Free Astronomy Magazine July-August 2024

JULY-AUGUST 2024 type are not easily avoidable, both because CMEs are unpredictable and because, on average, just 15−18 hours pass between when they are triggered and when the plasma lecular oxygen in green, and atomic oxygen in red. For a CME to result in particularly large auroras, it must originate from a very powerful, typically X-class, solar flare. But this itself is not enough, as the plasma flow must also propagate exactly in the direc- tion of the Earth – an intuitively rare occurrence given the size of the Sun and our distance from it. Close to the peaks of solar activity (the max- imum of this 25 th recorded cycle is expected for next year), CMEs di- rected towards Earth become far more likely due simply to the overall increase in the number of solar flares being produced. When the minimum requirements are met and a geomagnetic storm is unleashed, the fascinating auroras distract (non-experts) from their potential dangers, which include the potential for significant damage to our tech- nologies and our daily activities. For example, the event of May 10 th had a heavy impact on communications, air traffic, satellite operations, and countless activi- ties dependent on global posi- tioning systems (GPSs). Just over two years earlier, in March 2022, a much less violent solar storm led to the destruction of 40 of the 49 Starlink satellites launched into low orbit one day before the solar plasma inter- acted with Earth’s a t m o s p h e r e , causing it to swell and slow down the motion of SpaceX satellites. Problems of this F rom May 3 to May 9, 2024, NASA’s Solar Dynamics Observatory recorded 82 noteworthy solar flares. The flares came primarily from two active regions of the Sun called AR 3663 and AR 3664. This video highlights all flares classified as M5 or higher, with nine classified as X-class solar flares. Six CMEs hurled toward Earth from the giant AR 3664 region hit our planet on May 10 at 16:45 UT, shaking magnetometers around the world and unleashing a powerful geomagnetic storm. [NASA’s God- dard Space Flight Center] T he aurora of May 10, 2024, pho- tographed in southwestern British Columbia, Canada. [NASA/ Mara Johnson-Groh]