Solar storms and space weather

Few solar storms reach earth and affect society. But our vulnerability to solar storms and other forms of space weather is increasing as we become more dependent on electricity and electronics.
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Foto: NASA/JPL.
Solstormar kan vara koronamassutkastningar eller soleruptioner.

Solar storms can be coronal mass ejections or solar flares.

The sun is constantly ejecting matter. A solar storm occurs when the activity on the sun becomes so intense that particles form electromagnetic fields that are hurled at high speed towards the Earth.

Two types of solar storms

Solar storms can be either coronal mass ejections or electromagnetic radiation bursts, solar flares. Coronal mass ejections give rise to geomagnetic storms, which are disturbances in the Earth's own magnetic field. This can damage electricity supplies. Solar flares can cause problems for radio communications and the GPS system.

Solar flares are large explosions on the sun's surface that occur near sunspots. Particles accelerate and emit radiation that can reach the Earth. Coronal mass ejections are large plasma clouds of free electrons and protons ejected from the sun's outer envelope (corona).

Solar flares can reach Earth quickly. Coronal mass ejections usually reach Earth within three to four days. However, the vast majority of coronal mass ejections deflect and pass alongside earth's protective magnetic envelope.

Possible consequences of solar storms

In extreme cases, solar storms can disrupt electricity supply and electronic communications and cause problems for rail and air traffic.

When electrical currents caused by the solar storm pass through high-voltage power lines, railway signalling systems, and oil and gas pipelines, they are called geomagnetically induced currents.

In the electricity network, induced currents can cause power lines and transformers to disconnect and even be damaged. This can cause short or long power cuts. Disruptions to electronic communications are mainly caused by longer power outages but can also occur when currents are induced in the copper lines of the telecoms network, damaging equipment.

Solar storms can also affect train services by inducing currents that cause signalling failures. Air traffic can be affected by disruptions to radio communications and GPS systems.

Forecasts and warnings

Space weather forecasts are based on satellites and ground stations. The US Advanced Composition Explorer (ACE) satellite measures, among other things, the speed and density of the solar wind and the direction of the magnetic field as it passes over the satellite. This information allows a geomagnetic storm to be predicted about half an hour before it occurs.

Measurement data from the satellite is collected by NOAA in the United States and can then be retrieved by space weather warning centres (RWCs). The data collected enables each centre to make its own forecasts. For Sweden, this work is carried out by the Institute of Space Physics in Lund.

In some cases, it is possible to monitor solar activity up to a month before a solar storm occurs, which makes it possible to give early warning of possible disturbances.

This information comes from the Swedish Civil Contingencies Agency (MSB) and Svenska kraftnät.