The sun tightly controls everything in the solar system, but it is not always the best at keeping the material in its own atmosphere under control. The wayward solar wind constantly erupts from our parent star, rushing past each planet until it is stopped by a headwind generated by stars outside the solar system.
New study published in the journal Letters in an astrophysical journal mapped the outer edge of the solar atmosphere for the first time, shedding light on the boundary where the solar wind escapes the sun's magnetic influence.
Data from NASA's Parker Solar Probe have now allowed astronomers to trace the precise boundaries of this boundary and understand its ever-changing nature throughout the solar cycle.
Read more: Neptune is the farthest planet from the Sun, but it still displays auroras
Solar Wind Journey
The Sun is always sending streams of charged particles (or plasma) out of the corona, the outermost layer of the atmosphere. The corona, which reaches temperatures exceeding 2 million degrees Fahrenheit, heats and accelerates particles that move at such high speeds that they are able to escape the Sun in the form of solar wind.
Eventually, the charged particles break through the Alfven surface, the boundary of the Sun where the solar wind becomes faster than magnetic waves. The solar wind then travels around the solar system, taking with it some of the sun's energy. magnetic field which was embedded in the plasma.
At this point, the solar wind has no chance of returning under the influence of solar gravity, sweeping past planet after planet. Earth's magnetosphere blocks most passing wind, but some solar storms are powerful enough to create auroras or interfere with satellites.
The solar wind reaches the end of its journey at the heliopause, a region bordered by a vast expanse of interstellar gas and dust. According to NASA, the solar wind here is not strong enough to withstand the wind pressure of other stars in our galaxy.
Mapping the Sun's Boundary
Parker Solar Probewhich was launched in 2018 to study the Sun, has now confirmed how Alfvén's surface changes over time. Researchers involved in the new study examined data collected by the Solar Wind Alphas and Protons (SWEAP) instrument, allowing them to observe the structure of the outer edge of the Sun.
“Previously, we could only estimate the edge of the Sun from afar, without being able to check whether we had the right answer, but now we have an accurate map that we can use to navigate it as we study it,” said lead author Sam Badman, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, in statement.
“And, importantly, we can also observe its changes and compare those changes with close-up data. This gives us a much clearer picture of what is actually happening around the Sun,” Badman added.
Scientists know that the shape and size of Alfvén's surface varies with the 11-year solar cycle; it grows during solar maximum (the period of peak solar activity) and, conversely, contracts during solar minimum (the period of lowest solar activity). However, data from the Parker Solar Probe has clarified what is happening as the boundary expands.
“As the Sun goes through cycles of activity, we see that the shape and height of the Alfven surface around the Sun becomes larger and also sharper. This is actually what we have predicted in the past, but now we can confirm it directly,” Badman said.
Answers to solar secrets
According to the researchers, these maps of Alfvén's surface may reveal solar mysteries that still remain unanswered. This could help astronomers understand the processes occurring in the Sun's atmosphere; One of the key questions they have now is why the corona is so hot.
The maps could also lead to more accurate solar wind models that explain how space weather affects Earth and other planets.
The researchers' work is not finished yet; When the next solar minimum arrives around 2030, they plan to return to the solar corona to see what happens in the second half of the solar cycle.
Read more: Observations of a 2,700-year-old total solar eclipse provide insight into our ancient solar system
Article sources
Our writers at Discovermagazine.com use peer-reviewed research and high-quality sources for their articles, and our editors review scientific accuracy and editorial standards. Review the sources used below for this article:
