Sun simulations reveal how cool prominences survive in million-degree corona
Introduction
At more than one million degrees, the sun's atmosphere—the corona—is incredibly hot; but not everywhere. Time and again, huge structures of significantly cooler solar plasma—about 10,000 degrees—appear within the corona. These structures are known as prominences. They span up to several thousand kilometers and often resemble flickering flames that can take on a wide variety of shapes. Despite their delicate appearance, they are massive "chunks of matter": their density exceeds that of the surrounding corona by more than a hundred.
"Our calculations show, more realistically than ever before, how both processes interact to supply the prominences with material and thus keep them alive." – Lisa-Marie Zessner-Ondratschek
Understanding Solar Prominences
In a sense, it is as if a giant mountain were suspended in mid-air. Prominences can remain stable for weeks or even months, yet they also possess explosive potential: if they do not fade away quietly, they culminate in a massive eruption during which the sun hurls charged particles into space. If the particle cloud spreads toward Earth, it can trigger violent solar storms.
Research Overview
In a study appearing in Nature Astronomy, researchers at the Max Planck Institute for Solar System Research (MPS) in Germany investigate how prominences form and what the secret of their longevity is. Their findings reveal that multiple processes are at work, creating a constant balance between material loss and supply.
| Aspect | Description |
|---|---|
| Temperature Contrast | The corona is around 1,000,000 degrees Celsius, while prominences are about 10,000 degrees. |
| Density | Prominences have a density over a hundred times greater than the corona. |
| Formation Duration | Prominences can last for several days to weeks, depending on various factors. |
| Explosive Potential | When destabilized, they can erupt, sending particles towards Earth. |
Simulation Techniques
In complex computer simulations, the researchers model the interaction of magnetic fields and plasma within the sun. They consider not only the sun's atmosphere, where the prominences manifest but also the deeper, cooler layers of our star. These layers, beneath the sun's visible surface, generate the sun's complex, constantly changing magnetic field, which extends into the corona.
The new computer simulations are based on a magnetic field structure that is often associated with prominences.
Key Mechanisms Behind Prominence Stability
Research suggests that the magnetic field is a significant driving force in the formation and maintenance of prominences. Specifically, the temperature gradient within these layers plays a critical role. The maximum temperature of 20,000 degrees in the chromosphere is significantly cooler than the corona, which introduces essential dynamics for prominence formation.
Conclusion
In conclusion, solar prominences are a fascinating aspect of solar physics and their understanding is crucial not only for solar research but also for predicting space weather effects on Earth.
