Exploring How Charged Particles Accelerate and Escape the Sun's Influence

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Exploring How Charged Particles Accelerate and Escape the Sun's Influence

Asked by terryaster at 1:17pm on Jan 21 2025

The sun, a blazing sphere of hydrogen and helium, exhibits surface and atmospheric temperatures ranging from 10,000 to 3.6 million degrees Fahrenheit. This immense heat drives the continuous emission of solar wind—streams of plasma made up of charged particles, including protons and electrons, that escape the sun’s gravity and flow into space. Understanding how these particles interact with energetic solar eruptions provides valuable insights into phenomena like cosmic rays from supernova explosions.

Thomas Do, a graduate astronomy student at Michigan State University, has developed a model predicting how particles accelerate under broader conditions than previously understood. His research, which builds on earlier models, may also enhance our understanding of solar storms and their potential impact on space technologies.

Do’s interest in charged particle acceleration began during his undergraduate research at the Harvard-Smithsonian Center for Astrophysics. He explored how particles gain energy when swept along by coronal mass ejections (CMEs)—massive explosions from the sun’s surface that create shock waves when sufficiently fast.

"As these ejections travel from the sun, they interact with charged particles, transferring energy via the shock wave," Do explained. This energy transfer accelerates particles, propelling them through space toward Earth. Occasionally, particles gain enough speed to escape the shock wave entirely, hurtling into the cosmos.

To improve predictions of particle behavior, Do refined a 2021 model by astrophysicist Federico Fraschetti. Their updated model expands on earlier work by considering how particles of varying energy levels accelerate and escape from the shock wave region. This marks a significant departure from previous models, which only accounted for high-energy particles. By incorporating multiple energy levels, the new equations offer a more realistic depiction of particle acceleration over time and the likelihood of escape at different energy levels.

"We aim to allow for more particles to escape because it reflects what happens in reality," Do said.

The researchers tested their model against data from a real solar event. On September 5, 2022, the sun unleashed a powerful burst of energy, coinciding with a close flyby of NASA’s Parker Solar Probe. The probe, designed to study the sun’s outer regions, recorded key data, including particle speeds and temperatures, as the shock wave collided with it.

"The timing was incredibly fortunate," Fraschetti noted. "This is exactly the type of event the Parker Solar Probe was built to observe."

The probe’s data confirmed the model’s predictions, showing particle acceleration and escape across a range of energy levels. Given the probe’s proximity to the sun—equivalent to just 7 centimeters away if the Earth-sun distance were scaled to one meter—it captured particles shortly after they interacted with the shock wave. This allowed the team to analyze early stages of particle acceleration.

"The results aligned perfectly with our model, validating our physical understanding of shock waves close to the sun," Fraschetti said. "This was the first time this expectation had been tested, and the outcome was far from guaranteed."

Do highlighted that the model’s applications extend beyond solar physics. "This framework can be applied to other space phenomena involving charged particles," he said, potentially advancing research into cosmic rays and other astrophysical events.

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