Although it may look like a static ball of fire in the sky from our perspective, the Sun is very active and produces solar flares that can impact our planet. The strongest of these flares have the capacity to cause blackouts and disrupt communications on a global scale.
While solar flares are powerful by themselves, they are nothing compared to thousands of “superflares” that are observed by NASA’s Kepler and TESS missions. These superflares are produced by stars that are 100 to 10,000 times brighter than the Sun.
The physics is believed to be the same between the solar flares on our sun and the superflares on other planets — they are sudden releases of magnetic energy, But since the super-flaring stars have stronger magnetic fields, they have brighter flares. But the superflares have some unusual behaviorus— they have in initial short-lived enhancement followed by a secondary longer-duration but less intense flare.
Scientists developed a model to explain the phenomenon, which was published in a paper in The Astrophysical Journal on Wednesday.
It was thought that the visible light in these flares only came from the lower layers of a star’s atmosphere. Particles that are energised by “magnetic reconnection” fall down from the hot corona (outer layer of the star) and heat these layers. But recent work put forward the hypothesis that the emission from coronal loops may also be detected for super-flaring stars but that their density in these loops would need to be extremely high for that.
Unfortunately, there was no real way to test this since we cannot really see those loops—hot plasma trapped by a star’s magnetic field—on stars other than our Sun. But other astronomers who were not part of the study spotted stars that had a peculiar light curve which was similar to a celestial “peak-bump,” or a jump in brightness. As it turned out, this light curve bore a resemblance to a solar phenomenon where a second more gradual peak follows the initial burst. It reminded the astronomers of a phenomenon on the Sun called late-phase flares.
This prompted the question — could the same process produce similar late-phase brightness in visible light? The researchers answered that by adapting fluid simulations that had been frequently used to simulate solar flare loops and scaled up the loop length and magnetic energy. They found that the large flare energy input pumps a lot of mass into the loops. This resulted in dense, bright visible light emissions.
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First published on: 08-12-2023 at 15:34 IST
