Data collected by NASA's Solar Parker mission in the overflights closer to the Sun of a spaceship, they indicate that the coronal holes appear to be the source of the slow solar wind.
That data has allowed solar physicists map the source of this main component of the solar wind that continually splashes the Earth's atmosphere, while revealing strange investments of magnetic fields that could be accelerating these particles towards our planet, which they publish in the magazine ‘Nature’.
These accelerated particles interact with the Earth's magnetic field, generating the colorful auroras. But they also have the potential to damage the electrical network and telecommunications networks on the Earth's surface, threaten satellites in orbit and perhaps endanger astronauts in space.
The more solar physicists understand about the sun's magnetic environment and how it throws the solar wind particles toward the planets, the better they can predict events and prevent damage.
“There was a great space weather event in 1859 that destroyed the telegraph networks on Earth and one in 1972 that activated the naval mines in North Vietnam, only by the electric currents generated by the solar storm”, Recalls Stuart Bale, Professor of Physics at the University of California and lead author of an article about the new results of the FIELDS probe experiment.
"We are a much more technological society than in 1972, communications networks and the electricity grid on Earth are extraordinarily complex, so the great perturbations of the sun are potentially very serious," he continues. If we could predict the space weather, it could turn off or isolate parts of the power grid, or turn off satellite systems that could be vulnerable. ”.
One of the main objectives of the Parker solar probe is to discover the source of the “slow” solar wind and how it accelerates in the hot atmosphere of the sun: the 1 million degree solar corona. The solar wind consists of charged particles, mainly protons and helium nuclei, that travel along the lines of the sun's magnetic field.
It is known that the so-called “fast” solar wind, with a speed of between 500 and 1,000 kilometers per second, comes from large holes in the solar corona at the north and south poles of the sun. But the origin of the “slow” solar wind, which is denser but about half the speed of the “fast” solar wind, is less understood.
Data from the first close encounter of the probe (the probe has had two other encounters during the closest approach, or perihelion, of its orbit around the sun) reveals a great deal of new physics.
"The first three meetings of the solar probe that we have had so far have been spectacular”, Admits Bale, the principal investigator of FIELDS.
“We can see the magnetic structure of the crown, which tells us that the solar wind is emerging from small coronal holes; we see impulsive activity, large jets or setbacks that we believe are related to the origin of the solar wind; we see instability (the gas itself is unstable and generates waves), and we are also surprised by the ferocity of the dust environment in the internal heliosphere ”, Add.
During each close encounter, the probe was parked for a week above a crown hole that transmitted solar wind particles along the magnetic field lines beyond the probe, giving the instruments on board the probe an unprecedented view of what was happening on the solar surface below.
Thanks to the extreme ultraviolet mapping of the sun by other spacecraft, such as STEREO, Bale and his colleagues were able to track the wind and magnetic fields to a source, the coronal holes, strongly suggesting that these holes are the source of the slow solar wind. Coronal holes, which are related to sunspots, are cooler and less dense areas than the surrounding crown.
The unexpected was a series of turns in the magnetic field while passing through the spacecraft. During these periods, the magnetic field suddenly reversed 180 degrees and then, seconds to hours later, receded.
"These interruptions are probably associated with some kind of plasma jets," Bale says. My feeling is that these interruptions or jets are fundamental to the problem of solar wind warming. ”
Another surprise was the dust that splashed the spacecraft repeatedly during each overflight in the perihelion, the point in the orbit where the spacecraft was closest to the sun. Probably smaller than a micron, which is one thousandth of a millimeter, the dust particles are probably remains of asteroids or comets that melted near the sun and left their dust trapped.
That dust is now orbiting the sun, and Bale suspects that much of it, hitting the spacecraft, is expelled outward by light pressure and destined to escape completely from the solar system.
Bale adds that studying Earth's solar wind is like studying the source of a waterfall near the bottom, where turbulence obscures what happens at the top.
“Now, with the Parker solar probe, we are getting closer and closer to the top of the waterfall, and we can see that there is an underlying structure – it highlights -. At the source, what we see is something that is consistent with impulsive jets. You have a small hole, a coronal hole, and the solar wind out there in a smooth flow. But then, in addition to that, there are jets. When it reaches Earth, everything is mixed. ” Ep
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