A massive, butterfly-shaped hole has opened in the Sun's outer atmosphere, sending high-speed solar wind directly towards our planet and increasing the likelihood of geomagnetic storms and widespread auroras.
Identified as a coronal hole, it spans an estimated 310,000 miles (500,000 kilometres). These holes are regions where the Sun's magnetic field opens out into space, allowing solar wind to escape at high speed. In this case, the solar wind is heading straight for Earth.
The solar wind was expected to arrive around 14 September 2025. Forecasts suggest it may produce geomagnetic storm conditions ranging from G1 (minor) to G2 (moderate). If the embedded magnetic fields align well with Earth's own magnetic field, stronger activity is possible.
How Big Is It Compared to Earth?
The size of this coronal hole is vast: approximately 23 times wider than Earth. While the Earth has a diameter of around 7,917 miles (12,742 kilometres), this solar feature stretches across 310,000 miles (500,000 kilometres). This makes it one of the most visually striking features observed on the solar surface in recent months.
Despite its enormous scale, the effect it has on Earth depends on how the solar wind interacts with our planet's magnetosphere. If the magnetic fields connect effectively, more energy is transferred, leading to stronger geomagnetic activity.
What Effects Could Be Seen on Earth?
Geomagnetic storms occur when solar wind disturbs the Earth's magnetic field. These storms are classified on a G-scale from G1 (minor) to G5 (extreme). The upcoming storm is forecast to remain between G1 and G2 levels.
Under G2 conditions, auroras may be visible at mid- to high-latitudes. Regions like northern parts of the UK, Canada, Alaska, and Scandinavia could see colourful skies. In the Southern Hemisphere, auroras might appear over Antarctica, with a small chance of visibility in Tasmania and southern New Zealand.
Clear skies are said to improve the chances of spotting auroras. If the storm strengthens beyond G2, more southern areas in both hemispheres may also catch a glimpse of the auroral display.
Why is the Timing Important?
The event coincides with a period of increased geomagnetic activity around the equinox, known as the Russell-McPherron effect. First described in 1973, this effect explains why Earth is more susceptible to magnetic disturbances around the spring and autumn equinoxes.
On 22 September 2025, the Sun will shine directly over Earth's equator, and both hemispheres will receive nearly equal daylight. At the same time, Earth's magnetic poles align in a way that makes it easier for incoming solar wind to connect with the magnetosphere.
This alignment reduces the natural shielding effect created by Earth's tilt. As a result, even minor streams of solar wind, such as those coming from coronal holes, can cause more noticeable geomagnetic effects.
Should We Be Concerned?
At present, both the UK Met Office and the US NOAA's Space Weather Prediction Centre anticipate only moderate activity. The UK agency notes a possible G2-level storm, while NOAA leans towards a peak of G1. These forecasts could change depending on how the solar wind behaves upon arrival.
For most people, auroras will be the most noticeable outcome. However, moderate geomagnetic storms can occasionally disrupt satellite systems, navigation signals, and power grids at higher latitudes. At present, there is no indication of any significant risk.
Originally published on IBTimes UK
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