Solar Orbiter recorded a second before the flash: how the M-class solar flare “unraveled” on September 30, 2024
Footage created just a second before a powerful M-class solar flare, which erupted from the surface of the Sun on September 30, 2024, opened a rarely clear window into the moment when accumulated magnetic energy turns into an explosion of radiation and accelerated plasma. The scene was captured by the Solar Orbiter mission, led by the European Space Agency (ESA), with a level of detail that previously could not be obtained in space simultaneously in space and time. Instead of a “frozen” frame, scientists obtained a temporally densely sampled sequence of events showing how the flare is born from previously weak disturbances, and then in a short time grows into a violent release of energy.
The video is composed of images from the Extreme Ultraviolet Imager (EUI) instrument, recorded every two seconds leading up to the flare. Such a rhythm, along with high resolution, made it possible to recognize tiny “sparks” along the filament structure, specifically places of magnetic reconnection – a process in which magnetic field lines break and reconnect, releasing a large amount of energy. The sequence also brought concrete numbers: speeds of the filament “unraveling” in hundreds of kilometers per second and the moment when one end of the structure detaches and “flies out” into space.
The filament as twisted magnetic “rope”: what is seen before the eruption
The central element of the scene is a dark filament, relatively cooler and denser plasma that can “hang” in the solar corona along magnetic lines, so it appears darker than the surroundings in the extreme ultraviolet spectrum. Filaments often take the form of long ribbons or “ropes” connecting areas of different magnetic polarity on the surface. Their survival depends on a delicate balance between gravity, plasma pressure, and magnetic forces. When that balance is disturbed, the filament can erupt, and in many cases, this is associated with the appearance of a solar flare and, sometimes, with a coronal mass ejection into interplanetary space.
In the event of September 30, 2024, it is seen how the filament begins to rise above the surface, and then unravels like a rope under tension. One end remains connected to the Sun, while the other gradually breaks free and finally detaches. Analysis of changes through successive frames showed that the “unraveling” along the part that remained connected took place at a speed of about 250 kilometers per second. Towards the place where the filament detached, speeds increased and reached approximately 400 kilometers per second. at the moment of the break, part of the filament was launched towards space, while the remaining part stayed tied to the Sun and continued to reshape itself.
These numbers are not just impressive; they are a measure of how quickly the corona can “respond” to a change in magnetic topology. Accelerations of plasma to hundreds of kilometers per second point to a sudden redistribution of energy in the magnetic field. Precisely such transitions – from slow, almost imperceptible motion to a very fast phase – form the core of the question scientists are trying to solve: what exactly is the trigger that turns a calm filament into an eruption and a flare.
Sparks along the filament and reconnection: where the “excess” energy arises
In the frame, numerous tiny, very bright flashes are seen along the filament, arranged like a series of sparks. Expert interpretation links them to places of magnetic reconnection – points where twisted magnetic field lines separate and reconnect in a new arrangement. Reconnection is one of the fundamental mechanisms of energy release in plasma: it allows magnetic energy to be converted into heat, radiation, and kinetic energy of material. In practice, this means that part of the plasma suddenly heats up to millions of degrees, while particles and material nearby accelerate and change directions of motion.
What is particularly important about this sequence is the impression that the flare does not necessarily begin with a “big bang”. Instead, the event develops from a series of initially weak disturbances that quickly intensify. Scientists compared this pattern to avalanches: the movement of a small amount of snow can be a trigger, but then the system cascades and grows into a much larger collapse. On the Sun, this means that local changes in the magnetic field, which in different conditions might remain without consequences, can spark a chain reaction of reconnection and destabilization of a larger area.
Precisely for this reason, the combination of high spatial and temporal resolution is crucial. If “tiny” events are seen clearly, it is possible to more reliably link micro-processes with macro-consequences, such as the detachment of a filament or the development of the flare’s light maximum. In slower instruments, such phases would merge into one, so cause and effect would be harder to separate. Here, however, it is seen how the “tension” of the system is released through multiple tiny cracks before the main release occurs.
