A wide gap in the sun’s magnetic field is blowing a river of charged particles straight at Earth this week, and the result is already showing up in aurora forecasts: the northern lights are expected to be visible well south of their usual range over the next two to three nights, potentially reaching the northern United States and southern Canada.
The source is a coronal hole, a region where the sun’s magnetic field lines stretch open into space instead of looping back to the surface. Plasma escapes freely through these openings and accelerates into what forecasters call a high-speed stream. This particular stream has been clocked at roughly 520 km/s by instruments at the L1 Lagrange point, about 1.5 million kilometers sunward of Earth, and is gradually easing toward 440 km/s as the stream tapers off, according to the UK Met Office’s space-weather forecast. For comparison, the background solar wind typically drifts along at 300 to 400 km/s.
Those elevated speeds are compressing Earth’s magnetosphere and energizing particles that spiral down along magnetic field lines into the upper atmosphere, producing the glow we see as aurora. NOAA’s OVATION aurora model, which generates a continuously updated 30-minute forecast map, has been showing the auroral oval pushed noticeably southward since the stream’s arrival.
Where and when to look
NOAA’s Space Weather Prediction Center issues a three-day geomagnetic forecast broken into three-hour Kp index blocks, giving aurora chasers a night-by-night guide. The Kp index, derived from a global network of ground-based magnetometers, is the standard measure of geomagnetic disturbance. A Kp of 5 corresponds to a G1 (minor) geomagnetic storm on NOAA’s scale and can push visible aurora into northern-tier states like Montana, Minnesota, Wisconsin, Michigan, and Maine. A Kp of 6 or 7 would drag the oval farther south into the Upper Midwest and parts of the Northeast.
Current forecasts suggest Kp values will hover in the 4 to 5 range through late May 2026, with brief spikes possible if the solar wind’s embedded magnetic field swings southward at the right moment. That puts the best viewing window roughly between 10 p.m. and 2 a.m. local time, when the sky is darkest and the auroral oval is most likely to be overhead or on the northern horizon for mid-latitude observers.
A few practical tips: face north from a location with a clear, unobstructed horizon. Get as far from city lights as you can. Even when aurora is too faint for the naked eye, a smartphone camera set to night mode or a long exposure of 5 to 10 seconds can often pick up the green and purple glow. Cloud cover is the biggest wildcard, so check your local forecast before heading out.
Why coronal holes matter right now
Solar Cycle 25, the current 11-year activity cycle, is near or just past its peak, a phase when the sun’s magnetic field is at its most complex and coronal holes frequently appear at lower solar latitudes. Holes closer to the sun’s equator are more likely to send high-speed streams directly at Earth, which is why forecasters at NOAA’s SWPC track them daily on solar synoptic charts that map coronal-hole boundaries, magnetic polarity, and forecaster confidence levels.
Unlike a coronal mass ejection, which is a one-time eruption that can trigger intense but short-lived geomagnetic storms, a coronal-hole stream produces a more gradual, sustained disturbance. That is why forecasters are calling for multiple nights of elevated activity rather than a single dramatic spike. It also means the event is unlikely to cause significant disruptions to power grids or satellite operations, though operators are taking routine precautions.
NASA’s prediction tools, including the SIML-HSS model run by the Community Coordinated Modeling Center, use the measured size of a coronal hole and solar-wind speeds from the sun’s prior 27-day rotation to estimate when and how strongly a stream will reach Earth. The model’s reliance on measurements taken while the hole is still days from an Earth-facing position means rapid changes in the hole’s size can introduce forecast error, but the broad agreement between NASA and UK Met Office predictions for this event adds confidence to the outlook.
What could change
The biggest variable over the next few nights is the orientation of the interplanetary magnetic field, or IMF, carried by the solar wind. When the IMF points southward, it couples efficiently with Earth’s magnetic field and drives stronger geomagnetic storms. When it points northward, even fast solar wind can produce only modest aurora. Instruments at L1 detect the IMF’s orientation just 30 to 60 minutes before the wind reaches Earth, so forecasters cannot lock in storm intensity far in advance.
There is also the question of whether this coronal hole will deliver a repeat performance. The sun rotates once roughly every 27 days, so if the hole persists, a similar high-speed stream could sweep past Earth again in late June 2026. NOAA and the European Space Agency’s Solar Orbiter mission, which provides views of the sun’s far side, will be watching for signs of the hole’s evolution, but detailed measurements from the far side are not yet available in public forecast products for this event.
Small-scale density spikes or magnetic-field enhancements embedded within the broader stream could also briefly intensify conditions. No coronal mass ejection alerts are currently tied to this window, but forecasters are monitoring real-time data for any surprises riding on top of the high-speed flow.
How to track the aurora in real time
For anyone hoping to catch the lights, the most reliable tools are NOAA’s 30-minute aurora forecast map, which shows the auroral oval’s current position and estimated viewing probability by location, and the SWPC’s real-time Kp index page, which updates every three hours. Comparing those products against your local cloud forecast will give a much better sense of your chances than any single headline number.
The science behind these forecasts is well established, but the solar wind is inherently variable. Conditions can shift within minutes, which is exactly what makes aurora chasing part science, part luck, and entirely worth the effort on a clear night.
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*This article was researched with the help of AI, with human editors creating the final content.
