The Sun, an immense and powerful sphere of gas, is the driving force behind many phenomena that impact our solar system, including the behavior of charged particles in space. At its core, the Sun’s temperatures soar to millions of degrees, and its outer atmosphere, the corona, reaches extreme temperatures of up to 3.6 million degrees Fahrenheit. This immense heat results in the continuous expulsion of plasma, a charged mixture of subatomic particles, primarily protons and electrons. These particles, propelled by intense energy from the Sun, escape its gravitational pull and form the solar wind, traveling outward into the cosmos.
Solar wind plays a significant role in shaping the environment of space, with important implications for space-based technologies and Earth’s climate. One of the critical factors in understanding the solar wind involves understanding the dynamics of charged particles, especially their acceleration and interaction with the Sun’s eruptions of energy, such as solar flares and coronal mass ejections (CMEs). These energetic interactions provide scientists valuable insights into other cosmic phenomena, such as cosmic rays produced in supernova explosions.
In a recent breakthrough, Thomas Do, an astronomy graduate student at Michigan State University, contributed significantly to the understanding of these processes. By expanding on earlier models, Do developed new theoretical models that could explain how charged particles accelerate under a broader range of circumstances. These models, crucial for forecasting the impact of solar storms on space-based technology, mark a major advancement in our knowledge of the Sun’s effect on space weather.
The Sun’s Eruptions and Their Role in Particle Acceleration
The Sun regularly experiences bursts of energy in the form of solar flares and CMEs. These powerful events expel massive amounts of plasma and radiation into space. While many of these eruptions impact space and terrestrial conditions, scientists were keen to understand how charged particles from these solar eruptions accelerate to such extreme velocities, especially considering the complex interplay between shock waves and particles.
During his undergraduate research at the Harvard-Smithsonian Center for Astrophysics in Massachusetts, Do began his journey into understanding how particles accelerate within solar phenomena. His work focused particularly on the powerful ejections of solar mass—CMEs—which when accelerated at high speeds, create shock waves traveling away from the Sun. These shock waves can have a significant impact on particles within the path of these ejections.
“As these eruptions travel away from the Sun, they collide with the particles in the solar wind. During these collisions, the particles gain energy from the shock waves,” Do explained.
The process of particle acceleration takes place as the particles interact with these shock waves. In some instances, the particles gain enough velocity to escape the shock front entirely and continue their journey into space. At its most extreme, the particles may accelerate so rapidly that they break free from the outer boundaries of the solar system.
Expanding Our Understanding of Particle Behavior
Previous models of particle acceleration focused primarily on high-energy particles that gain speed from shock waves. These early models, developed several decades ago, did not account for particles with lower energy levels. Thus, only particles that already had significant energy were considered capable of escaping the Sun’s magnetic influence. This assumption limited the ability to fully predict the behavior of solar particles.
In 2021, Federico Fraschetti, an astrophysicist at the Center for Astrophysics, and Thomas Do collaborated to refine the existing model by including low-energy particles. Their work involved developing a more comprehensive approach that allows scientists to account for a greater variety of particle energies, both high and low, when considering particle acceleration.
“We wanted to ensure our model was more physically realistic by allowing more particles to escape,” Do stated. By adjusting the models, Do and Fraschetti created a set of equations capable of predicting how particles at various energy levels will accelerate over time, and how many will eventually escape into space.
The major advantage of the new model was its ability to predict not just how high-energy particles behaved during solar events, but also how lower-energy particles gained speed. Previously, it was thought that only the high-energy particles gained enough energy to escape the shock waves of solar events, but this model provides a more accurate and holistic prediction.
The Sun’s Solar Cycle and Solar Maximum
Every 11 years, the Sun reaches a period known as solar maximum, which marks the peak of the Sun’s 11-year cycle of solar activity. During this time, the Sun experiences the highest level of solar activity, and phenomena such as coronal mass ejections become much more frequent and intense. This cyclical variation in solar activity influences space weather and plays a crucial role in the acceleration of charged particles.
At the solar maximum, the likelihood of significant solar eruptions increases, meaning more shock waves that accelerate particles are generated. As the frequency and intensity of solar events increase, researchers like Do and Fraschetti knew they would eventually have a chance to test their models against a real solar event.
