The Parker Solar Probe from NASA has uncovered new clues to the long-standing mystery of why the outer atmosphere of the Sun, known as the corona, is much hotter than the surface of our star.
For decades, scientists have been puzzled over why the outer layer of the Sun’s atmosphere, or corona, heats up as it moves away from the Sun’s surface.
The Parker Solar Probe has completed its 20th flyby of the Sun last month, searching for clues to solve the decades-old mystery of why the Sun’s corona is hundreds of times hotter than its surface. (Image: Applied Physics Laboratory and Goddard Space Flight Center of NASA).
Now, thanks to data collected by NASA’s Parker Solar Probe, which has repeatedly flown past the Sun in search of clues to address the so-called “mystery of the coronal heating.”
During its first flyby of the Sun, its instruments detected a sudden reversal in the Sun’s magnetic field. Scientists refer to such instances as “switchbacks” and suspect they play a role in heating the corona, primarily by releasing magnetic energy contained within them as they move through the Sun and into space.
The corona is hundreds of times hotter than its “surface”
The mystery of the corona’s heating relates to the fact that the outer atmosphere of the Sun, the corona, is hundreds of times hotter than its “surface,” that is, the photosphere. Although the photosphere is millions of miles closer to the Sun’s core, where nuclear fusion reactions generate the heat and energy for our star.
Despite being cooler than the corona, the photosphere is responsible for most of the light from the Sun, completely “washing out” the light from the Sun’s atmosphere. Therefore, the Sun’s corona can only be seen when the light from the photosphere is blocked by a solar eclipse or by using a special tool called a coronagraph.
This means that to study the corona, the Parker Solar Probe must endure temperatures of about 1,400 degrees Celsius to get closer to the Sun.
The probe’s data indicates that switchbacks are a common phenomenon in the solar wind near the Sun. This finding suggests that the serpentine motion heating the corona may not originate from the Sun’s surface, ruling out one of the two main hypotheses regarding the source of this serpentine motion.
Scientists believe that “there may still be a triggering mechanism contributing to heating the outermost part of the Sun. Such a mechanism could be the explosive collision of chaotic magnetic field lines on the Sun’s surface.” Akhavan-Tafti stated.
This research enhances our understanding of how the Sun operates and may ultimately help scientists predict, detect, and prepare for solar storms.
This is the latest finding from NASA’s Parker mission since it began in 2018. Scientists hope that data from Parker’s journeys will reveal more about why the corona reaches millions of degrees.
