A G1-class geomagnetic storm is possible overnight on Friday, July 10, through Saturday, July 11, potentially bringing displays of the northern lights also called the aurora borealis — to northern states along the U.S.-Canadian border. The potential arrival of a coronal mass ejection — a cloud of magnetic fields and charged particles from the sun — may make for a stronger display overnight on Saturday, July 11, through Sunday, July 12.
It comes a week after vivid displays of aurora were seen across northern U.S. states and southern Canada overnight on July 3-4, despite bright moonlight. With a new moon approaching on July 14, skies will be largely free of moonlight during the evening and around midnight, although a waning crescent moon will rise before dawn. Observing opportunities will be limited by the very short hours of darkness at this time of year. Here’s how to photograph the northern lights with a phone.
Northern Lights Tonight: Forecast
A stream of fast-moving solar wind from a coronal hole is expected to reach Earth on July 10-11. That should make Earth’s magnetic field more disturbed than usual, with mostly unsettled or active conditions and a chance of brief G1 geomagnetic storms. According to a forecast by space weather experts at the National Oceanic and Atmospheric Administration, “Geomagnetic conditions are anticipated to reach mostly unsettled and active levels 10-11 July under the onset of -CH HSS influences, with a chance for isolated periods of G1 (Minor) storming.” In practical terms, auroras may become a little more likely and could appear farther south than normal, but this is not expected to be a major storm. Another possible disturbance could follow overnight on July 11-12 if a CME reaches Earth as forecast. That could again bring aurora to northerly latitudes, although the timing and strength of any CME impact remain uncertain.
The UK Met Office’s space weather forecast suggests that a G2-class geomagnetic storm is possible on July 11-12. “Any CME arrival may increase activity once again … with Unsettled to G1/Minor storm conditions and a slight chance of a G2/Moderate storm interval (Kp6),” it states.
Northern Lights Forecast: What To Expect
Kp 5 conditions correspond to a G1 geomagnetic storm, and Kp 6 to a G2 geomagnetic storm. A G1 geomagnetic storm could mean aurora on the northern horizon from U.S. states close to the border with Canada — most likely across parts of Montana, North Dakota, Minnesota and Wisconsin. During a G2 geomagnetic storm, northern parts of Washington, Idaho, Montana, North Dakota, South Dakota, Minnesota, Wisconsin, Michigan and Maine stand a chance. There is also potential for observations of aurora from states farther south, including Oregon, Wyoming, Nebraska, Iowa, Illinois, Indiana, Ohio, Pennsylvania, New York, Vermont and New Hampshire. However, Kp does not guarantee that aurora will be visible from every location at a given latitude, and some locations may record only a faint photographic glow.
If the skies are clear, aurora hunters should look north during the darkest available hours, avoid light pollution, and use long-exposure settings on their phones or cameras. Cameras often detect faint aurora before the human eye can see color clearly.
Aurora Alert: Latest Updates
To check visibility in real time, use NOAA’s 30-minute aurora forecast or download apps such as Aurora Now, My Aurora Forecast or Glendale Aurora for near-real-time alerts and solar-wind data.
Whether an aurora display materializes largely depends on the interplanetary magnetic field, specifically its Bz component (you’ll find it in some of the above apps and on SpaceWeatherLive.com). Bz determines how easily solar energy enters Earth’s magnetosphere. When Bz is northward, coupling between the solar wind and Earth’s magnetosphere is generally less efficient. When Bz turns southward, magnetic reconnection can transfer more solar-wind energy into the magnetosphere, increasing the likelihood of geomagnetic and auroral activity. A sustained southward Bz — particularly when accompanied by elevated solar-wind speed and magnetic-field strength — can increase the likelihood of auroral activity. Values near or below −5 nT may be encouraging, but Bz alone cannot reliably predict whether aurora will be visible from a particular location.
What Causes The Northern Lights
The northern lights are caused by the solar wind, a constant stream of charged particles flowing from the sun that interacts with Earth’s magnetic field. While Earth’s magnetic field deflects much of the solar wind, disturbances can transfer energy into the magnetosphere and accelerate charged particles along magnetic-field lines into the polar upper atmosphere where they collide with oxygen and nitrogen atoms. These collisions excite the gases, causing them to release energy as shimmering light.
A CME is a large expulsion of plasma and magnetic field from the sun’s corona. CMEs are often associated with solar flares, although either phenomenon can occur without the other. Unlike solar flares, which travel at the speed of light, CMEs can travel at speeds of up to about 1,900 miles (3,000 kilometers) per second, with Earth-directed CMEs typically taking roughly one to several days to reach Earth. If they are Earth-directed, they can produce geomagnetic storms and auroras.
How To Increase Your Chances Of Seeing Aurora
Mid-latitude aurora sightings have occurred more frequently during the past two years because the sun reached the solar maximum phase of its 11-year solar cycle, when Earth-directed eruptions and other space-weather disturbances have been more common. The sun is now in its declining phase, with sightings of aurora from areas south of the Arctic Circle often limited to a faint glow low on the northern horizon.
For the best chance of seeing the northern lights, plan a trip between September and March to high northern latitudes near and above the Arctic Circle — in Alaska, northern Canada and the Nordic region, including northern Norway, Sweden and Finland, as well as Iceland. There, displays are typically more frequent, brighter and far more frequent and generally more dramatic than displays seen from the contiguous U.S., sometimes spreading across the entire night sky.
Wishing you clear skies and wide eyes.