Many of the features seen on the Sun might look like tongues of flame or fiery eruptions, but there’s no fire or lava on the Sun – its energetic outbursts are driven by powerful magnetic fields that rise up from its internal regions and twist, loop, and coil far out into space.
In addition to these far-reaching lines there is a network of magnetic fields that cover the Sun’s “surface” (that is, its photosphere) like a web – a web outlined by the edges of large-scale features called supergranules. Created by rising zones of hot solar material, these 35,000km-wide “bubbles” on the photosphere carry bundles of magnetic regions to their edges, fueling the network.
What one team of researchers has now found , through long-term observations with the Hinode satellite, is that the supergranules are able to replenish the entire magnetic surface web in a surprisingly short time – only 24 hours.
The dominant model postulates that the magnetic fields of the surface web result from the decay of active regions (sunspots) and from invisible zones known as ephemeral regions, which provide a lot of flow but are not very common.*
The observations with Hinode have triggered a paradigm change because it has shown that ephemeral regions are too scarce to have significant impact.*
“In the course of forty hours we detected only two ephemeral regions, so their contribution to the web can not be more than 10% of the total flow. By contrast, the small elements in the intranetwork are continuous and clearly dominant,” said Milan Gosic from the Institute of Astrophysics of Andalusia, lead author of the study. (*Source)
The animation below shows magnetic packets (red) within supergranules flowing into the Sun’s magnetic web (blue).
This supergranule-powered magnetic web replenishment may also be responsible for the immense amount of heating seen in the Sun’s corona, where temperatures soar much higher than those found closer to the surface (aka the coronal heating problem).
“It is believed that the magnetic elements of the intranetwork and their interactions with the web might be responsible for the warming up of the outer layers of the Sun’s atmosphere, one of the most pressing unsolved problems of solar physics”, said Luis Bellot (IAA-CSIS), a co-author of the study.
The team’s findings have been published in The Astrophysical Journal.
Hinode (pronounced HEE-no-day) is an international mission to study the Sun. To accomplish this, the Hinode space observatory includes a suite of three science instruments – the Solar Optical Telescope, X-ray Telescope and Extreme Ultraviolet Imaging Spectrometer. The spacecraft is in a Sun-synchronous orbit around Earth at an altitude of about 700 km (438 miles).
Led by the Japan Aerospace Exploration Agency (JAXA) Hinode is a collaboration between the space agencies of Japan, the United States, the UK, and Europe. Learn more about Hinode here.