In 1958, physicist Eugene Parker predicted the existence of solar winds, but it took four years for the Mariner probe, which was heading to Venus, to confirm their existence. Since then, one of the Most frequently asked questions by astronomers is how it is possible that the solar wind (a stream of energetic particles that flows from our star towards the solar system), maintains its energy once it leaves the Sun.
Now, thanks to the collaboration of the two largest space agencies, NASA and ESA (European Space Agency), the answer may have been discovered: knowledge that is a crucial piece of the puzzle to help scientists better forecast solar activity between the Sun and Earth.
In a study published in Science, a team of scientists led by Yeimy Rivera of the Smithsonian Astrophysical Observatory provides compelling evidence that The fastest solar winds are driven by waves or zigzags magnandTicoslarge twists in the magn fieldandTico, close to the Sun.
“Our study addresses a huge open question about how the solar wind is energized and helps us understand how the Sun affects its environment and ultimately Earth,” Rivera said in a statement. “If this process occurs on our local star, This is likely to fuel winds from other stars throughout the galaxy.the Milky Way and beyond, and could have implications for the habitability of exoplanets.”
Previously, NASA’s Parker Solar Probe found that these zigzags were common throughout the solar wind. This probe, the first spacecraft to enter the Sun’s magnetic atmosphere in 2021, allowed scientists to determine that the zigzags are more defined and powerful near the Sun. However, Until now, scientists lacked experimental evidence that this interesting phenomenon (like the waves a whip draws before exploding on the target) really has enough energy to be important in the solar wind.
“About three years ago, I was giving a talk about how fascinating these waves are,” adds co-author Mike Stevens. “At the end, an astronomy professor stood up and said, ‘That’s great, but do they really matter??’”
To answer this, Rivera’s team had to use two different spacecraft. The first of these, the aforementioned Parker probe, is built to fly through the corona, or solar atmosphere. The second is the Solar Orbiter mission, shared by ESA and NASA, and is also in the process of being used to study the solar system. an orbit that takes it relatively close to the Sun.
The discovery was made possible by a coincidental alignment in February 2022 that allowed both the Parker Solar Probe like Solar Orbiter measured the same solar wind stream two days apart. Solar Orbiter was almost halfway to the Sun, while Parker skirted the edge of its magnetic atmosphere.
“At first we didn’t realize that Parker and Solar Orbiter were measuring the same thing. Parker saw this slower plasma near the Sun that was full of zigzag waves, and then Solar Orbiter recorded a fast current that had been heated and with very little wave activity – adds Samuel Badman, co-author of the study – When we connected the two, that was a real eureka moment.”
Scientists have long known that Energy moves through the solar corona and solar windat least in part, through what are known as “Alfvén waves.” These waves carry energy through a plasma, the superheated state of matter that makes up the solar wind.
However, it could not be measured in To what extent do Alfvén waves evolve and interact with the solar wind? between the Sun and Earth, until these two missions were sent closer to our star than ever before. And at the same time. Now, thanks to this, it is possible to directly determine how much energy is stored in the waves near the corona, and how much is carried by the waves as they move away from the Sun.
The new research shows that zigzag-shaped Alfvén waves provide enough energy to explain the documented heating and acceleration in the faster stream of solar wind as it moves away from the Sun. “It took us more than half a century to confirm that the acceleration and heating of Alfvén waves are important processes, and occur roughly the way we think they do“says John Belcher of the Massachusetts Institute of Technology (MIT) and one of those responsible for discovering Alfvén waves in 1971.
In addition to helping scientists to better forecast solar activity and space weatherthis information helps us explain the mysteries of the universe elsewhere and how Sun-like stars work.
“This discovery is one of the key pieces to answer the question of 50 years ago how the solar wind accelerates and heats up into the innermost parts of the heliosphere, bringing us closer to completing one of the primary science objectives of the Parker Solar Probe mission,” concludes Adam Szabo, science director for the Parker Solar Probe mission at NASA.