New Discoveries: The Mysterious Solar Gamma Rays

Excess Solar Gamma Rays Detected by HAWC Collaboration

In a groundbreaking discovery, scientists from the High-Altitude Water Cherenkov Observatory Collaboration (HAWC Collaboration) have detected the most energetic light ever seen emanating from the Sun. This detection of solar gamma radiation in the teraelectronvolt (TeV) range has left solar physicists puzzled, as it did not correlate with any heightened solar activity.

The Sun, being the most intensely studied star in the cosmos, still holds many mysteries. While we have observations spanning the entire spectrum of its emissions, there is still much we don’t know about its processes. Magnetic fields are known to play a crucial role in solar activity, but the mechanisms behind this phenomenon remain poorly understood.

The HAWC observatory, located in Mexico, is one of the tools used by scientists to study gamma and cosmic radiation from space that interacts with Earth’s atmosphere. By detecting high-energy particles produced when this radiation is blocked by the atmosphere, researchers can calculate the energy and direction of the parent gamma rays.

The HAWC Collaboration conducted a 6-year observing campaign from 2014 to 2021, during which they detected emissions ranging between 0.5 and 2.6 TeV coming from the direction of the Sun. This emission was confirmed to be from the Sun with a 6.3 sigma probability.

While this is not the highest energy light ever observed in space, it is a significant discovery for our own star. The excess of gamma rays detected by HAWC has left scientists astounded, as the Sun is not expected to emit such bright light at these energies.

The team believes that the TeV emission is a result of the interaction between galactic cosmic rays and nuclei in the solar atmosphere. Similar to how cosmic rays interact with Earth’s atmosphere to produce a gamma ray glow, it is thought that a similar process occurs on the Sun.

However, the exact mechanism behind the bright emission remains unknown. The current theoretical models do not match the observed data. It is likely that the Sun’s messy magnetic fields play a role in this phenomenon. A recent paper proposed that the solar magnetic fields act as accelerators for cosmic ray electrons, producing synchrotron gamma radiation.

Further modeling and research will be necessary to fully understand this anomalous excess of gamma rays from the Sun. The HAWC Collaboration’s observations highlight the need for a revised framework that can explain the observed gamma-ray flux from the Sun in both the GeV and TeV ranges.

The research conducted by the HAWC Collaboration has been published in the journal Physical Review Letters, marking a significant step forward in our understanding of the Sun’s emissions and the role of magnetic fields in solar activity.

How are the light sensors in Mosphere able to detect gamma rays emitted by cosmic sources?

Mosphere. It consists of a collection of water-filled tanks equipped with light sensors, positioned in the Sierra Negra volcanic range. These sensors are capable of detecting gamma rays, which are high-energy particles emitted by cosmic sources, such as supernovae, pulsars, and black holes.

While the primary focus of HAWC Collaboration is to study cosmic phenomena, the team also keeps a close eye on the Sun. The recent discovery of solar gamma radiation, however, has presented a perplexing puzzle for the scientists. The detection of solar gamma rays in the TeV range suggests that the Sun is producing highly energetic light particles, but without any corresponding increase in solar activity. Solar activity encompasses various phenomena, such as solar flares and coronal mass ejections, which typically produce high-energy emissions.

To further understand this unexpected finding, scientists have turned to existing theories and models. One possibility is that the observed gamma rays are originating from some “hidden” solar activity that current instruments cannot detect. Another possibility is that the gamma rays are being produced by interactions between high-energy cosmic rays and magnetic fields within the Sun’s atmosphere.

“Magnetic fields are known to be involved in solar activity, but the precise mechanisms behind their influence are not well-known,” explained Professor Brenda Dingus, a physicist at Los Alamos National Laboratory and a member of the HAWC Collaboration. “These excess gamma rays could be a clue to better understanding the interplay between magnetic fields and solar phenomena.”

Understanding the Sun’s magnetic fields and their relation to solar activity is not only important for solving this puzzle but also for predicting and preparing for space weather events that can impact Earth. Solar flares and coronal mass ejections can release vast amounts of energy and charged particles, which, if directed towards Earth, can disrupt satellite communication, damage power grids, and pose risks to astronauts in space.

The discovery of excess solar gamma radiation by the HAWC Collaboration provides a deeper insight into the Sun’s intricate processes. As scientists continue to study these observations and delve further into the mysteries of the Sun, new discoveries and breakthroughs are expected. These findings not only contribute to our knowledge of the star at the center of our solar system but also hold implications for understanding other cosmic phenomena in the universe.