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On September 6, the sun let its presence be felt by unleashing two massive solar flares. The first eruption, classified as an X2.2 flare, the strongest since 2008, occurred at 5:10 a.m. ET. Shortly after, at 8:02 a.m ET, the star spewed out a bigger, and more dramatic, X9.3 flare — the strongest on record since December 2006.
Solar flares, or storms, begin with an explosion usually above a sunspot, the area where strong magnetic fields poke through the sun's surface. When these spots become unstable, they erupt, releasing significant amounts of energy. Solar flares are classified into one of five categories — A, B, C, M, or X — with each letter indicating an explosion that is ten times stronger than the previous one. The most powerful X flares are capable of producing as much energy as a billion hydrogen bombs. There is also gradation within each category. For example, the X9 flare was seven times more intense than the X2 flare.
Both flares emanated from active region AR 2673. Measuring seven Earth’s wide by nine Earth’s tall, it is the smaller of two massive sunspots off the sun’s surface that are currently active. However, it appears to be the more unstable one, releasing numerous solar flares since it was first identified on August 29.
Though the fierce bursts of radiation are harmful, they are blocked by the Earth’s atmosphere and, therefore, unable to affect humans or animals on the ground. However, the coronal mass ejections (CME) — clouds of protons and other charged particles — that follow the flares within about 20 minutes can disrupt our satellite systems, GPS tracking devices, and power grids. According to the National Oceanic and Atmospheric Administration (NOAA), the September 6 CMEs were powerful enough to black out both high-frequency radio waves and low-frequency communication used in navigation, for about an hour, on the sunlit side of Earth.
However, the slight inconvenience is well worth it, given that when the electrically-charged particles enter the earth’s atmosphere and collide with gases like oxygen and nitrogen, they spark auroras. The incredible light shows are typically observed closer to the northern and southern hemisphere poles because the Earth’s magnetic field attracts the particles toward them. However, the recent powerful CMEs lit up the skies across northern latitudes and could be seen all the way from Finland and Scotland in Europe to Kansas and Ohio in the US.
The occurrence of the flares just as we are moving into a solar minimum, the quietest period of the sun’s 11-year periodic activity cycle, is causing some concern. However, scientists say the eruptions, are just a part of our star’s activity. Besides, AR 2673, which fired off a final X8.2-class flare on September 10, is now away from the Earth-facing side as part of the sun’s normal rotation, and hence, will be unable to send more explosions our way.
Resources: NASA.gov, space.com, aurora-service.eu