Space weather describes environmental conditions in space that can have an effect on Earth.
The most recognisable and visible space weather effect is arguably the auroras (Northern and Southern Lights). However, as well as these spectacular natural phenomena, space weather also represents a real threat and can have an impact on national infrastructure, technology, and communications systems.
What is Space Weather?
Space weather refers to the environmental conditions in Earth's magnetosphere, ionosphere and thermosphere due to the Sun and the solar wind that can influence the functioning and reliability of spaceborne and ground-based systems and services or endanger property or human health.
What Causes Space Weather?
The source of space weather is the Sun. The Sun is a million times larger than Earth and so distant that its light takes eight minutes to reach us. When violent solar phenomena occur, they create space weather effects on Earth, which can pose a hazard for human activities.
Space weather is the interaction between the Sun, the Earth's magnetic field and the atmosphere. Out location in the solar system is also a factor. The active elements of space weather are particles, electromagnetic energy and magnetic fields, rather than the more commonly known weather contributors of water, temperature and air. Magnetic fields, radiation, particles and matter which have been ejected from the Sun interact with the Earth's magnetic field and upper atmosphere to produce a variety of effects. These effects range from mild aurora borealis - the northern lights are often seen at high latitudes in the northern hemisphere, to the extreme, electric power grids may experience blackouts or collapse.
Types of Space Weather Event
Space weather is a threat to national infrastructure as it can have a devastating effect on technology.
|Storm Type||Travel Time||Physical Impact||Technological Impact|
|Geomagnetic||18-96h||Magnetic currents, increased ionisation in the ionosphere, heating in the thermosphere.||Power grid outages, GNSS, HF comms, satellite electronics, satellite positioning.|
|Charged particles||10 min to 1 day||Increased radiation levels for astronaughts and cabin crew, increased ionisation in the ionosphere||Damage to sensitive electronics, satelite heating, instrumet noise, avionics, digital chips, HF comms out in high latitudes.|
|Solar flares||8 min||Heating in the thermosphere||HF radio interferance, as above|
Coronal holes are regions of open magnetic field lines where high-speed streams of plasma can flow out from the Sun. If conditions are right, when these particles reach the Earth, geomagnetic storms can occur. High-speed streams interacting with the Earth are the cause of long-lasting (3 or 4 days) periods of geomagnetic activity, particularly in the auroral zone.
Coronal Mass Ejection/Solar Flares
A CME is the ejection of material from the Sun into interplanetary space. If the material is directed towards the Earth then the event may result in a disturbance to the Earth's magnetic field and ionosphere.
Solar flares are the sudden releases of energy across the entire electromagnetic spectrum. They are hard to predict, and the energy can be detected in Earth's atmosphere as soon as 8.5 minutes after the occurrence of a solar flare.
CMEs are often associated with flares. They can take days to reach Earth, carrying a local magnetic field from the Sun, and their arrival time is the focus of space weather forecasting
The ionosphere is a dynamic part of the upper atmosphere which acts as a reflector for long-range, high-frequency communications (HF comms). During a solar flare, the increase in x-ray radiation from the Sun causes the ionosphere to absorb rather than reflect signals and this disrupts communications systems on the sun-lit side of the Earth. The Sun may also emit radio bursts at multiple wavelengths causing various problems for communication and navigation systems.
Coronal holes on the Sun's equator and coronal mass ejections give rise to high-speed solar wind streams that buffet the Earth, disturbing the Earth's magnetic field and produce auroras. The charged particles from the solar wind ionise molecules in the atmosphere which we see as the northern lights.
Damage Caused by Solar Weather on Earth
Until the eighteenth century, geomagnetic storms have little or no effect on technology. As we rely more and more on electronics and electrical devices we are more susceptible to solar weather. The first telegraph outages reported on 17th November 1848 when the clicker of the telegraph connecting Florence and Pisa behaved in an unexpected manner during a brilliant aurora.
On 13th March 1989, a severe geomagnetic storm caused a transformer failure on one of the main power transmission lines in the Hydro Quebec system which led, in less than 90 seconds, to the collapse of the entire power grid. Six million people lost electrical power for 9 or more hours at an eventual cost of over $2 billion.
The same magnetic storm burned up a $36 million transformer in Salem Nuclear plant in New Jersey. These transformers have typical manufacturer lead times at least 12 months. Fortunately, a spare transformer from a cancelled nuclear plant in Washington State was available, and the Salem plant was able to reopen 40 days later.
Space weather can have a huge impact on humans living on Earth, and as our technological dependence increases the risks are getting larger and larger.