Extremely sharp observations indicate that the quasi-periodic pulses are caused by repeated magnetic reconnection – and not by plasma waves as previously thought.
Solar flares are extraordinarily powerful events: magnetic fields become entangled, suddenly released, and release energy and particles. But within this chaos, an interesting phenomenon sometimes appears: the light and radiation rise and fall at a nearly constant rate, like “pulsations” – a phenomenon known as quasi-periodic pulsations (QPP). For years, researchers have debated the origin of this rhythm: Are waves in the plasma dictating the rhythm, or is the rhythm created directly by the energy release process itself?
What is "reconnection" and why is it important?
At the heart of a solar flare is a process called magnetic reconnection: stretched and twisted magnetic field lines are torn and reconnected in a different configuration. Although the description sounds abstract, the meaning is simple: some of the enormous energy stored in the magnetic field is converted into heat, light, and the acceleration of fast particles. Solar flares – as well as flares on other stars – are one of the leading natural laboratories for studying this process.
Observation findings
In a research article published in the journal Nature Astronomy On November 18, 2025, the researchers combined coordinated observations from two key instruments: NASA's IRIS spacecraft/solar telescope, and the one-meter-diameter Swedish Solar Telescope. The key advantage was extraordinary resolution: less than a second in time and about 60 kilometers in space – a true "zoom" on the layers of the solar atmosphere during an eruption.
The researchers measured the downward motion of hot gas in the region of the eruption's "ribbon" (a phenomenon known as chromospheric condensation), and found that these velocities oscillate in a coordinated manner across several layers of the atmosphere, with a period of about 32 seconds. In addition, the oscillations matched changes in hard X-ray radiation—an indication that the energy is arriving in pulses, via precipitation of accelerated electrons into lower layers.
Why do the findings point specifically to "repeated reconnection"?
To explain a “clock” with a period of 32 seconds, the natural candidates are magnetohydrodynamic waves (waves in magnetic plasma). One popular mechanism is the “sausage mode” – a wave that alternately contracts and stretches magnetic structures. But according to the researchers, the data allow us to rule out this explanation as the mechanism that dictates the rhythm. Instead, they argue that the rhythm is due to what is called oscillatory reconnection: the reconnection process itself “opens and closes” in pulses, as does the release of energy and the acceleration of electrons.
On January 7, 2026, it was published in the journal Nature Astronomy Also a News & Views review article, which refines the conclusion for the general public: observations at high space-time resolution indicate that the QPPs are not the product of "sausage" waves, but of repeated reconnection.
The importance of the findings beyond the sun
If quasi-periodic pulses do indeed reflect the "internal rhythm" of magnetic reconnection, they become an important diagnostic tool: These pulses can be used to infer how energy is released not only in the Sun, but also in the eruptions of other stars, and perhaps even in other extreme environments in astrophysics.
The findings are also relevant to space weather research: strong outbursts can affect satellites and communication systems. The better we understand the dynamics of these outbursts, the better we can improve models and predictions.
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