New Research Indicates the Sun may be More Prone to Flares Than We Thought
This past year saw some significant solar activity. This was especially true during the month of May, which saw more than 350 solar storms, solar flares, and geomagnetic storms. This included the strongest solar storm in 20 years that produced aurorae at far lower latitudes than usual and the strongest solar flare observed since December 2019. Given the threat they pose to radio communications, power grids, navigation systems, and spacecraft and astronauts, numerous agencies actively monitor the Sun's behavior to learn more about its long-term activity.
However, astronomers have not yet determined whether the Sun can produce “superflares” or how often they might occur. While indicators such as tree rings and samples of millennia-old glacial ice effectively record the most powerful superflares, they are not effective for determining the frequency of these events. Direct measurements of solar activity, available since the Space Age, reaffirm the challenge of quantifying these phenomena. A recent study employed a novel methodology, analyzing Kepler data on tens of thousands of sun-like stars to estimate the frequency of superflares produced by stars similar to our sun.
The study was conducted by the Max Planck Institute for Solar System Research (MPS), the Sodankylä Geophysical Observatory (SGO), and the Space Physics and Astronomy Research Unit at the University of Oulu, along with various other prominent institutions including the National Astronomical Observatory of Japan (NAOJ), the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado Boulder, the National Solar Observatory (NSO), and the Commissariat of Atomic and Alternative Energies. The resulting research was recently published in the journal Science.
Understanding Superflares
Superflares are remarkable for their intense radiation emission, reaching about 1032 erg, or 6.24 x 10³⁵ Joules. To provide some context, during the Carrington Event of 1859 (one of the most violent solar storms recorded in the last two centuries), the energy released was only a fraction—approximately one hundredth—of a superflare’s energy.
The historical records of powerful solar events were utilized, including tree rings and glacial samples that effectively chronicle these extreme incidents. Yet with the Kepler Space Telescope's observations, the astronomical community has learned that monitoring thousands of stars supplant traditional methods and grant a better understanding of the rate at which such violent solar events occur.
Data from the Kepler Space Telescope
The Kepler Space Telescope continuously observed around 100,000 main-sequence stars, searching for dimming patterns that suggest the presence of exoplanets. These observations yielded a plethora of solar flares, which were captured as sharp peaks in brightness within the collected data.
“We cannot observe the Sun over thousands of years. However, we can monitor the behavior of thousands of stars very similar to the Sun over short periods of time. This helps us to estimate how frequently superflares occur.” – Prof. Dr. Sami Solanki, Director at MPS and a co-author of the research paper.
The Methodology of the Study
Through rigorous data analysis, the research team scrutinized Kepler data collected from 56,450 sun-like stars between 2009 and 2013. This analysis included detecting potential superflares that were represented as mere pixels in the images. Researchers selected stars with surface temperatures and brightness akin to the Sun's and duly eliminated several potential sources of error, including cosmic radiation and other transient phenomena.
Altogether, the Kepler data pooled significant evidence of approximately 220,000 years of stellar activity, during which the team identified 2,889 superflares across 2,527 of the observed stars, yielding an average of one superflare per star every century.
Historical Superflare Frequencies
Prior studies deduced that solar superflares may occur every thousand to ten thousand years, primarily based on indirect evidence. High levels of energized particles reaching Earth's atmosphere in prior periods produce measureable amounts of radioactive carbon-14 (C14), a marker allowing astronomers to ascertain historical dominant solar events.
| Study Aspect | Historical Findings | Current Findings |
|---|---|---|
| Average Frequency of Superflares | Every 1,000 - 10,000 years | Every 100 years |
| Data Foundation | Indirect evidence (tree rings, C14) | Direct observations (Kepler data) |
| Total Observed Superflares | Not specified | 2,889 |
However, the studies' existing data and methods suggest that more extreme solar particle events occurred dominantly in the past, raising further questions. The correlation between gigantic flares and coronal mass ejections on a substantial scale is still not fully understood.
Implications of Findings
While this new study reinforces the understanding of solar superflares' frequency and intensity, it emphasizes the need for reliable forecasting and warnings that could mitigate potential impacts on human activities and technologies. An example of these preparations includes the upcoming ESA's Vigil probe, expected to start operation around 2031, which will enhance satellite monitoring of solar activity.
Conclusion and Future Directions
The results of this study herald an insightful shift in the study of solar events, demonstrating the necessity of continuous monitoring and advanced warning systems. With the emergence of new technologies and subsequent learning, the astronomical community looks forward to enhancing their strategies to forecast the Sun's behavior effectively.
For More Information
Authors and researchers involved in this study encourage readers interested in the solar phenomena to explore the following references:
