A Geomagnetic Storm Watch has been upgraded by NOAA’s Space Weather Prediction Center (SWPC) to G3 on a scale of 1-5, where 5 is the most severe. Multiple coronal mass ejections (CME), including a full-halo CME are heading to Earth which will create a variety of problems around and just above the planet. The strong storms will also likely trigger the display or aurora, also known as “Northern Lights” in the Northern Hemisphere, in areas that usually don’t see them.
According to the SWPC, four CMEs are heading to Earth. The first was related to a November 27 filament eruption from the southwest which will pass mostly south and ahead of Earth. The second happened late on November 27 and is related to flaring on the Sun. The third, also late on November 27, was a partial-halo CME associated with flaring from an active region on the Sun and a subsequent filament eruption, merging with the second CME. And finally on November 28, a magnitude 9.8 flare associated with a full-halo CME is merging with the second and third CME is is due to blast Earth on December 1.
A class of CME that appears as an expanding halo of gas around the Sun in coronagraph images is considered a halo CME; the emitted gas is directed along the line of sight towards the observer. As these CMEs approach Earth, they appear larger than the Sun, making a halo of bright coronal emission completely around it.
The SPWC is calling for a “strong to extreme” storm to impact Earth, in which the Kp index may reach or exceed 7.
Coronal Mass Ejections (CMEs) are large expulsions of plasma and magnetic field from the Sun’s corona. They can eject billions of tons of coronal material and carry an embedded magnetic field, frozen in flux, that is stronger than the background solar wind interplanetary magnetic field (IMF) strength. CMEs travel outward from the Sun at various speeds, with some reaching the Earth as quickly as 15-18 hours and others requiring days to arrive. According to the SWPC, CMEs expand in size as they propagate away from the Sun and larger ones can reach a size comprising nearly a quarter of the space between Earth and the Sun by the time it reaches our planet. When the impacts arrive on Earth, a geomagnetic storm occurs.
One frequent side effect of these geomagnetic storms is the presence of aurora. The probability and location of aurora displays is based on the Kp index of the storm. The K-index, and by extension the Planetary K-index, are used to characterize the magnitude of geomagnetic storms. The SWPC says that Kp is an excellent indicator of disturbances in the Earth’s magnetic field and is used by SWPC to decide whether geomagnetic alerts and warnings need to be issued for users who are affected by these disturbances. Beyond signifying how bad a geomagnetic storm’s impact can be felt, the Kp index can also help indicate how low, latitude-wise the aurora will be.
The NOAA Space Weather Prediction Center (SWPC) is forecasting the geomagnetic storm on December 1 to have a Kp index of at least 7. The greater the number, the more vibrant aurora can be; in the Northern Hemisphere, a higher Kp index also means the aurora could establish itself high above the United States in southern locations that don’t ordinarily see the Northern Lights. Should the Kp index be less and around 4, aurora would only be visible in places like northern Michigan or Maine areas. A KP index of 7 or more could make the aurora present in clear skies in Boston, Chicago, and Seattle; a Kp index of 9 or more could illuminate the clear night skies of Washington, DC, Saint Louis, Denver, and even Salt Lake City. In past severe geomagnetic storms, the aurora has been visible as far south as Hawaii and the central Caribbean.
To view the aurora, you must be in an area free of obstructions, like clouds, and free of light pollution, such as street lights or city lights. They can be seen anytime in the dark by looking up or up towards the north sky. Depending on the intensity of the event and your location, they may appear as a floating ribbon of color, a brief flicker of greens, purples, or reds, or both. They may be visible briefly, intermittently, or over many hours.
While a higher Kp Index generally produces a more spectacular aurora display, it also presents more of a danger to systems that could be impacted by geomagnetic disturbances. Electrical system failures, grid failures, communication and navigation system faults, and more could happen if the geomagnetic storm is powerful enough.
For now, the SWPC says this strong geomagnetic storm will create a variety of problems with electrical, communications, and navigation systems. Voltage corrections may be required on some power systems while false alarms may be triggered by some protection devices. Intermittent satellite navigation and low-frequency radio navigation problems can also occur.
Above Earth, this geomagnetic storm can also damage satellites and spacecraft. These impacts can also effect astronauts on the International Space Station; in previous storms, astronauts were encouraged to go to more protected parts of the space station, according to NASA.