Imagine a child’s drawing of the sun. A round yellow ball with straight rays of light beaming outwards. It turns out this depiction could be more accurate than you thought.
The discovery of solar wind – the constant flow of charged particles from the sun – was made in the 1950s. These flows originate near the sun and are structured in distinct rays, emanating outwards, until they reach the edge of the sun’s upper atmosphere. And this is where they change: the particles transitioning from straight, distinct rays into a gusty and turbulent solar wind as it approaches the Earth.
Scientists have never understood the details of this transition, until now. NASA’s Solar Terrestrial Relations Observatory (STEREO) has allowed scientists to create an image of the edge of the sun where the transition occurs.
The findings, published in the Astrophysical Journal, can help scientists learn more about our solar system and the space environment we exist in.
“Now we have a global picture of solar wind evolution,” said Nicholeen Viall, a co-author of the paper and a solar scientist. “This is really going to change our understanding of how the space environment develops.”
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How does it work?
The sun and its atmosphere are made up of plasma, a mixture of positively and negatively charged particles that have separated at extremely high temperatures and that travel along magnetic field lines.
This plasma streams out from the sun’s outer atmosphere and fills the solar system, but it changes as it moves farther away from the sun.
Craig DeForest, lead author of the study and a solar physicist, noted that the magnetic field strength drops faster than the pressure of the material the further it is from the sun.
“Eventually, the material starts to act more like a gas, and less like a magnetically structured plasma,” DeForest wrote.
Scientists had previously believed that magnetic forces were dominant at the corona’s edge, and this research has shown them to be correct.