New research by a team led by UC San Diego astrophysics graduate student Aravind Bharathi Valluvan has discovered a significant number of slow-building solar flares, which could change our understanding of these phenomena.
Solar flares occur when magnetic energy builds up in the Sun’s atmosphere and is released as electromagnetic radiation. They can last from a few minutes to a few hours and reach temperatures of around 10 million degrees Kelvin. Due to their intense electromagnetic energy, solar flares can cause disruptions in radio communications, Earth-orbiting satellites, and even result in blackouts.
In a new paper in Solar Physics, the team explains that solar flares have been classified based on the amount of energy they emit at their peak. However, there has not been significant study into differentiating flares based on the speed of energy build-up since slow-building flares were first discovered in the 1980s.
Using the increased capabilities of the Chandrayaan-2 solar orbiter, researchers from the Indian Institute of Technology Bombay (IITB) used the first three years of observed data to catalog nearly 1400 slow-rising flares — a dramatic increase over the roughly 100 that had been previously observed over the past four decades.
The width-to-decay ratio of a flare is the time it takes to reach maximum intensity to the time it takes to dissipate its energy. Most commonly, flares spend more time dissipating than rising. In a 5-minute flare, it may take 1 minute to rise and 4 minutes to dissipate for a ratio of 1:4. In slow-building flares, that ratio may be 1:1, with 2.5 minutes to rise and 2.5 minutes to dissipate.
According to Valluvan, seeing slow-building flares in such high quantities may change the thinking that solar flares were like the snap of a whip, quickly injecting energy before slowly dissipating. The team identified two different types of flares but believes there may be more.
“There is thrilling work to be done here. We’ve identified two different types of flares, but there may be more. And where do the processes differ? What makes them rise and fall at different rates? This is something we need to understand,” said Valluvan, who now works in UC San Diego Professor of Astronomy and Astrophysics Steven Boggs’ group.
Understanding more about the speed of energy build-up in solar flares could help us better predict and prepare for the disruptions that they can cause.
Journal Reference
- Valluvan, A.B., Goyal, A., Jain, D. et al. Solar Flare Catalogue from 3 Years of Chandrayaan-2 XSM Observations. Solar Physics 299, 8 (2024). DOI: 10.1007/s11207-023-02244-0