Plasma “rain” after the flare: the event does not end when the light calms down
The sequence does not end with the peak of the flare. On the contrary, high resolution reveals a scene that is equally scientifically interesting: a “sky” filled with plasma clumps that continue to fall towards the Sun after the eruption. These are droplet-like “blobs” of plasma that, after being lifted and heated, cool down and return along magnetic lines. This creates an effect resembling rain, which is often associated in literature with coronal rain and thermal instabilities in the corona.
For plasma physics, this detail is important because it shows that energy distribution is not a one-time event. After reconnection, part of the plasma remains in a hot state, part condenses and becomes denser, and part returns towards the lower layers of the atmosphere. Such “post-flare” dynamics speak to how the corona manages heat and mass and how long the return to a calmer state can take. At the same time, it reminds us that the consequences of a flare are not measured only by the intensity of radiation in the minute of the peak, but also by changes in the structure and movement of material that continue to shape the corona.
How the video was created: EUI, JHelioviewer, and processing in Belgium
EUI is an instrument designed to image structures in the solar atmosphere from the chromosphere to the corona, with an emphasis on high resolution and the ability for rapid imaging. In this case, frames were recorded every two seconds, which enabled the creation of a film in which fine changes can be tracked without large time “gaps”. The animation shown to the public is sped up for clarity, while the actual flare lasted about fifteen minutes. But the key moments of destabilization and filament breakage took place on very short scales, precisely those on which continuous insight is usually hardest to obtain.
The visualization was created by a group of scientists from the Royal Observatory of Belgium, using JHelioviewer – software that allows the stacking and analysis of solar sequences from different instruments and missions. Thereby, along with the scientific result, an example was created of how data can be brought closer to a wider audience without losing key information. The video also showed that top-tier scientific content can be shared in a format understandable to those who are not specialists, while retaining a serious interpretation of the background processes.
M-class flare and possible consequences: radio blackouts and sensitivity of the polar region
In the classification of solar flares (A, B, C, M, X), the M-class is located below the most powerful X-flares, but can still cause measurable effects on Earth. The most common immediate effect are short-term radio blackouts, especially at high geographical latitudes, where changes in the ionosphere more strongly affect the propagation of radio waves. NOAA’s space weather scale for radio blackouts (R1 to R5) links such effects to the peak power of the flare in soft X-ray wavelengths. In practice, M-class often means that short interruptions or degradations of communication are possible, primarily in specific zones and conditions.
It is important, however, to distinguish a flare from other forms of solar activity. The greatest risk for geomagnetic storms, which can create challenges for satellites and power grid systems, usually comes from coronal mass ejections (CME) and whether the ejection is directed towards Earth and what its magnetic orientation is. An M-class flare can pass almost without consequences if there is no Earth-directed CME or if the ejection is directed in another direction. But even then, the message is clear: the magnetic system on the Sun was tense enough to produce an eruptive event, which increases interest in surrounding active regions and their further development.
Context 2024: solar maximum of cycle 25 and increased probability of eruptions
The event of September 30, 2024, fits into a period of heightened Solar activity. NASA and NOAA announced in October 2024 that the Sun entered the period of solar maximum of Solar Cycle 25, which means a statistically higher number of spots, eruptions, and flares. In the cycle maximum, it is not necessary that all events are extreme, but the “background” is more active, and the probability of the occurrence of M- and X-class flares is higher than in the minimum. For missions observing the Sun, this period is extremely valuable, because a large number of examples of different eruptions can be collected in a relatively short time and their common features compared.
In a practical sense, the solar maximum is also a period of increased need for operational warnings. Satellite communications, navigation, and ionosphere monitoring have become part of infrastructure, and part of aviation routes pass over areas where radio links are more sensitive. A higher frequency of events also means more opportunities to test early warning systems and risk assessments. At the same time, this is a period when the public more often notices consequences in the form of intensified auroras, although the same physical phenomena that create the “light spectacle” can also create technical challenges.