The Solar Event of September 2022: A Landmark Experiment
In September 2022, just as the Sun was reaching its solar maximum, the solar system’s most advanced spacecraft, NASA’s Parker Solar Probe, was on a close encounter with the Sun. The probe was designed specifically to observe solar phenomena firsthand, capturing real-time data as it passed through the intense space weather surrounding our star.
On September 5, 2022, a large CME erupted from the Sun, sending a huge burst of energy and charged particles into space. The Parker Solar Probe, which was remarkably close to the Sun at that moment, recorded essential data regarding the speed and temperature of the solar particles as the shock wave from the eruption impacted the probe.
“We were fortunate to see the very beginning of this process during the solar flare in September 2022,” Fraschetti noted. “This was exactly what the Parker Solar Probe was designed to observe.”
This rare alignment allowed the team to validate their new model under actual solar conditions. The data collected by the probe matched the predictions made by the updated model, confirming that particles from the CME accelerated across a range of energies, as the model had forecast.
The close proximity of the Parker Solar Probe to the Sun during this event was instrumental in gathering accurate data. To put it in perspective, if the distance between the Earth and the Sun were scaled down to just one meter, the probe would have been a mere 7 centimeters away. This proximity enabled the team to measure the particles’ behavior right after they interacted with the shock wave, providing crucial insights into how particles accelerated at the initial stages.
“The agreement between our model and the data from the Parker Solar Probe was remarkable,” Fraschetti said. “It confirmed that our expectations about what happens to particles near young shock waves close to the Sun were accurate. This was a crucial test that had never been done before.”
Implications and Future Research
The successful validation of the expanded model has important implications for multiple areas of space research. Not only does it advance our understanding of solar phenomena and the behavior of charged particles, but it also opens the door to better predictions of solar storms’ impact on space-based technologies. By applying these refined models, scientists can more accurately predict when solar particles may pose a risk to satellites, spacecraft, or even power grids here on Earth.
“We now have a tool that can predict how charged particles from various sources behave and accelerate, from the Sun to cosmic events like supernova explosions,” Do explained. This understanding can lead to more informed decisions when it comes to protecting critical space infrastructure or monitoring future solar activity.
Furthermore, Do’s work and his collaboration with Fraschetti represent an important milestone in the study of space weather and particle acceleration. As we learn more about these dynamics, it can offer crucial insights into the broader behavior of energetic particles across the universe, from other star systems to the cosmic environments formed by exploding stars.
In the coming years, as solar activity intensifies and our tools and models improve, the ability to predict the behavior of charged particles with greater precision will be crucial for space exploration, our technological infrastructure, and our understanding of the universe at large.
Conclusion
The study of charged particles and their interactions with solar phenomena, particularly solar flares and coronal mass ejections (CMEs), represents a critical area of research in understanding space weather and its potential impacts on space-based technology. Through the work of Thomas Do and Federico Fraschetti, our understanding of particle acceleration has taken a significant leap forward. By expanding on previous models to account for both high-energy and low-energy particles, they have developed a more accurate and physically realistic framework that can predict how particles are affected by shock waves from solar eruptions.
The groundbreaking success of their model, validated by real-world data from NASA’s Parker Solar Probe, confirms the validity of these predictions and opens the door to improved forecasting of solar events and their effects on space systems. As the Sun reaches its solar maximum, these insights will prove crucial in predicting the frequency, intensity, and behavior of solar eruptions, helping to protect critical space infrastructure and improve our ability to navigate through cosmic phenomena.
Furthermore, the refined model holds the potential for broader applications, from predicting particle behavior in space to understanding cosmic rays produced by supernovae. This research marks an important step toward not only protecting our technological assets in space but also enhancing our ability to study the behavior of particles across the universe, from our Sun to distant stars.
As solar research continues to evolve and our technological capabilities advance, the ability to predict the movement and acceleration of charged particles will have lasting impacts on science and technology. By unraveling the complex interactions that shape the behavior of particles in space, scientists like Do and Fraschetti are deepening our understanding of the universe, providing valuable insights that are crucial for the safety, advancement, and progress of space exploration and technology in the years ahead.
Reference: Thomas M. Do et al, Time-dependent Acceleration and Escape of Charged Particles at Traveling Shocks in the Near-Sun Environment, The Astrophysical Journal (2025). DOI: 10.3847/1538-4357/ad93b2