For decades, scientists have been attempting to solve a perplexing problem concerning the weather in outer space: At unpredictable times, high-energy particles bombard the Earth and objects outside the Earth's atmosphere with radiation, endangering astronauts' lives and destroying satellites' electronic equipment. These flare-ups can even produce radiation showers powerful enough to reach passengers in planes flying over the North Pole. Despite the greatest efforts of experts, a clear pattern of how and when flare-ups will occur has remained elusive.
In a paper published this week in The Astrophysical Journal Letters, authors Luca Comisso and Lorenzo Sironi of Columbia University's Department of Astronomy and the Astrophysics Laboratory used supercomputers to simulate when and how high-energy particles are born in turbulent environments such as the sun's atmosphere. This new study opens the door to more precise forecasts of when harmful bursts of these particles may occur.
This fascinating new discovery, according to Comisso, will help us to better anticipate the origin of solar energetic particles and enhance forecasting models of space weather events, which is a primary aim of NASA and other space organizations and governments worldwide. NASA's Parker Solar Probe, the nearest spacecraft to the sun, may be able to corroborate the paper's conclusions in the coming years by directly witnessing the expected distribution of high-energy particles created in the sun's outer atmosphere.
Comisso and Sironi show in their study "Ion and Electron Acceleration in Fully Kinetic Plasma Turbulence," that magnetic fields in the sun's outer atmosphere may accelerate ions and electrons to near-light speeds. The outer atmosphere of the sun and other stars is made up of particles in a plasma state, which is a highly turbulent state separate from liquid, gas, and solid states. Scientists have long thought that high-energy particles are produced by the sun's plasma. However, particles in the plasma move so irregularly and unpredictably that they have yet to clearly illustrate how and when this occurs.
Comisso and Sironi produced computer models of the exact motions of electrons and ions in the sun's plasma using supercomputers at Columbia, NASA, and the National Energy Research Scientific Computing Center. These models match the sun's atmosphere conditions and give the most comprehensive data on how and when high-energy particles develop to date.
The findings resolve concerns that scientists have been pondering for at least 70 years: In 1949, physicist Enrico Fermi began exploring magnetic fields in outer space as a possible source of high-energy particles (dubbed cosmic rays) detected entering the Earth's atmosphere. Scientists have assumed that the sun's plasma is a key source of these particles since then, but establishing it definitely has been challenging.
Comisso and Sironi's discovery, which was funded by NASA and the National Science Foundation, has far-reaching consequences outside our solar system. The vast majority of visible matter in the cosmos is in the form of plasma. Understanding how some of the particles that make up plasma can be accelerated to high energies is an important new research area because energetic particles are routinely observed not only around the sun but also in other environments throughout the universe, such as the surroundings of black holes and neutron stars.
While the current work by Comisso and Sironi focuses on the sun, more simulations might be done in various scenarios to understand how and when distant stars, black holes, and other things in the universe will release their own bursts of energy.
Our findings are centered on the sun, but they may also be viewed as a beginning point for better understanding how high-energy particles are formed in more distant stars and surrounding black holes, according to Comisso. We've merely scratched the surface of what supercomputer simulations can teach us about the birth of these particles throughout the cosmos.
Journal Information: Ion and Electron Acceleration in Fully Kinetic Plasma Turbulence, The Astrophysical Journal Letters (2022). iopscience.iop.org/article/10. … 847/2041-8213/ac8422