particles and magnetic structures reach Earth, they can trigger geomagnetic storms, intensify auroras, but also cause technical problems in satellite systems, navigation, radio communications, and power grids. In earlier publications about Proba-3, ESA also recalled the powerful event of May 2024, when the effects of heightened solar activity were visible both in technological systems and in exceptionally pronounced auroras.
That is precisely why it matters whether the “slow” solar wind is accelerating earlier and more strongly than had been assumed. If the initial conditions in the corona are estimated incorrectly, the models that predict the propagation of particles and magnetic structures through interplanetary space may also have limitations. The first Proba-3 results therefore offer not only a new picture of the Sun, but potentially also a new input dataset for improving space weather forecasts. At a time when an enormous part of global communication depends on satellite systems, observing the early phases of solar processes is no longer merely an exotic part of astronomy, but also part of technological security.
It is necessary, however, to keep a sense of proportion. The scientists themselves emphasize that this is the first dataset and that comparison with theoretical models of the magnetic field and plasma acceleration is still to come. In other words, Proba-3 has not yet “solved” the problem of the slow solar wind. But it has shown that the problem can be observed more directly than before and that certain processes in the inner corona do not fully match earlier expectations. That may be the most important mark of a good mission: it does not merely confirm what is known, but opens new questions on the basis of measurements that did not previously exist.
A European mission that has already fulfilled its technological goals
Proba-3 was conceived not only as a scientific project, but also as a technological demonstration. ESA describes it as the first European, but also world-first mission of precision formation flying. The two satellites were launched on 5 December 2024 from the Satish Dhawan Space Centre in Sriharikota, India, aboard a PSLV-XL rocket. The very idea that two separate spacecraft in orbit function almost as a single instrument was demanding in itself, and it was even more demanding to keep the alignment stable enough for one satellite to cast a precise shadow for the other across the optical system.
According to ESA publications, during 2025 Proba-3 achieved several world firsts: first the first precise autonomous formation flying of its kind, and then the first artificial total solar eclipse in orbit. By April 2026, the mission had completed more than 60 extremely precise orbital formation-flying cycles, 57 of which were intended to create artificial eclipses for scientific observations. Thus, at least according to the currently available data, the bulk of the technological goals has already been achieved, so the mission is now moving ever more strongly into the phase of scientific exploitation.
This is important also from a European perspective. Proba-3 shows that highly complex autonomous control operations and coordinated flight can be turned into concrete scientific benefit. In the future, such technology may have broader applications beyond solar physics, from precise space interferometers to future missions that will require extremely stable mutual positioning of multiple spacecraft. In that sense, Proba-3 is not only an instrument for understanding the corona, but also a model example of how a technological demonstration can directly produce top-level science.
ASPIICS is not the only instrument on Proba-3
Although ASPIICS is at the center of attention because of the spectacular images and first results on the solar wind, Proba-3 also carries other useful instruments. DARA, or Digital Absolute Radiometer, continuously measures the Sun’s total energy output with very high precision. Such measurements are important for tracking changes in solar radiation over time and for better understanding solar variability. The third instrument, 3DEES, monitors energetic electrons in Earth’s Van Allen radiation belts, that is, their number, direction of arrival, and energy.
Taken together, that combination shows that Proba-3 serves not only to observe the Sun “from afar,” but also links processes on the Sun with effects in the near-Earth space environment. This is a logical scientific whole: if particle flows and magnetic structures are created on the Sun, and their effects can be measured near Earth in the radiation belts and in broader space weather, a broader picture of cause and effect is obtained. At a time when satellite constellations are becoming more numerous and orbital infrastructure more important, it is precisely such connected measurements that are of particular value.
The biggest work is still ahead
Perhaps the most interesting part of the whole story is the fact that the bulk of the data is still awaiting analysis. ESA emphasizes that a large part of the observations collected so far has not yet been processed and that scientists are being invited to use ASPIICS data to investigate the corona and space-weather processes. This means that the first results are only the beginning, not the final word. In practice, only now is room opening up for more detailed comparisons with numerical models, for checking whether the observed plasma outflows are typical or exceptional, and for more precise separation of the different mechanisms that may accelerate particles.
The open questions remain large and old: what exactly accelerates the solar wind, how the Sun ejects material in coronal mass ejections, and why the corona is so much hotter than the Sun’s surface beneath it. But the difference is that these questions no longer have to be discussed almost exclusively on the basis of indirect indicators and short observing windows. Proba-3 for the first time offers a stable view into the zone in which these processes take place. If the current pace of analysis continues, this mission could in the coming years become one of the key sources of data for understanding the transition between the Sun’s atmosphere and interplanetary space.
For the wider public, the simplest summary is this: Europe created its own solar eclipse in orbit and thereby opened a view into a part of the Sun’s atmosphere that had until now mostly escaped systematic observation. The first result is already strong enough to change expectations about the speed and behavior of the slow solar wind near the Sun. And when the first data from a mission immediately show that reality is more dynamic than the models, that is usually a sign that a very rich scientific period lies ahead.
Sources:- European Space Agency (ESA) – announcement about the first scientific results of the Proba-3 mission and the speed of slow solar-wind structures in the inner corona (link)- European Space Agency (ESA) – official Proba-3 mission page with basic technical data, launch date, and description of formation flying (link)- European Space Agency (ESA) – overview of how Proba-3 fills the observational gap between the solar disk and the outer corona and enables longer observations of an artificial eclipse (link)- European Space Agency (ESA) – announcement about the first artificial total solar eclipse in orbit and the scientific value of the ASPIICS instrument (link)- arXiv / author preprint by Andrei Zhukov and collaborators – abstract of the first ASPIICS instrument results, including observations between 1.3 and 3 solar radii and a temporal resolution of 30 seconds (link)- Crossref – bibliographic record of the paper “Ubiquitous Small-scale Dynamics in the Slow Solar Wind Formation Region Observed by Proba-3/ASPIICS”, confirmation of record version publication on 9 March 2026 (link)
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