Posted on Categories Discover Magazine
As March was drawing to a close, a powerful solar flare exploded from the Sun, causing X-rays and ultraviolet radiation to rocket toward Earth. Peaking at 10:33 p.m. Eastern Time on March 28, 2023, the flare was of the strongest kind — an X-class flare, according to NOAA’s Space Weather Prediction Center.
Traveling at the speed of light, the radiation reached Earth almost immediately, causing ionization in parts of the upper atmosphere on the sunlit side. This, in turn, triggered a blackout of some radio communications for about an hour in Southeast Asia, Australia and New Zealand.
The strongest flares release energy equivalent to millions of 100-megaton hydrogen bombs exploding at the same time, or about one tenth of the total energy emitted by the entire Sun in one second.
Flares typically explode from active regions on the Sun. These areas are laced with strong magnetic fields associated with groups of sunspots. As the magnetic fields evolve, they can become unstable and suddenly flare with massive amounts of energy.
NASA’s Solar Dynamics Observatory, which watches the Sun constantly, captured the image above of the latest solar flare. Here is an animation showing the flare:
In this animation of Solar Dynamics Observatory images, the solar flare is visible as a bright flash on the bottom right of the Sun. (Credit: NASA/SDO)
And here’s another animation, viewing the Sun in a different wavelength of light and cropped in tightly:
A closer view of the solar flare. (Credit: NASA/SDO)
As the electrically charged gas that makes up the Sun moves, it generates powerful magnetic fields. These fields are constantly in flux, and over the course of about 11 years they go through a cycle, known as the solar cycle.
At the peak of solar activity, sunspots are most numerous, and flares and ejections of material from the Sun are at their maximum. At this time, the polarity of the Sun’s overall magnetic field reverses. This means that the Sun’s north and south magnetic poles switch places.
The observed and predicted solar cycle is depicted here, in the form of sunspot numbers. The mean forecast for the current solar cycle (Cycle 25) is given by the red line. As indicated by the black line, activity has already climbed higher than the predicted peak in 2025. (Credit: NOAA Space Weather Prediction Center)
According to the latest forecast, this cycle’s peak of solar activity should occur in July of 2025. But activity during this cycle is already exceeding expectations. After bottoming out in 2020, it has ramped up much more vigorously than predicted, and in January it actually reached a higher level than the peak forecast for 2025.