Researchers from the California Institute of Technology have built a model of a plasma loop in the laboratory,
To carry out the analysis, physicists built a vacuumchamber with double electrodes inside. They charged a capacitor and then ran the energy through electrodes to create a miniature loop of the sun's corona. The whole process was recorded on a camera that takes 10 million pictures per second. Each cycle lasted about 10 μs and led to the formation of a loop 20 cm long and about 1 cm in diameter. Although it is much smaller than the solar one, the structure is identical to the real one.
Similarities between real (top) and laboratory (bottom) solar flares. Image: Bellan Lab, Caltech
The study showed that the loops of the solar coronaare not a single structure, but rather fractally woven threads, similar to a large rope. “If you cut a piece of rope, you will see that it consists of weaves of individual threads. Separate these individual strands and you will see that they are braids of even finer strands, and so on. Plasma loops work in exactly the same way,” says Yang Zhang, co-author of the study.
Scientists have found that such a structure is important forgeneration of high-energy particles and X-rays during a solar flare. Plasma is a strong electrical conductor. But when too much current tries to pass through the solar corona loop, the structure undergoes a change. A bend is formed in the loop - instability in the form of a corkscrew, as a result, individual threads begin to break. In this case, each thread relieves the load on the remaining ones.
Laboratory simulation of a solar flare. Image: Bellan Lab, Caltech
Studying the process microsecond by microsecond,the scientists noticed the spike in negative voltage associated with the burst of X-rays just as the filament broke. This change in voltage is similar to the pressure drop that occurs at the narrowing of a water pipe. The electric field from this voltage spike accelerates the charged particles to extreme energies, and then as they slow down, X-rays are emitted.
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On the cover: a simulation of a plasma loop on the surface of the Sun. Image: Bellan Lab, Caltech