NASA’s Parker Solar Probe has recently ventured through a formidable coronal mass ejection (CME), presenting groundbreaking findings that lend support to a theory established two decades ago regarding CME interactions with interplanetary dust. This breakthrough holds significant importance for advancing space weather predictions.
On September 5, 2022, NASA’s Parker Solar Probe undertook a remarkable journey through one of the most potent coronal mass ejections ever documented. This achievement is not only a testament to engineering prowess but also a momentous contribution to the scientific community. The probe’s traversal through the CME is substantiating a theory dating back 20 years, elucidating how CMEs engage with interplanetary dust and its implications for space weather forecasting. These findings have been recently published in The Astrophysical Journal.
The Interplay Between CMEs and Interplanetary Dust
In 2003, a research paper proposed the idea that CMEs could interact with interplanetary dust encircling our Sun, potentially carrying this dust outward. CMEs, which are colossal eruptions from the Sun’s corona, play a pivotal role in driving space weather phenomena. Such events can jeopardize satellites, disrupt communication and navigation systems, and even cause disruptions in terrestrial power grids. A more profound understanding of how CMEs interact with interplanetary dust could aid scientists in forecasting the speed at which CMEs can traverse from the Sun to Earth, predicting their potential impact on our planet.
Parker Solar Probe has now provided the first-ever observations of this phenomenon. Guillermo Stenborg, an astrophysicist at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, and the lead author of the paper, stated, “These interactions between CMEs and dust were theorized two decades ago but had not been observed until Parker Solar Probe viewed a CME act like a vacuum cleaner, clearing the dust out of its path.” The APL was responsible for constructing and operating the spacecraft.
Implications for Interplanetary Dust
Interplanetary dust comprises minute particles originating from asteroids, comets, and even planets, distributed throughout our solar system. One manifestation of this dust cloud is the zodiacal light, a faint glow occasionally visible before sunrise or after sunset. The CME displaced this interplanetary dust to a distance of approximately 6 million miles from the Sun, equivalent to about one-sixth of the Sun-to-Mercury distance. Remarkably, the dust was replenished almost immediately by interplanetary dust particles navigating through the solar system.
In-situ observations from Parker were instrumental in making this discovery, as characterizing dust dynamics in the wake of CMEs proves challenging from a distance. According to researchers, Parker’s observations could also shed light on related phenomena occurring lower down in the corona, such as coronal dimming induced by low-density areas that often manifest after CMEs erupt.
Observation Techniques and Future Insights
Scientists identified the interaction between the CME and dust through a reduction in brightness in images captured by Parker’s Wide-field Imager for Solar Probe (WISPR) camera. This decrease in brightness occurred because interplanetary dust reflects light, amplifying brightness in areas where dust is present.
To pinpoint this reduction in brightness, the team had to calculate the average background brightness of WISPR images across several similar orbits, filtering out normal variations attributed to solar streamers and other changes in the solar corona.
Stenborg noted, “Parker has orbited the Sun four times at the same distance, allowing us to compare data from one pass to the next very well. By removing brightness variations due to coronal shifts and other phenomena, we were able to isolate the variations caused by dust depletion.”
Although scientists have observed this effect solely in connection with the September 5 event, Stenborg and the team speculate that dust depletion might occur only during the most powerful CMEs. Nonetheless, delving into the physics of this interaction holds promise for improving space weather prediction. Scientists are just beginning to grasp how interplanetary dust influences the shape and velocity of a CME, and further studies are necessary to gain a deeper understanding of these interactions.
Parker Solar Probe’s journey continues as it completed its sixth Venus flyby, harnessing the planet’s gravity to draw closer to the Sun for its next five close approaches. This coincides with the Sun’s approach to solar maximum, a phase in the Sun’s 11-year cycle marked by increased sunspot and solar activity. As solar activity intensifies, scientists anticipate the opportunity to witness more of these rare phenomena and explore their potential effects on our Earth’s environment and the interplanetary medium.
Reference: “Investigating Coronal Holes and CMEs as Sources of Brightness Depletion Detected in PSP/WISPR Images” by Guillermo Stenborg, Evangelos Paouris, Russell A. Howard, Angelos Vourlidas, and Phillip Hess, May 31, 2023, The Astrophysical Journal. DOI: 10.3847/1538-4357/acd2cf
Parker Solar Probe was developed as part of NASA’s Living With a Star program, designed to explore facets of the Sun-Earth system that directly impact life and society. This program is overseen by NASA’s Goddard Space Flight Center in Greenbelt, Maryland, on behalf of NASA’s Science Mission Directorate in Washington. The Applied Physics Laboratory (APL) designed, constructed, and operates the spacecraft while managing the mission for NASA.