by Erica Marchand
Lisbon, Portugal (SPX) Feb 08, 2024
In a groundbreaking study published in *The Astrophysical Journal*, researchers have unveiled unexpected findings regarding the Sun's gamma-ray emissions, particularly during periods of heightened solar activity known as the solar maximum. This research, spearheaded by Bruno Arsioli from the Institute of Astrophysics and Space Sciences (IA) and the Faculty of Sciences of the University of Lisbon (Ciencias ULisboa), in collaboration with Elena Orlando from the University of Trieste, INFN, and Stanford University, provides new insights into the high-energy processes occurring in our star's atmosphere.
Gamma rays, the highest energy form of electromagnetic radiation, are produced by various processes in the Sun, including in its halo and during solar flares. These rays carry a billion times more energy than ultraviolet light and are a key to understanding violent events on the Sun's surface. The study's findings challenge the previously held belief that gamma rays emitted from the Sun would show a uniform distribution across the solar disk.
Utilizing 14 years of data from the Fermi Large Area Telescope (Fermi-LAT), covering a full solar cycle from August 2008 to January 2022, the researchers developed a visualization tool that compresses this period into a movie. This innovative approach revealed that gamma-ray emissions are not uniformly distributed as previously thought. Instead, there's a pronounced brightness in the polar regions of the solar disk, especially noticeable during the peak of solar activity in June 2014.
"The Sun is bombarded with cosmic rays, charged particles that are deflected by the Sun's magnetic fields. When these cosmic rays interact with the solar atmosphere, they produce gamma rays," explains Bruno Arsioli. This interaction suggests that cosmic rays might be influencing the Sun's magnetic field differently across latitudes, leading to the observed asymmetry in gamma-ray emissions.
A particularly intriguing aspect of this study is the detection of an energy difference between the poles, with the south pole showing emissions of higher energy photons compared to the north. This asymmetry remains unexplained and poses a challenge to current solar physics models.
The correlation between these gamma-ray emissions and the solar magnetic field flip, a phenomenon occurring once every eleven years at the peak of solar activity, suggests a deeper connection between solar astronomy, particle physics, and plasma physics. This link is crucial for improving our understanding of the Sun and enhancing the accuracy of space weather forecasts, which are vital for protecting satellites and terrestrial electronic infrastructures.
Looking ahead, the research team anticipates the upcoming solar maximum in 2024 and 2025, with another inversion of the Sun's magnetic poles already underway. "We expect to reassess if the inversion of the magnetic fields is followed by a surplus in the gamma rays emissions from the poles," says Arsioli. This forward-looking perspective underscores the importance of continuous monitoring by current and future gamma-ray space observatories to provide real-time data on solar activity.
The implications of this study extend beyond the immediate findings. By demonstrating the potential for gamma-ray emissions to carry information about solar activity, the researchers have made a compelling case for the planning of future missions focused on solar observation. As Arsioli notes, understanding the processes behind these emissions could open new avenues for investigating the solar atmosphere and improve the models predicting solar activity.
This research not only challenges our current understanding of the Sun but also sets the stage for future explorations into the mysteries of our star. The continuous monitoring and analysis of the Sun by gamma-ray observatories promise to unveil further secrets and enhance our ability to predict and mitigate the impacts of solar activity on our technology-dependent world.
This study represents a significant step forward in solar physics, providing valuable insights into the complex dynamics of our star and highlighting the need for ongoing observation and theoretical development in the field.