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The Sun in gamma rays over a 14-year period captured on video

Scientists have unveiled new insights into the Sun’s gamma-ray emissions, producing a fourteen-year movie of the Sun in gamma rays.

This fascinating new study was spearheaded by Bruno Arsioli from the Institute of Astrophysics and Space Sciences (IA) and the Faculty of Sciences of the University of Lisbon (Ciências ULisboa) in Portugal.

Their research marks a significant advancement in our understanding of the Sun, particularly its polar regions, which were observed to emit high-energy radiation more actively than expected during the previous solar maximum.

Enigma of the Sun’s gamma rays

The Sun, while radiantly shining in visible light, harbors a much more formidable aspect when viewed in the highest energies of electromagnetic radiation, such as gamma rays.

“The Sun is stormed with close to light-speed particles coming from beyond our galaxy in all directions,” says Arsioli.

These gamma rays, invisible to the naked eye and blocked by Earth’s atmosphere, carry a billion times more energy than ultraviolet light.

“These so-called cosmic rays are electrically charged and are deflected by the Sun’s magnetic fields. Those that interact with the solar atmosphere produce a shower of gamma rays,” Arsioli explained. 

Understanding the Sun’s gamma-ray emissions is crucial for predicting space weather that affects satellite operations and terrestrial communications.

14-years of the Sun’s gamma rays

Arsioli’s study, produced a fourteen-year compressed movie of the Sun in gamma rays.

A meticulous analysis of these observations, made by the Fermi Large Area Telescope (Fermi-LAT), reveals an unexpected brightness in the Sun’s polar regions in gamma rays.

This phenomenon was particularly pronounced in June 2014, during the peak of solar activity and coinciding with the reversal of the solar magnetic field.

“We have found results that challenge our current understanding of the Sun and its environment,” says Orlando.

“We demonstrated a strong correlation of the asymmetry in the solar gamma-ray emission in coincidence with the solar magnetic field flip, which has revealed a possible link among solar astronomy, particle physics, and plasma physics,” she concluded.

This discovery challenges the previously held belief that gamma-ray emissions would be uniformly distributed across the Sun’s surface.

Bridging solar astronomy and particle physics

The research highlights a peculiar asymmetry in the energy of gamma rays emitted from the Sun’s poles, with the south pole emitting photons of higher energy compared to the north pole.

This asymmetry, along with the unexpected concentration of gamma rays at higher latitudes, suggests a complex interaction between cosmic rays, the Sun’s magnetic field, and its atmosphere, which remains not fully understood.

Elena Orlando, co-author of the study and a researcher at the University of Trieste, INFN, and Stanford University, emphasizes the significance of these findings.

The correlation between the asymmetry in solar gamma-ray emission and the solar magnetic field flip suggests a potential link between solar astronomy, particle physics, and plasma physics.

This opens new avenues for theoretical models that could explain the observed phenomena and improve predictions of solar activity.

The study utilized a novel visualization tool, integrating solar gamma-ray events over periods of 400 to 700 days, which clarified the moments of polar excesses and the energy discrepancy between the north and south poles.

This approach not only sheds light on the processes generating these gamma-ray excesses at the poles but also underscores the role of cosmic rays as probes of the inner solar atmosphere.

Looking ahead: The next solar maximum

As the Sun approaches a new solar maximum, with another magnetic pole inversion underway, Arsioli and Orlando anticipate further research to assess if this event is followed by an increase in gamma-ray emissions from the poles.

“In 2024 and the next year we will experience a new solar maximum, and another inversion of the Sun’s magnetic poles has already started. We expect by the end of 2025 to reassess if the inversion of the magnetic fields is followed by a surplus in the gamma rays emissions from the poles,” says Bruno Arsioli.

Elena Orlando adds, “We have found the key to unlock this mystery, which suggests the future directions that should be taken. It is fundamental that the Fermi telescope will operate and observe the Sun in the coming years.”

Their findings underscore the importance of continuous monitoring of the Sun by current and future gamma-ray space observatories to enhance our understanding of solar activity and its impact on space weather forecasts.

Implications and future research

In summary, this important study has profoundly shifted our understanding of the Sun, particularly its polar regions’ unexpected gamma-ray emissions.

By analyzing 14 years of data from the Fermi Large Area Telescope, the team revealed that the Sun’s poles emit gamma rays more actively than previously thought, especially during periods of intense solar activity.

This discovery, highlighting an asymmetry in energy emissions between the poles and the correlation with the solar magnetic field’s reversal, challenges existing theories and opens new pathways for future research.

As we approach another solar maximum, this work sets the stage for further investigations that could refine our models of solar activity and enhance space weather forecasting, underscoring the importance of continuous monitoring and study of our star’s most energetic phenomena.

The full study was published in The Astrophysical Journal.


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