Clearest images of sun's atmosphere yet show coronal rain and dancing plasma
New images that are the highest resolution ever taken of the surface of the sun and its corona will help scientists solve mysteries about how storms on the sun develop. This could improve space weather forecasts and help prevent disruptions to technology on Earth.
The images were part of a recent study published in Nature Astronomy.
Anyone who has seen a total eclipse of the sun has been witness to the glowing halo around our star known as the corona. This envelope of extremely hot gas extends millions of kilometres out into space and is where violent eruptions take place. These bursts of electrically charged gas can blow off the sun and reach all the way to Earth, affecting satellites and power grids.
This glosses over one of the big mysteries about the sun. Scientists have not been able to entirely understand why the corona can be many times hotter than the surface of the sun itself. Something is pumping energy into the sun's atmosphere. One problem has been the dearth of observations of the corona at its base, where it meets the surface and where the violent activity originates. Nature provides brief glimpses during solar eclipses when the moon covers the bright surface of the sun allowing the dimmer corona to shine through, but continuous observations have been more difficult.
Telescopes on the ground trying to study weather on the sun have been hampered by our own weather. Turbulence in our atmosphere blurs images through the same effect that makes stars twinkle at night.
Now, however, new adaptive optics on the 1.6 metre Goode Solar Telescope in California has reduced the shimmering effect of our atmosphere by a factor of ten. This improvement allows us to see features at 63 kilometre resolution, which is closer than ever before. The trick was a flexible mirror that changes shape 2200 times per second, compensating and correcting for atmospheric distortion as it happens.
This has resulted in the highest resolution images and movies ever made of the boundary between the surface of the sun and the corona.
The stunningly beautiful images reveal what looks like a fluffy surface on the sun with giant loops of material rising up, seemingly dancing and twisting with the sun's magnetic field. Meanwhile, cooler coronal raindrops, which can be narrower than 20 kilometres wide, fall back down. The observations also show something scientists have never seen before: a plasma stream they're calling a "plasmoid" moving across the solar surface at 100 kilometres per second.
This is the region where solar flares and coronal mass ejections produce giant blobs of electrically charged material many times larger than the Earth, which blast off the sun and strike our planet's magnetic field. The result is beautiful northern and southern lights, but also a damaging effect on electronics in satellites and power surges in electrical grids causing blackouts.
A dramatic example of this effect came in 1989 when a coronal mass ejection caused the Quebec power grid to shut down, casting most of the province into darkness for nine hours. Since then, power systems have been hardened against such events, but with more dependence on GPS satellites, navigation systems could still be interrupted. Even astronauts on the International Space Station need to seek shelter in their spacecraft to avoid the harmful radiation effects of solar flares. Future astronauts on the moon will be under similar threats from solar storms.
Predicting violent solar events is challenging because the surface of the sun is a complicated, violent place that is ever changing, partly due to the fact that the equator of our star rotates faster than the poles. This causes turbulence in the hot gasses and twists the powerful magnet field into loops that can snap, releasing material into space. The sun also goes through cycles every 11 years where solar activity waxes and wanes. We are in a period of solar maximum at the moment, so monitoring its activity is important.
These new corrective lenses, which can also be fitted to other solar telescopes, will enable scientists to dive into the mystery of why the corona is so hot and how solar disturbances originate. This could improve predictions in space weather so warnings can be issued earlier.
As with weather on Earth, an accurate long-term weather forecast can be vital. Hopefully this will mean we see space weather coming more clearly.
cbc.ca