Why Solar Orbiter is important: proximity to the Sun and connecting cause and effect
Solar Orbiter is an international mission of ESA and NASA, launched in 2020, designed to observe the Sun from the inner part of the Solar System. Its orbit gradually brings it to approximately 0.28 astronomical units, which allows a sharper view of fine structures in the corona than from the distance of Earth’s orbit. Additionally, as the mission progresses, the inclination of the orbit increases, opening up better views of high heliographic latitudes and polar regions – key for understanding the global magnetic field and the development of solar cycles.
The advantage of Solar Orbiter is not only in proximity, but also in the combination of instruments. Remote sensing instruments, like EUI, display the “scene” in the Sun’s atmosphere, while in situ instruments measure particles, magnetic fields, and solar wind at the spacecraft itself. This creates the possibility to link solar events with what later travels through the heliosphere and, depending on direction, can reach Earth. Such linking is important for “connection science”, i.e., understanding how Solar activity shapes conditions in interplanetary space.
In the case of the flare of September 30, 2024, EUI showed how important it is to observe a flare as a process, and not just as a moment of maximum. The second before the eruption becomes scientific information because it suggests that there are measurable signals of destabilization. If such signals are recognized in more examples, they can become part of more realistic risk assessments and earlier warnings, even though space weather forecasting is not yet at the level of precision of meteorological forecasting on Earth.
What scientists get from such “movies”: measurements, models, and a better description of triggers
The greatest value of such a sequence lies in the fact that it enables quantitative analysis. From a series of frames, plasma movement speeds, changes in the geometry of magnetic structures, and the arrangement of reconnection sites can be measured. These are input data for computer models attempting to describe how instabilities arise and how they develop. When data are sparse, models rely on assumptions and averages; when data are dense, models can be directly verified and improved.
Such results also shift the debate about the “trigger”. If it is shown that certain types of weak disturbances regularly precede filament detachments or flare development, that is a step towards earlier recognition of risks in active regions. If it is established that reconnection often “travels” along the filament before the main break, this helps understand how energy is distributed in space. In other words, the film is not just an illustration, but a laboratory at a distance – an experiment taking place on the Sun, but which can be analyzed on Earth with measurable parameters.
At the same time, the story about the avalanche reminds us that the system is nonlinear: a small cause can lead to a large consequence, but only if the conditions are “ripe”. That is precisely why it is important to observe “quiet” phases as well, and not just large peaks. The Solar Orbiter sequence shows that these quiet moments are full of information, they just need to be recorded fast enough and clearly enough.
The Sun as an infrastructural factor: why constant monitoring becomes a necessity
Space weather is no longer a side topic for enthusiasts, but a factor entering into risk assessments for communications, navigation, and satellite systems. Short radio blackouts can be a problem for specific sectors, and changes in the ionosphere can affect precise positioning. Larger geomagnetic storms are rarer, but are taken seriously in infrastructure planning precisely because they can have wider consequences. In such an environment, observing the Sun becomes part of a preventive approach: the more is known about triggers and the early phase of events, the more realistically protection and response protocols can be set.
The footage of the “second before” the M-class flare of September 30, 2024, shows how a large eruption is born from a series of tiny changes that until yesterday were out of reach for most instruments. In it, it is seen that the Solar corona is not a static background, but a dynamic field in which magnetic structures rearrange, break, and reconnect from second to second. Precisely such frames – clear, fast, and measurable – make the difference between a fascinating image and an understanding of a process that, ultimately, can affect life on Earth as well, although it takes place 150 million kilometers away.
Sources:- European Space Agency (ESA) – video and description of the Solar Orbiter M-class flare of September 30, 2024 (link)- NOAA Space Weather Prediction Center – explanation of solar flares and radio blackouts (R-scale) (link)- NASA Goddard Scientific Visualization Studio – NASA and NOAA announcement on solar maximum of cycle 25 (October 15, 2024) (link)- SIDC / Royal Observatory of Belgium – introduction and description of the EUI instrument on Solar Orbiter (link)- Max Planck Institute for Solar System Research – overview of the EUI instrument and its telescopes (link)
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