The human race has never been so close: The "Parker Solar Probe" spacecraft has approached it on 24 million kilometers, still a considerable distance. However, the small device has to withstand temperatures of more than a thousand degrees. Now researchers were able to evaluate the first data, which were published in four articles in the journal "Nature".
"We were shocked at how diverse the sun's corona is at close range," says study author Justin Kasper of the University of Michigan. What looks like Earth in a total eclipse of the sun like a uniform halo is in reality like a hidden object of fierce streams of radiation, plasma waves, and vibrating magnetic fields.
"Parker Solar Probe" was launched in 2018 and aims to clarify two fundamental questions:
Why does the solar atmosphere get hotter as you move further away from the star? The surface is only 5500 degrees hot, in the corona, however, prevail temperatures of up to 5.6 million degrees. To date, researchers are not exactly sure why that is.
The second important question is what drives solar winds – a stream of protons, electrons, and other particles that the corona shoots toward the earth, and that can severely disrupt the earth's power grid and paralyze communications satellites. Astronomers hope that the probe data will give them better predictions of such storms.
All questions could not answer the new data, but they provided a surprising insight into the solar atmosphere. Earlier missions had shown that the solar wind accelerates when it leaves the corona. So far, it was unclear why that is. However, one of the published studies has shown that changes in the sun's magnetic field drive the winds in addition. Recorded speeds were well above what previous model calculations had shown.
In the video: The launch of "Solar Parker Probe"
AP / Steve Gribben / Johns Hopkins APL / NASA
The researchers also found a possible explanation why the sun's corona is much hotter than its surface. "When you approach the sun, you see plasma waves that have four times the energy of the others," explains Kasper. They reach top speeds of up to 480,000 kilometers per hour. "They are so strong that they can reverse the direction of the magnetic field," Kasper continues. That could be the explanation why the corona is heating up.
Another study dealt with particularly slow solar winds. "Slow" in this case means less than 500 kilometers per second. Until now, it was unclear where these originated. The new research now shows that they probably come from holes in the corona that lie at the equator of the sun.
In the next five years, "Parker Solar Probe" will even approach the sun on six million kilometers. Researchers expect that the sun will be particularly active in time.