Parker observes a powerful coronal mass ejection of interplanetary dust – Parker Solar Probe

On September 5, 2022, NASA’s Parker Solar Probe gracefully cruised through one of the most powerful coronal mass ejections (CMEs) ever recorded—not only an impressive engineering feat, but a major boon to the scientific community. Parker’s coronal ejection flight helps prove a 20-year-old theory about coronal ejections interacting with interplanetary dust, with implications for space weather predictions. The results were recently published in the Astrophysical Journal.

A 2003 paper hypothesized that a CME might interact with interplanetary dust in orbit around our star, and might even carry the dust outward. Coronal mass ejections are massive explosions from the Sun’s outer atmosphere, or corona, that help drive space weather, which can endanger satellites, disrupt communications and navigation technologies, and even destroy power grids on Earth. Knowing more about how these events interact with interplanetary dust could help scientists better predict how quickly a coronal ejection will travel from the Sun to Earth, and predict when a planet could see its impact.

Parker has now observed this phenomenon for the first time.

“These interactions between CMEs and dust have been theorized for two decades, but were not observed until Parker Solar Probe saw that CMEs act like a vacuum cleaner, removing dust from road”. Applied Physics Laboratory (APL) in Laurel, Maryland, is the lead author of this paper. APL built and operates the spacecraft.

This dust is made up of small particles from asteroids, comets and even planets, and is found throughout the solar system. A type of faint glow called zodiacal light, which can sometimes be seen before sunrise or after sunset, is a manifestation of the interplanetary dust cloud.

The CME displaced dust all the way to about 6 million miles from the Sun — about one-sixth of the distance between the Sun and Mercury — but was almost immediately replenished by interplanetary dust floating through the solar system.

Parker’s in situ observations were crucial to this discovery, because determining dust dynamics following a CME is challenging from a distance. According to the researchers, Parker’s observations could also provide insight into related phenomena at the bottom of the coronal, such as coronal dimming caused by low-density regions in the coronal that often appear after a coronal eruption.

Scientists observed the interaction between coronal ejections and dust through decreased brightness in images from Parker’s Wide-field Imager for Solar Probe (WISPR) camera. This is because interplanetary dust reflects light, amplifying the brightness where the dust is.

Parker Solar Probe’s Wide Field Imagery for Solar Probe (WISPR) camera monitors the spacecraft’s passage through a massive coronal mass ejection on September 5, 2022. CMEs are massive explosions of plasma and energy from the Sun’s corona that drive space weather.
Source: NASA/Johns Hopkins APL/Naval Research Laboratory

To determine where the brightness drop occurred, the team had to average the background brightness of the WISPR images across several similar orbits, while filtering out natural brightness variations that occur due to solar fluxes and other changes in the solar corona.

“Parker orbited the Sun four times at the same distance, which allows us to compare data from one path to another very well,” Steinborg said. “By removing brightness variations due to coronal transitions and other phenomena, we were able to isolate variations caused by dust depletion.”

Since scientists only observed this effect in connection with the September 5 event, Steinborg and the team hypothesized that dust depletion might only occur with the strongest CMEs.

However, studying the physics behind this interaction may have implications for space weather prediction. Scientists are just beginning to understand that interplanetary dust affects the shape and speed of CMEs. But more studies are needed to better understand these interactions.

Parker completed his sixth flyby of Venus, using the planet’s gravity to propel himself closer to the Sun on his next five approaches. This occurs when the Sun itself approaches solar maximum, the period in the 11-year solar cycle when sunspots and solar activity are most abundant. As the Sun becomes more active, scientists hope they will have the opportunity to see more of these rare phenomena and explore how they affect the environment of Earth and the interplanetary medium.

The Parker Solar Probe was developed as part of NASA’s Living With a Star program to explore aspects of the Sun-Earth system that directly impact life and society. The Living with a Star program is managed by the agency’s Goddard Space Flight Center in Greenbelt, Maryland, for NASA’s Science Mission Directorate in Washington. APL designed, built, operated the spacecraft and managed the mission for NASA.

By Ashley Hume
Johns Hopkins Applied Physics Laboratory

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