Enormous Solar Storm May Create Auroras Across Northern U.S. States

Auroras driven by a solar storm may be visible over some northern U.S. states Sunday if the skies are dark and clear.

On Thursday, the Space Weather Prediction Center (SWPC) issued a notice saying that a moderate-strength geomagnetic storm is "likely" to occur.

A stock image depicts two people looking at a bright aurora in the sky. Auroras may appear in the skies of northern U.S. states Sunday. basiczto/Getty

The storm, if it takes place, will be driven by a phenomenon known as a coronal hole high-speed stream (CH HSS). This is when a flow of charged particles from the sun is released from a region of its atmosphere cooler and less dense than the surrounding plasma, or highly ionized gas.

The open structures of these regions, called coronal holes, make it easy for the charged particles to be released into space as a high-speed stream.

When this stream arrives at Earth, it can disturb our planet's atmosphere and magnetic field, which has an effect on modern technology.

Increased atmospheric drag on satellites, radio communication failure and power-grid issues can all result from this solar activity. This disruption is known as a geomagnetic storm.

One notable effect of such storms is that they force auroras (the dancing colors in the night sky known as the Northern and Southern Lights) to shift away from the Earth's poles.

Depending on the strength of the storm, auroras can sometimes be seen in parts of the U.S. where they might not normally be visible.

For a storm with the same strength as the one expected Sunday, the SWPC states that auroras may appear as low as New York and Idaho. However, this will depend on the strength of the storm, as well as there being clear, dark skies.

The SWPC has published a list of major U.S. and world cities and their magnetic latitudes here, as well as the level of geomagnetic activity (known as the Kp-index) that would be required for an aurora to be seen there.

Sunday's storm is estimated to have a Kp-index of around 6 out of 9, though it could be lower.

For those able to see the northern lights, it may be possible to photograph them. Tips on aurora photography can be found around the internet.

Some tips include making sure you have a camera that allows the user to control f-stop, shutter speed, and ISO values manually. Since aurora photography will require long exposures, a tripod and extra batteries will also be needed.

Landscape photographer Dave Morrow has written a guide to photographing the Northern Lights. For instance, the camera's f-stop value, which refers to aperture width, should be wide at around f/2.8.

Morrow recommends that lenses should be focused to infinity and that exposure time or shutter speed should be set to between 1 to 15 seconds.

And, lastly, Morrow says that the ISO setting, which controls light sensitivity, should be between 500 and 2,000.

However, experimentation with photographic gear on the night may be crucial to find the ideal settings.