From the Quebec Blackout of 1989 to the historically intense Carrington Event 140 years earlier, geomagnetic storms are often memorable and spectacular events. This is why skygazers are excited about the recent news of an impending geomagnetic storm that will occur on Thursday evening and Friday evening, producing colorful auroras from northern California to Alabama. Though such storms are safe to view, they do carry some risk: possible widespread power outages.
The geomagnetic storm is expected to be a G4 class, according to the scale used by the U.S. National Oceanic and Atmospheric Administration (NOAA)'s Space Weather Prediction Center (SWPC). This is the second-highest level on the SWPC scale used to measure geomagnetic storms.
Known as a coronal mass ejection (CME), the solar outburst was created by a solar flare which erupted from our Sun on Tuesday evening. This means that tangled magnetic-field lines on the Sun suddenly snapped back into place. Like a whip hitting a ball of cream, the lash effect has ejected some of the Sun’s matter toward the Earth’s atmosphere. These types of events usually take place during the solar maximum, or a period of peak activity in the Sun’s 11-year cycle. While astronomers previously anticipated the Sun’s solar maximum would begin next year, the new CME causes some to believe it has already started.
Officially described as "severe," the G4 classification signifies that the geomagnetic storm could cause widespread voltage control programs in power grids, with some protection systems tripping out important assets during the event. The geomagnetic storm may also interfere with spacecraft operations — SpaceX CEO Elon Musk infamously flew 40 of his satellites into a geomagnetic storm in 2022 — particularly by causing tracking and surface charging problems. The geomagnetic storm could also disrupt satellite navigation and low-frequency radio navigation, as well as cause damage to “critical infrastructure technology.”
Yet the geomagnetic storm will also put on a beautiful show, with skies suffused in hues of green, red, pink and other colors. As a bonus, the geomagnetic storm is coinciding with the passing of the comet Tsuchinshan-ATLAS (official name: C/2023 A3). Since late September and through mid-October, Tsuchinshan-ATLAS has been visible along the eastern horizon in certain parts of the world. Tsuchinshan-ATLAS is usually invisible without a telescope, but for the next few days can be viewed with the naked eye. This will not be possible again for 80,000 years.
