Solar Orbiter findings point to a "domino" model of renewed magnetic fusion that rapidly escalates into a high-intensity eruption
Solar flares are among the most energetic phenomena in the solar system. Within a few minutes, enormous amounts of energy accumulated in complex magnetic formations in the solar corona are released. While the scientific community has identified the process of magnetic reconnection as the fundamental mechanism for decades, a fundamental question remains unanswered: how exactly does the energy release occur at such a rapid rate, and under what conditions does a high-power flare develop instead of a sequence of minor events. Recent findings from the Solar Orbiter spacecraft raise a concrete suggestion: the mechanism is not based on a single "explosion", but on a graduated sequence of small-scale reconnection events, which quickly escalate to create a "magnetic avalanche" that drives the main flare.
Research and observation method
The data were obtained during an event recorded during a close pass of the Solar Orbiter spacecraft relative to the Sun, on September 30, 2024. The observation teams managed to carry out an extraordinary coordination of different instruments, allowing continuous monitoring from the hot coronal layers to the photosphere region. The main innovation lies in the combination of several measurement instruments, with a major contribution being received from the EUI (Extreme Ultraviolet Imager), which provided a sequence of images with extremely high spatial resolution and a rapid sampling rate (updates approximately every two seconds). This made it possible to monitor the fine dynamic details of the event. At the same time, complementary data were collected regarding temperatures, the structure of the magnetic field, and energetic emissions such as X-ray radiation, in order to avoid drawing conclusions based on a single observation source.
The concept of "magnetic avalanche" – a physical explanation
The appropriate analogy is that of an avalanche: a small initial change triggers further changes, which in turn trigger the next event, thus creating a chain reaction that spreads in time and space. According to the description in the study, in the early stages of the event, small and temporary areas of magnetic reconnection occur in the corona. These processes change the local configuration of the magnetic field or weaken its stability, thereby creating favorable conditions for further magnetic reconnection to occur in nearby areas, and so on. Rather than perceiving the eruption as a single monolithic event, the resulting picture is of a system of tiny events that feed into each other until a critical threshold is reached at which an eruption of considerable power is created.
Observation of "coronal rain" after the peak of the eruption
One of the interesting signatures in the observations is the appearance of "coronal rain": luminous plasma blobs that appear to "fall" along the arcs of the magnetic field even after the central eruption has faded. This phenomenon is important because it indicates that the system continues to undergo energetic processing and reorganization of the magnetic fields even after the peak, and does not immediately return to a state of equilibrium. If the avalanche mechanism is indeed a common phenomenon, it is possible that signatures of this type could be used in the future as an indicator that the active region still has the potential to release additional energy.
Implications for space weather forecasting
High-intensity eruptions can lead to a cascade of effects that reach Earth, such as geomagnetic storms, disruptions to radio communications, and increased exposure of satellites to radiation. The current study does not offer immediate prediction of large eruptions, but it does provide a detailed physical model for which we can look for “early warning signs” – for example, the frequency and intensity of small-scale magnetic reconnection events that occur before a major eruption. The scientific assumption is that if capabilities are developed to identify escalation patterns, early warning systems can be improved.
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