Scientists on NASA’s Parker Solar Probe mission have discovered important new clues about the origin of the solar wind, the constant stream of charged particles released from the Sun that fills the Solar System.
Observations from many space and ground-based observatories show that the solar wind may be mainly fueled by small jets, or “jets”, at the base of the corona, the Sun’s upper atmosphere. The discovery helps scientists better understand the 60-year-old mystery of what heats and accelerates the solar wind.
“This new data shows us how the solar wind develops at its source,” said Noor Raouafi, study leader and Parker Solar Probe project scientist at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland. “You can see the solar wind stream rising from tiny jets of plasma with millions of degrees across the base of the corona. These discoveries will have a huge impact on our understanding of the heating and acceleration of coronal and solar wind plasma.”
Understanding the solar wind is fundamental to our understanding of our solar system and others throughout the universe – and is a primary science goal of the mission Parker Solar Probe. The solar wind, made up of electrons, protons, and heavy ions, moves through the solar system at about 1 million miles per hour. When the solar wind interacts with the Earth’s magnetic field, it can create stunning auroras and disrupt GPS and communications systems. Eventually, the solar wind and stellar winds in other solar systems may also influence the composition and evolution of planetary atmospheres – even affecting the habitability of planets.
Strength in numbers
On Earth, the solar wind is usually a steady breeze. Therefore, scientists were looking for a permanent source on the Sun that could continuously feed the solar wind. However, new findings accepted for publication in the Astrophysical Journal and published on ArXiv, an online preprints site, show that the solar wind can be largely fed and fueled by individual jets that periodically erupt into the lower part of the corona. Although each jet is relatively small – only a few hundred miles long – their combined energy and mass can be enough to create the solar wind.
“This result means that essentially all of the solar wind is likely released intermittently, becoming a steady stream in much the same way that individual claps in an auditorium turn into a steady roar as the audience applauds,” said Craig DeForest, a solar physicist. . at the Southwest Research Institute in Boulder, Colorado, and co-authored the new paper. “It changes the paradigm of how we think about certain aspects of the solar wind.”
The jets, first observed more than a decade ago, are known to be caused by a process known as magnetic reconnection, which occurs when magnetic field lines become entangled and explosively realigned. Reconnection is a common process in charged gases called plasma, and is observed throughout the universe from the Sun to the space around black holes. In the solar corona, reconnection creates these short-lived jets of plasma that pass energy and material into the upper corona, which flows out through the solar system as the solar wind.
To study jets and magnetic fields, scientists mainly used observations from Solar Dynamics Observatory (SDO) and the device Solar Ultraviolet Imager Geostationary Operational Environmental Satellite-R series (GOES-R/SUVI), as well as the high-resolution magnetic field. Data from the Goode solar telescope Big Bear Solar Observatory in California. The entire study was based on a phenomenon first observed by the Parker Solar Probe called switching – magnetic zigzag structures in the solar wind. The combination of observations from multiple viewpoints, as well as the high resolution of these images and close-up observations by the Parker Solar Probe, helped scientists understand the collective behavior of the jets.
“Previously, we couldn’t detect enough of these events to explain the observed amount of mass and energy coming out of the Sun,” said Judy Karpen, co-author of the paper and a heliophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “But improved observational resolution and careful data processing have made new discoveries possible.”
Observations have shown that gels are present in the lower layers of the solar atmosphere throughout the Sun. This makes them a reliable driver of the persistent solar wind, unlike other phenomena that wax and wane with the 11-year cycle of solar activity, such as solar flares and coronal mass ejections. In addition, the scientists estimate that the energy and mass produced by jets could provide most, if not all, of the energy and mass seen in the solar wind.
A decade of breakthrough
NASA’s Solar Dynamics Observatory shows the small jets at the base of the solar corona, or the upper layers of the Sun’s atmosphere. You can see jets coming from the surface of the Sun. Observations were made for approximately 10 hours on April 28, 2021.
The solar wind was first proposed in the late 1950s by visionary scientist Eugene Parker, namesake of the Parker Solar Probe. In 1988, Parker suggested that the corona could be heated by “nanoflares,” tiny explosions in the solar atmosphere. Parker’s theory eventually became the leading candidate to explain the heating and acceleration of the solar wind.
“The tiny reconnection events we observed are, in some ways, what Eugene Parker proposed more than three decades ago,” Raouafi said. “I am convinced that we are on the right track to understanding the solar wind and coronal heating.”
Continued observations with the Parker Solar Probe and other instruments, such as NASA’s Corona-Heliosphere Unification Polarimeter, or PUNCH, and the Daniel K. Inouye Solar Telescope will help scientists confirm whether the jets are the main source of the solar wind.
“These findings make it much easier to explain how the solar wind is accelerated and heated,” DeForest said. “We’re not done with the puzzle yet, but this is a big step forward in understanding the central mystery of solar physics.”
