Tiny solar flares may be heating up the Sun’s corona


Origin of coronal X-ray emissions could be key to answering a question that has long baffled scientists.

Tiny solar flares previously undetectable from Earth may be heating up the Sun’s corona or outer atmosphere, and might be responsible for it being hotter than the Sun’s surface, according to a new study by an international group of scientists from the US, Switzerland, and Japan.

Scientists have long been puzzled as to why the corona is so much hotter than the Sun’s surface. They have been unable to sufficiently investigate the phenomenon because they lacked instruments that could measure activity in its surface and atmosphere.

In their latest study, the research team collected data using the Focusing Optics X-ray Solar Imager (FOXSI-2) sounding rocket, a rocket payload composed of seven telescopes specifically designed to study the solar surface, to test their theory that very small flares on the Sun’s surface could be heating up the corona.

FOXSI studies solar radiation and particle acceleration in the corona by observing and collecting X-ray data over periods of just six to seven minutes.

The first FOXSI rocket was launched in 2012 and the second, from which the research team collected data, was launched two years later.

According to the researchers’ theory, these flares, which are actually small explosions, infuse the corona with heat. Until now, even the most sophisticated instruments could not detect such small solar flares.

Solar flares are known to emit X-rays, so the scientists focused on coronal X-ray emissions. These were found to be highly energetic, lending support to the theory.

No standard solar flares were visible in the part of the Sun studied with FOXSI-2. This means the X-rays detected have to be coming from nanoflares, composed of superheated plasma, within the corona.

FOSXI-3, a sounding rocket with even more sensitive equipment capable of detecting the faintest X-rays, is scheduled for launch next year, the researchers note, adding it might find further support for their theory.

Further assistance could come from the planned launch of a satellite specifically designed to detect nanoflares.

To actually prove their theory correct, scientists will need to successfully pinpoint the source of the X-rays being emitted from the corona.

Findings of the study have been published in the journal Nature Astronomy.





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