Is the Sun waking up? Biggest solar flare spotted since 2017 may be a sign of change in solar cycle
After a very quiet period of over 900 days, the Sun might be waking up. On May 29, dark spots that freckle the face of the sun, representing areas of complex magnetic fields, sported the biggest solar flare since October 2017. While sunspots are not yet visible and will soon rotate into view over the left limb of the sun, flares were spotted by NASA's sun-watching Solar Dynamics Observatory (SDO).
According to NASA, it was the first M-class flare since October 2017, and scientists will be watching to see if the Sun is beginning to wake up. “On May 29, at 3.24 am EST, a relatively small M-class solar flare blazed from the sunspots. The flares were too weak to pass the threshold at which the National Oceanic and Atmospheric Administration or NOAA's Space Weather Prediction Center provide alerts. But after several months of very few sunspots and little solar activity, scientists and space weather forecasters are keeping their eye on this new cluster to see whether they grow or quickly disappear. The sunspots may well be harbingers of the sun's solar cycle ramping up and becoming more active. Or, they may not. It will be a few more months before we know for sure,” said NASA.
Sunspots are areas that appear dark because they are cooler than other parts of the sun’s surface. Solar flares are an explosion of energy that occur when magnetic lines near sunspots tangle, cross and reorganize. Space weather scientists classify flares based on their intensity, with X-class flares being the most powerful. Harmful radiation from a flare cannot pass through Earth's atmosphere to physically affect humans on the ground. However, when intense enough, they can disturb the atmosphere in the layer where GPS and communications signals travel. The intensity of the current flare was below the threshold that could affect geomagnetic space.
The sun’s activity varies over an 11-year cycle, during which the number of sunspots and the amount of solar flare activity changes. Every 11 years or so, sunspots fade away, bringing a period of relative calm, called the “solar minimum.” In February 2020, NASA’s Solar Dynamics Observatory celebrated its 10th year in space. According to scientists, with a decade of observations, SDO has now seen nearly a complete 11-year solar cycle. These multi-year observations help scientists understand signs that signal the decline of one solar cycle and the onset of the next. Scientists from NASA and NOAA track sunspots to determine, and predict, the progress of the solar cycle, and ultimately, solar activity. The sun is currently thought to be in a period of minimal activity, that is, solar minimum. Scientists peg the start of new cycles at solar minimum, and the appearance of this solar flare could indicate the end of the current solar cycle, called Solar Cycle 24 and the beginning of Solar Cycle 25.
“Currently, scientists are paying close attention to the sunspot number as it's key to determining the dates of solar minimum, which is the official start of Solar Cycle 25. This new sunspot activity could be a sign that the sun is possibly revving up to the new cycle and has passed through minimum,” say experts.
However, it takes at least six months of solar observations and sunspot-counting after a minimum to know when it has taken place. Since that minimum is defined by the lowest number of sunspots in a cycle, scientists need to see the numbers consistently rising before they can determine when exactly they were at the bottom. According to scientists, this implies that “solar minimum is an instance only recognizable in hindsight: it could take six to 12 months after the fact to confirm when the minimum has actually passed.” They explain that one reason behind this is that the sun is extremely variable. Just because the sunspot numbers go up or down in a given month does not mean it will not reverse course the next month, only to go back again the month after that. Hence, scientists need long-term data to build a picture of the Sun’s overall trends through the solar cycle.
Over the past decade, SDO has kept a constant eye on the sun, studying how the sun creates solar activity and drives space weather — the dynamic conditions in space that impact the entire solar system, including Earth. In its first year-and-a-half itself, the spacecraft saw nearly 200 solar flares, which allowed scientists to spot a pattern. They noticed that around 15% of the flares had a “late phase flare” that would follow minutes to hours after the initial flare. By studying this special class, scientists gained a better understanding of just how much energy is produced when the sun erupts.