NASA’s Parker Solar Probe (PSP) was launched on August 12, 2018, with the goal of becoming the first spacecraft to touch the Sun while teaching us more about our host star than any spacecraft or solar instrument in human history. Now, a recent study submitted to The Astrophysical Journal discusses the incredible data that PSP collected on coronal mass ejections (CMEs) over a four-year period. This study holds the potential to help scientists and the public better understand the CMEs and how they contribute to space weather.
Here, Universe Today speaks with Dr. Tarik Mohammad Salman, who is a Postdoctoral Research Fellow at NASA and George Mason University and lead author of the study regarding the motivation behind the study, its most significant results, implications for future research, PSP contributions, and the importance of studying CMEs. So, what was the motivation behind this study?
“The PSP science data is a treasure trove as it samples the solar wind at uncharted radial distances from the Sun,” Dr. Salman tells Universe Today. “There have been numerous case studies of coronal mass ejections (CMEs) using PSP observations that provided new insights into the evolution of CMEs as the structures propagate farther from the Sun. We are in the sixth year of the PSP mission which provided us with a reasonable number of CME events to perform a statistical investigation. That was the motivation for this project to compile a catalog of CME events that PSP measured from 2018-2022 and also to investigate different perspectives of CME evolution in a statistical manner.”
For the study, PSP collected direct measurements of 32 interplanetary coronal mass ejections (ICMEs) between October 2018 and August 2022 and distances from the Sun ranging between 0.23 and 0.83 astronomical units (AU), with 1 AU being the distance between the Earth and the Sun, or approximately 150 million kilometers (93 million miles). Of the 32 measurements, four were discarded due to gaps in the data, leaving 28 CMEs successfully measured by PSP. The study’s objectives were to identify various aspects of CMEs, specifically pertaining to how they change as they travel farther from the Sun, also known as radial distance. So, what were the most significant results from this study?
Dr. Salman tells Universe Today, “A few results that I would like to highlight are that we observed the internal CME magnetic structure to become more complex with radial distance. We found the CME magnetic field strength to decrease at a lower rate than previous studies. We also saw that the expansion of the CME is important in the formation of the compression region ahead of it and the internal magnetic field has an influence on the short-scale fluctuations we find within the compression region.”
While the study of CMEs falls under the scientific field of solar physics, which studies how our entire Sun functions, scientists also classify CMEs as part of space weather, which studies the activity on the Sun’s surface and how it affects the surrounding environment. Space weather can wreak havoc on electronics, specifically communication satellites and power stations on Earth, with one of the most notable space weather events occurring in September 1859 known as the Carrington Event, which was caused by a massive solar storm that wreaked havoc on worldwide electrical grids and created spectacular auroras across the globe, as well, with the latter traditionally only being visible in the northern and southern latitudes. Therefore, what implications can this study have on future research regarding our Sun, and specifically space weather?
“The compiled catalog of CME events itself will be a valuable resource for performing future extensive case studies,” Dr. Salman tells Universe Today. “Understanding the evolution of CMEs is of paramount importance for space weather operations. This statistical investigation of different aspects of CME evolution is a step towards that as it validates previous approximations but also raises new questions that need to be explored further with a more robust data set in the future.”
After having its first solar encounter in October 2018, PSP has continued to smash records regarding its distance from our Sun. This includes achieving its closest distance of 7.26 million kilometers (4.51 million miles) on September 27, 2023, which is slated to be surpassed after its last flyby of Venus in November 2024. Science objectives for PSP include determining the solar corona processes responsible for producing the solar wind, gaining insight into the solar plasma and magnetic field properties, and learning more about additional energy particles emitted by the Sun.
The reason why PSP can travel so close to our Sun is due to its state-of-the-art solar shield comprised of a 11.43-centimeter-thick (4.5-inch-thich) carbon-composite shield capable of withstanding scorching temperatures up to 1,377 degrees Celsius (2,500 degrees Fahrenheit). While PSP has already broken records regarding its distance to the Sun, PSP is slated to come within 6.16 million kilometers (3.83 million miles) during its mission, which is planned to last a total of seven years. But how has PSP contributed to our understanding of our Sun and space weather?
“PSP is so important for us to advance our current understanding of CME evolution and space weather,” Dr. Salman tells Universe Today. “The questions of interest for space weather are will a CME impact Earth and whether it will have a southward field component to interact with the northward magnetic field of Earth. Our modeling frameworks depend on an initial characterization of the CME closer to the Sun (within 20 solar radii) based on which the models project the CME parameters when it impacts Earth.”
Dr. Salman continues, “The initial characterization is made based on CME remote-sensing imaging. What PSP is doing is providing direct measurements of CMEs in the initial phases of propagation. Adding to this are the widespread radial observations of PSP to make our statistical approximations more robust. This is how PSP is contributing to develop a more accurate picture of the CME propagation and evolution from closer to the Sun to Earth.”
CMEs have been observed for thousands of years in the form of auroras when the solar wind interacts with the Earth’s magnetic field near the planet’s surface. They are produced from the Sun’s corona in the form of massive discharges when solar plasma interacts with the Sun’s massive magnetic field and their velocities can range from 250 kilometers per second (155 miles per second) to almost 3,000 kilometers per second (1,864 miles per second).
CMEs are monitored by the Space Weather Prediction Center with the National Oceanic and Atmospheric Administration using a combination of ground- and space-based solar observatories. As noted, space weather is constantly monitored to determine how much damage can be caused to Earth surface power grids and satellite communications. But aside from monitoring space weather, why is it so important to study CMEs?
“CMEs are crucial for the existence of our Sun,” Dr. Salman tells Universe Today. “CMEs appear as a valve that releases the built-up magnetic field from the Sun without which the Sun will rip itself apart. But the investigation of CME science also has important societal relevance. CMEs drive the strongest solar storms that can wreak havoc through impacting power grids and telecommunication networks. CMEs can also damage orbiting satellites and technological infrastructure. CMEs are now counted among the major natural hazards as well. A more in-depth understanding of CMEs (from initiation to propagation to evolution along the Sun-Earth line) is thus required to improve the current status quo of space weather operations.”
What new discoveries will researchers make about coronal mass ejections in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
Reanalysing the partial 1859 Carrington event data a paper has confirmed an 1861 analysis that puts the event as larger than later believed.
““Looking at the rate of change … it’s at least 500 nanotesla per minute, which kind of supports what the original 1861 papers suggested,” Beggan told New Scientist. “It just proves once again that the Carrington storm was an extreme event.”” [Stephen Luntz, IFLScience]
A handful of Carrington magnitude events during the last 8,000 years have been traced in the geological record from radioisotopes, and two of the events were estimated to be an order of magnitude larger [“Carrington event”, Wikipedia].