Parker Solar Probe Uncovers the Source of Solar Wind’s Incredible Speeds

New insights into the nature of the sun’s wind, which can travel at speeds exceeding 1 million miles per hour, have been gleaned from data collected by NASA’s Parker Solar Probe. These findings shed light on the mechanisms driving the fast solar wind, with potential implications for predicting solar eruptions, understanding cosmic wind phenomena, and aiding the search for habitable planets.

While Earth has experienced winds surpassing 200 miles per hour, the velocity of the sun’s wind far surpasses that. In a recent publication in the journal Nature on June 7, 2023, a team of researchers, co-led by James Drake from the University of Maryland, utilized data from the Parker Solar Probe to elucidate how the solar wind achieves speeds exceeding 1 million miles per hour. Their analysis revealed that the energy emanating from the magnetic field near the sun’s surface acts as a driving force for the rapid solar wind, which consists of ionized particles, or plasma, flowing outward from the sun.

Understanding the drivers of the sun’s wind has been a scientific endeavor since the 1950s, and in today’s interconnected world, it holds significant implications for Earth. The solar wind forms a protective magnetic bubble called the heliosphere, shielding the planets in our solar system from high-energy cosmic rays. However, the solar wind also carries plasma and a portion of the sun’s magnetic field, which can interact with Earth’s magnetosphere and cause disturbances, including geomagnetic storms.

Geomagnetic storms occur during periods of heightened solar activity, such as solar flares and coronal mass ejections, which involve the expulsion of large amounts of plasma into space. While these storms create captivating aurora displays near the Earth’s poles, at their most severe, they can disrupt power grids and global communications, posing risks to both infrastructure and astronauts in space.

According to Drake, comprehending the sun’s wind mechanism holds practical significance for Earth: “Winds carry lots of information from the sun to Earth, so understanding the mechanism behind the sun’s wind is important for practical reasons on Earth… It’s going to affect our ability to understand how the sun releases energy and drives geomagnetic storms, which are a threat to our communication networks.”

Previous studies hinted at the sun’s magnetic field playing a role in driving the solar wind, but the exact mechanism remained elusive. Earlier this year, Drake co-authored a paper proposing that the heating and acceleration of the solar wind are propelled by magnetic reconnection—a phenomenon that has been the focus of Drake’s scientific career.

The researchers revealed that the sun’s surface is adorned with small eruptions of hot plasma called “jetlets,” propelled upward by magnetic reconnection, which occurs when opposing magnetic fields intersect. This process triggers the release of substantial amounts of energy.

To delve further into these processes, the authors of the Nature paper examined data from the Parker Solar Probe, specifically analyzing the plasma emanating from the sun’s corona—the outermost and hottest layer. In April 2021, the probe achieved the unprecedented feat of entering the sun’s corona, and since then, it has been progressively approaching the sun. The data referenced in the study was collected at a distance of approximately 5.6 million miles from the sun, equivalent to 13 solar radii.

Drake highlighted the significance of the Parker Solar Probe’s proximity to the sun, stating, “When you get very close to the sun, you start seeing stuff that you just can’t see from Earth… We’re about as close as we’re going to get.”

Leveraging this new dataset, the authors of the study offered the first characterization of the bursts of magnetic energy occurring within coronal holes, which are regions of the sun’s magnetic field that appear as openings. The researchers demonstrated that the continuous process of magnetic reconnection between open and closed magnetic fields, known as interchange reconnection, generates a powerful release of magnetic energy. This release propels the outward flow of heated plasma, defying gravity and giving rise to the sun’s fast wind.

By comprehending these ongoing smaller energy releases on the sun, scientists hope to better understand and potentially predict larger, more hazardous eruptions that propel plasma into space. In addition to Earth’s implications, these findings have broad relevance in astronomy, particularly regarding winds generated by celestial objects throughout the universe. For instance, winds from stars play a crucial role in shielding planetary systems from galactic cosmic rays, which can influence habitability. Thus, this research not only enhances our understanding of the cosmos but also aids in the search for extraterrestrial life.

For more information on this study, refer to “Parker Solar Probe Plunges Into Fast Solar Wind and Discovers Its Source.”

Reference: “Interchange reconnection as the source of the fast solar wind within coronal holes” by S. D. Bale, J. F. Drake, M. D. McManus, M. I. Desai, S. T. Badman, D. E. Larson, M. Swisdak, T. S. Horbury, N. E. Raouafi, T. Phan, M. Velli, D. J. McComas, C. M. S. Cohen, D. Mitchell, O. Panasenco and J. C. Kasper, 7 June 2023, Nature.
DOI: 10.1038/s41586-023-05955-3

In addition to Drake, Marc Swisdak, a research scientist in UMD’s Institute for Research in Electronics and Applied Physics, contributed to this study.

This research was supported by NASA (Contract No. NNN06AA01C). The views expressed in this article do not necessarily represent those of the organization.

Frequently Asked Questions (FAQs) about solar wind

More about solar wind

• NASA’s Parker Solar Probe
• Nature paper: Interchange reconnection as the source of the fast solar wind within coronal holes
• NASA’s Parker Solar Probe Mission Overview
• NASA’s Parker Solar Probe: Plunging into the Sun’s Atmosphere