Understanding the Sun - What the Parker Solar Probe Changes

NASA launched the Parker Solar Probe (PSP) in 2018 on an extraordinary mission to conduct close-up studies of the Sun. In December 2024, on its 22nd orbit¹, the PSP, was only an unprecedented thirty-eight million miles from the surface of the sun within its atmosphere, where it was able to perform unparalleled scientific observations with the potential to transform our knowledge of the Sun.

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Studying the Sun Up Close

The primary objective of gathering data closer to the sun is to get a better understanding of the sources of solar interaction, and space weather, as well as identify the particles projected from the sun towards the Earth and how they interact with the electrical systems and technologies crucial for life on Earth^{1, 2}. Knowledge about how stars function throughout the cosmos can also help in the quest to find other habitable worlds.

Decades of research and development culminated in the launch of the PSP, an extraordinary feat in space exploration. NASA named the PSP in honor of the renowned scientist Eugene Parker, who first predict the existence of solar winds³.

Once launched from Earth, the PSP had to withstand the extreme cold conditions in space during its journey to the sun and then the extreme hot environments surrounding the surface of the sun. To enable PSP to approach the Sun, its speed had to be significantly reduced. This was accomplished by using the gravitational field of Venus over seven flybys. 

Mission Objectives

Specially designed instruments were mounted on the PSP to conduct three main scientific objectives set forth by NASA for the mission.  These mission objectives were to investigate the reason why solar winds accelerate, to trace the energy flow that heats up the solar corona, and to study the sources of solar energetic particles.

Breakthrough Discoveries and Implications for Space Research

Three years into its mission, in December 2021, PSP returned its first measurements from inside the sun’s atmosphere.

Using the Solar Wind Electrons Alphas and Protons investigation (SWEAP) instrument, PSP was able to examine the Alfvén critical surface, the location where solar material attached to the Sun gets ejects and transforms into solar winds³. PSP oscillated along the corona boundary multiple times during its initial approach providing data that demonstrated that the Alfvén critical surface was not formed smoothly as initially theorized, but instead, the surface is wrinkled by dips and spikes. The wrinkles were found to be caused by coronal streamers, enormous plumes of solar material that rise through the Sun's atmosphere.

Another device on the PSP called FIELDS has the capability to detect solar radio emissions, plasma wave spectra and polarization characteristics, direct current, and fluctuating magnetic and electric fields^3,4. From measurements taken by FIELDS, scientists discovered rapid flips in the Sun's magnetic field that switched direction in a zigzag pattern. This phenomenon, called switchbacks, lined up with magnetic "funnels" on the solar surface, according to the data. These funnels form between a feature on the sun known as supergranules. Supergranules are gigantic bubbles on the Sun where hot plasma cycles through heating to the top and cooling back down.  Analysis of the data collected indicates that the solar wind is driven by magnetic reconnections during these events.

The Integrated Science Investigation of the Sun (ISʘIS) evaluates the most energetic particles that exit the Sun, known as solar energetic particles (SEP)^3,5. The ISʘIS consists of two detectors, the Energetic Particle Instrument – Low Energy (EPI-Lo), and the Energetic Particle Instrument – High Energy (EPI-Hi). Protons, ions, and electrons of various energies can be measured by both instruments.

According to ISʘIS, SEPs are far more frequent than expected, and include a greater variety of particle kinds than anticipated. It was also observed that the switchbacks might alter their trajectories from the sun.

Additionally, PSP has made other discoveries throughout the inner solar system. While some observations yielded surprising information about solar energetic particles, others demonstrated how massive solar explosions known as coronal mass ejections clear up dust as they move throughout the solar system. The first full image of Venus' orbital dust ring has also been captured by PSP flybys.

Future Outlook

PSP has already provided enough data to declare the mission a resounding success, but it continues to break records taking unprecedented measurements of the Sun.

The boundaries of space science are being pushed by each new dataset. In addition to Sun measurements, the Parker Solar Probe observed radio emissions from Venus' atmosphere, investigated comets, and even taken the first visible-wavelength pictures of the planet's surface.

Numerous ideas have already been verified by the data collected, and it has also revealed fresh mysteries about the Sun and scientists are looking forward to the information that will be gathered from upcoming flybys. It is anticipated that the Parker Solar Probe mission will last for several more years.

References

1. Raouafi, N.E., Matteini, L., Squire, J. et al. Parker Solar Probe: Four Years of Discoveries at Solar Cycle Minimum. Space Sci Rev 219, 8 (2023). https://doi.org/10.1007/s11214-023-00952-4
2. Johnson-Groh, M. (29 April 2022) "NASA’s Parker Solar Probe Makes History with Closest Pass to Sun." NASA. Available online at: https://science.nasa.gov/science-research/heliophysics/nasas-parker-solar-probe-makes-history-with-closest-pass-to-sun/
3. Hatfield, M. (29 April 2022) "Amazing Achievements from Parker Solar Probe." Parker Solar Probe. Available online at: https://blogs.nasa.gov/parkersolarprobe/2022/04/29/amazing-achievements-from-parker-solar-probe/
4. Huang, Jia, Justin C. Kasper, Davin E. Larson, Michael D. McManus, Phyllis Whittlesey, Roberto Livi, Ali Rahmati et al. "The Temperature, Electron, and Pressure Characteristics of Switchbacks: Parker Solar Probe Observations." The Astrophysical Journal 954, no. 2 (2023): 133.
5. Mitchelle, G., J. G. Mitchella, J. S. Rankinf, E. C. Roelofe, N. A. Schwadronh, E. C. Stoneb, J. R. Szalayf, and M. E. Wiedenbecki. "New Data from the ISʘIS Instrument Suite on Parker Solar Probe."

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