NASA’s Parker Solar Probe uncovered clues about the origins of the solar wind

This finding is helping scientists better understand the 60-year-old mystery.

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Understanding the solar wind is fundamental to understanding our solar system and others throughout the universe. Made of electrons, protons, and heavier ions, the solar wind courses through the solar system at roughly 1 million miles per hour.

Although, what heats and accelerates the solar wind, remains a mystery. A new study is helping scientists solve this mystery and uncover significant new clues about the origins of the solar wind. Scientists with NASA’s Parker Solar Probe mission have discovered that the solar wind could be largely fueled by small-scale jets, or “jetlets,” at the base of the corona.

Jetlets are known to be caused by a process known as magnetic reconnection, which occurs as magnetic field lines become tangled and explosively realign. In the solar corona, reconnection creates these short-lived jets of plasma that pass energy and material into the upper corona, which escape across the solar system as the solar wind.

Nour Raouafi, the study lead and the Parker Solar Probe project scientist at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, said, “This new data shows us how the solar wind gets going at its source. You can see the flow of the solar wind rising from tiny jets of million-degree plasma all over the base of the corona. These findings will have a huge impact on our understanding of the heating and acceleration of the coronal and solar wind plasma.”

The solar wind often blows continuously at Earth. Therefore, scientists have been searching for a consistent source of the Sun that may sustainably drive the solar wind. The latest research suggests that the solar wind may be predominantly generated and fuelled by discrete jetlets that sporadically erupt into the lower region of the corona. Even while each jetlet is only a few hundred miles long, its combined mass and energy may be sufficient to produce solar wind.

Craig DeForest, a solar physicist at the Southwest Research Institute in Boulder, Colorado, and coauthor on the new paper, said, “This result implies that essentially all of the solar wind is likely released intermittently, becoming a steady flow in much the same way that the individual clapping sounds in an auditorium become a steady roar as an audience applauds. This changes the paradigm for how we think about certain aspects of the solar wind.”

Scientists mainly used observations from the Solar Dynamics Observatory (SDO) and the Solar Ultraviolet Imager (GOES-R/SUVI) instrument and high-resolution magnetic field data from the Goode Solar Telescope at the Big Bear Solar Observatory in California to study the jetlets and magnetic fields. Switchbacks, which are magnetic zig-zag formations in the solar wind, are a phenomenon that was initially noticed by Parker Solar Probe and served as the inspiration for the entire study.

A composite video from NASA’s Solar Dynamics Observatory and NOAA’s Geostationary Operational Environmental Satellite – R Series Solar Ultraviolet Imager instrument shows small-scale jetlet activity at the base of the solar corona, or the Sun’s upper atmosphere, and its extension to higher altitudes. This can be seen in the wavy structures emanating from the surface of the Sun. The observations were made over the course of approximately 10 hours on April 28, 2021. Credits: NASA/SDO/GOES-R

The scientists could comprehend the collective behavior of the jetlets thanks to the combination of observations from numerous viewpoints, their high resolution, and the close-up observations made by Parker Solar Probe.

Judy Karpen, a coauthor on the paper and heliophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said, “Previously, we could not detect enough such events to explain the observed amount of mass and energy streaming from the Sun. But the improved resolution of the observations and meticulous data processing enabled the new findings.”

The findings demonstrated the presence of jetlets throughout the lower solar atmosphere on the entire Sun. In contrast to other phenomena that wax and wane with the 11-year cycle of solar activity, such as solar flares and coronal mass ejections, they are thus a tenable driver for the continuous solar wind. The scientists also estimated that the energy and mass created by the jetlets might account for the majority, if not the entirety, of the energy and mass observed in the solar wind.

Raouafi said“The tiny reconnection events we observed are, in a way, what Eugene Parker proposed over three decades ago. I am convinced we are on the right path toward understanding the solar wind and coronal heating.”

Continued observations from Parker Solar Probe and other instruments, such as NASA’s Polarimeter to Unify the Corona and Heliosphere, or PUNCH, and the Daniel K. Inouye Solar Telescope, will help scientists confirm whether jetlets are the main source of solar wind.

Journal Reference:

  1. Nour E. Raouafi, G. Stenborg, et al. Magnetic Reconnection as the Driver of the Solar Wind. The Astrophysical Journal. DOI: 10.48550/arXiv.2301.00903
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