Solar Storm Heading for Earth: Huge Hole in Sun's Corona Means Auroras for North America

The National Oceanic and Atmospheric Administration’s (NOAA) Space Weather Prediction Center has issued a geomagnetic storm watch for September 11, meaning residents in the northern U.S. states may be able to see auroras tonight.

According to a map released by NOAA, people in Alaska and Canada will likely have the best views of the spectacular natural light shows, although those in the northernmost of the contiguous states—Minnesota and Maine, for example—will also have a good chance of seeing them. There is also a smaller possibility that the auroras will be viewable as far south as Iowa and Pennsylvania.

Space weather can have a variety of impacts on mankind and our technology. But the latest storm is ranked as "G2" or “moderate” on the NOAA’s space weather scale—which has five levels—meaning it likely won’t have any material affect on most people in the U.S.

In the northernmost parts of the country and Canada, however, power systems may experience voltage alarms and the propagation of radio waves may be affected. Furthermore, spacecraft operators on the ground may be required to take corrective actions as the storm could interfere with navigation systems.

The storm watch has been issued due to the onset of a "coronal hole high speed stream." Coronal holes are large regions in the Sun’s outermost layer, or corona, which are less dense and cooler than the surrounding material.

The magnetic fields in these regions allow charged particles, known as the solar wind, to escape more easily into space via high-speed streams. At the time of writing, the solar wind is travelling towards Earth at speeds of 561 kilometers per second or around 1,250,000 miles per hour.

When the solar wind collides with gases in the Earth’s magnetosphere— a region of the upper atmosphere filled with charged particles—dazzling colored light is produced creating auroras.

G2_watch_1 The NOAA have issued a G2 geomagnetic storm watch for September 11. NOAA

Coronal holes can develop at any time and location on the Sun, according to the NOAA, but they are more common and persistent during the years around a solar minimum—the period of least solar activity in the 11-year cycle of the Sun which we are currently heading into.

Because of their potential to generate geomagnetic storms on Earth, forecasters continually track coronal holes. A G5 level storm—the highest on the NOAA’s scale—could potentially cause power grid failures and widespread blackouts, while also significantly affecting satellites and the aviation industry.