Solar Storm From Giant Hole in Sun's Atmosphere Heading Straight for Earth

Earth is expected to be hit by a moderate-strength geomagnetic storm on September 4 as solar wind escapes from a huge hole in the sun's atmosphere.

On Thursday, the U.S. National Oceanic and Atmospheric Administration's (NOAA) Space Weather Prediction Center (SWPC) warned that a G2-level geomagnetic storm was "likely" to occur this Sunday.

A geomagnetic storm is a major disturbance to Earth's magnetosphere—the region surrounding the Earth that is dominated by our planet's magnetic field.

The magnetosphere can be disturbed whenever the sun shoots material our way, such as a stream of charged particles known as solar wind.

The sun
A NASA Solar Dynamics Observatory image of the sun on September 2, 2022, showing the dark coronal hole CH20+. Earth is expected to be hit by a moderate-strength geomagnetic storm on September 4. NASA/SDO/AIA

These interactions between solar material and the magnetosphere produce intense currents and heat up the upper regions of our atmosphere. This can have all sorts of effects, including increasing drag on satellites in low-Earth orbit, altering the path of radio signals and creating satellite navigation errors, and even creating harmful currents in electricity grids on the ground. These interactions can also cause colorful auroras in the sky.

Geomagnetic storms are measured in increasing strength from G1 to G5—minor to extreme.

The SWPC states that a G2 storm may involve changes to orbit predictions due to increased atmospheric drag, a fading of high-frequency radio propagation, possible voltage alarms in high-latitude power systems, and auroras possibly in states like New York and Idaho—though conditions will have to be right in order for people to see them.

A coronal hole high speed stream, or CH HSS, is behind the expected G2 storm. As the name suggests, a CH HHS is a stream of high speed solar wind that can interact with Earth's magnetosphere.

These streams are released from vast, open areas of unipolar magnetic fields on the sun, which allow the solar wind to escape easily into space. Because they are cooler and less dense than surrounding regions of the sun, coronal holes may appear as dark patches on the sun's surface depending on the imaging method.

As the streams of solar wind from coronal holes approach Earth, they catch up with and overtake the slower, ambient solar wind that already exists in the space between our planet and the sun. Intense magnetic fields can be produced at this interface between the fast and relatively slower solar wind streams.

Generally, geomagnetic storms aren't something that most people on Earth will notice, though people working in certain industries might want to keep track of them.

Geomagnetic storms are relatively common, occurring on about a monthly basis. Their frequency can increase or decrease depending on the sun's activity is increasing or decreasing as part of its roughly 11-year solar cycle.