Space weather and the Sun
02 October 2020
We all know the Sun is a big part of the weather we see and feel every day. What's less known is the role it plays in space weather. So, what is space weather, how does it affect us on Earth and how does the Sun factor in?
What is space weather and why does it matter?
Certain events that happen beyond the Earth's atmosphere are known as space weather. Space weather can affect our technology and the near-Earth space environment by:
- varying the Earth’s magnetic field
- enhancing electrical fields and currents in the atmosphere and the ground
- increasing the amount of radiation entering the upper atmosphere
- varying the density and stability of the upper atmosphere.
Space weather can disrupt some of the services we use as part of our everyday life, including GPS for navigation and radio communications. It can also damage satellites and the electricity transmission network.
How has space weather affected Earth?
On rare occasions extreme space weather has had a big impact. In 1859 the famous Carrington Event, described as a 'solar superstorm', saw massive electrical currents surge through telegraph lines. Luckily in those days our reliance on electronic systems was relatively low. It's said that the auroras produced were so bright people in the northeast United States could read newspapers by their light.
More recently, the Canadian province of Quebec suffered a nine-hour blackout in 1989, due to a solar storm. In 2003 a major geomagnetic storm led to the damage of 14 large electrical transformers in South Africa.
Other space weather events have seen polar flights re-routed, caused disruption and damage to satellites and even caused the explosion of sea mines during the Vietnam War.
The Sun's influence
The space weather environment is a large expanse of space. It starts at the edge of the atmosphere and is dominated by electrically charged particles, radiation, and the Earth's geomagnetic field. It extends another 150 million kilometres to the Sun and is filled with electromagnetic and particle radiation, solar wind plasma and interplanetary magnetic field.
The biggest influence on the space weather environment is the Sun.
Solar flares are sudden powerful eruptions of energy from the Sun that send electromagnetic and particle radiation into space. They can be followed by geomagnetic storms – temporary magnetic disturbances of the region influenced by Earth's magnetic field that cause electrical currents to flow through the Earth and its atmosphere.
Image: A solar flare flashes brightly, with a burst of solar material erupting into space below it. Credit: NASA
The solar wind is the outflow of solar material from the Sun's corona. It blows into space carrying the magnetic fields that originate in the Sun. Variations in the solar wind can cause changes in the Earth's magnetic field. Coronal mass ejections (CMEs) happen when a large amount of plasma and magnetic field bursts from the Sun's corona. These can couple with the Earth's magnetic field.
The solar cycle
The surface of the Sun is covered in electrically charged gases that generate powerful magnetic fields. The gases are always moving and this moves the magnetic fields too. All this motion and any change in the Sun's appearance or behaviour is called solar activity.
The Sun has a cycle of activity that takes place over approximately 11 years. A cycle begins with little activity and few sunspots – areas that appear dark because they're cooler than surrounding areas of the Sun's surface. This is called solar minimum. As the cycle progresses, the number of sunspots increases, as do events such as solar flares and CMEs. When sunspot numbers are at their peak, it's called solar maximum. After this, activity gradually declines, returning to solar minimum and the end of the cycle.
In September 2020 NASA announced that a new solar cycle had begun – Solar Cycle 25. This means we're at solar minimum now and we can expect activity on the Sun to increase over the years ahead.
The Solar Cycle 25 Prediction Panel of international experts estimates that peak sunspot activity will be in 2025 and that this may be a relatively quiet cycle. However, it could still produce noteworthy events.
The last solar cycle was considered to be quiet too, but on 23 July 2012 there was a CME of comparable strength to the Carrington Event. Fortunately it missed Earth. If it had been directed our way it could have caused widespread power blackouts.
Learn more about the solar cycle.
Video: The solar cycle as seen from space. Credit: NASA's Goddard Space Flight Centre
Solar minimum – what to expect
The announcement of the new solar cycle means we're at solar minimum. So what does that mean?
In solar minimum, solar activity doesn't stop – it just changes. For example, currently cosmic rays are at an all-time high in the space environment. These are high-energy particles that move through space at nearly the speed of light. Increased cosmic rays can have implications for space exploration space tourism, and the aviation industry – especially for flights in the polar regions, where there is an increased risk of radiation exposure.
Lower solar activity can help spacecraft operators. Space weather can affect a space object's orbit, causing it to speed up, lose altitude, and finally re-enter the atmosphere. If there's less activity it means fewer orbital corrections.
Predicting space weather
The effects of space weather can be serious. We watch and predict it to provide information to the industries and businesses that could be affected. This allows them to take precautions and prepare to reduce the risks.
Visit our Space weather services pages to see space weather forecasts and a host of other information about space weather.