A high-speed stream of solar wind from a large coronal hole is expected to cause moderate geomagnetic storms over the next few days.

The sunspot, captured in observations by NASA’s Solar Dynamics Observatory (SDO), erupted on October 1, producing the second strongest solar flare of the current solar cycle. 

“Sunspots are areas where the magnetic field is about 2,500 times stronger than Earth’s, much higher than anywhere else on the Sun,” the National Weather Service explains. “Because of the strong magnetic field, the magnetic pressure increases while the surrounding atmospheric pressure decreases. This in turn lowers the temperature relative to its surroundings because the concentrated magnetic field inhibits the flow of hot, new gas from the Sun’s interior to the surface.”

Flares, meanwhile, are bursts of radiation emitted in the area near sunspots. This particular flare, from sunspot AR3842, could cause some disruption on Earth. It has already caused a shortwave radio blackout over Hawaii, according to spaceweather.com, and more could be on the way. According to the National Oceanic and Atmospheric Administration Space Weather Prediction Center (SWPC), the strong flare could result in an “immediate, wider area of strong degradation or signal loss in high frequency communication bands over much of the sunlit side of Earth”.

The flare may also be associated with a coronal mass ejection, where electrically charged plasma is sent out from the Sun.

“The flare was impulsive in nature but was associated with some USAF solar radio observatory reports that may indicate a possible coronal mass ejection (CME) could be associated with the flare,” the SWPC said on Wednesday. “Forecasters will analyze available coronagraph imagery when it becomes available to confirm if a CME did occur and if so, determine the potential for any Earth-directed component.”

The agency has since issued a minor-strong geomagnetic storm watch for October 3-5, with the coronal mass ejection expected to produce aurora on Earth, reaching northern US states and some of the lower Midwest. Some minor effects to technological infrastructure are expected, though they expect this to be mitigatable. The SWPC advises that the general public should consider monitoring their webpage for further updates as the geomagnetic storm develops.