Geomagnetic Storm (including energetic particles related to space weather, and solar flare radio blackout [R Scale])

Primary reference(s)

Cannon, P., M. Angling, L. Barclay, A. Thomson and C. Underwood, 2013. Extreme Space Weather: Impacts on engineered systems and infrastructure. Royal Academy of Engineering.

Additional scientific description

A geomagnetic storm refers to disturbances of the Earth’s magnetosphere, caused by sudden strong variations in the speed, density and magnetic properties of the solar wind. The resulting magnetic field variations within the magnetosphere generate electric currents in long conductors such as power lines and pipelines. The effects of geomagnetic storms range from mild (interference with aeromagnetic surveys) to extreme (electric power grids may experience blackouts or collapse) (NRC, 2019).

The largest recorded solar superstorm is known as the Carrington Event which occurred in 1859. It was associated with a large solar flare and the associated coronal mass ejections took only 17.6 hours to travel from the Sun to the Earth. It caused aurora in many parts of the world where they are not normally seen –even in Hawaii. One consequence of this solar superstorm was that telegraph systems across the world misbehaved with operators able to receive messages despite having disconnected their power supplies (Boteler, 2006; Clauer and Siscoe, 2006).

In March 1989, the third strongest recorded geomagnetic storm struck Earth. In less than a minute, induced current in transmission lines caused overload safety systems to trip closing down sections of the Quebec power network. A cascade effect then caused the network to collapse and the region to fall into darkness. Electricity was unavailable for nine hours, and restoration was made more difficult due to the fact that backup equipment had also been affected by the storm (CAA, 2016).

Examples of national geomagnetic storm scales:

Geomagnetic Storm Scales used by US: The National Oceanic and Atmospheric Administration (NOAA) Space Weather Scales were introduced as a way of communicating to the general public the current and future space weather conditions and their possible effects on people and systems. The scales have numbered levels, analogous to hurricanes, tornadoes, and earthquakes that convey severity. Possible effects at each level are also listed with how often such events happen and give a measure of the intensity of the physical causes (NOAA, 2019).

Geomagnetic Storm Scales used by Canada: At the Earth, magnetic storms are characterised by a K-level index that ranges from 0 to 9. Storms having little effect range from K=0–3, mid-level effects would be K=4–7, and strong storms with lots of impact would occur for K>7 (NRC, 2019).

Metrics and numeric limits

Not available.

Examples of drivers, outcomes and risk management

A geomagnetic storm is a major disturbance of Earth’s magnetosphere that occurs when there is a very efficient exchange of energy from the solar wind into the space environment surrounding the Earth. These storms result from variations in the solar wind that produces major changes in the currents, plasmas, and fields in Earth’s magnetosphere. The solar wind conditions that are effective for creating geomagnetic storms are sustained for (several to many hour) periods of high-speed solar wind, and most importantly, a southward directed solar wind magnetic field (opposite to the direction of Earth’s field) at the dayside of the magnetosphere. This condition is effective for transferring energy from the solar wind into Earth’s magnetosphere (NOAA, 2019).

While geomagnetic storms and disturbances can cause the aurora to be visible in the northern latitudes, there are more serious impacts to be considered. Impacts from geomagnetic storms and disturbances may cause impacts such as: damage to power grids through geomagnetically-induced currents (GIC); in extreme storms, impacts to power grid operations and stability are likely; and impacts on Global Navigation Satellite System (GNSS) accuracy and availability.

Advance notice is possible given that coronal mass ejection (CME) transit times from the Sun to Earth range from just under a day to several days (CMEs being the main driver of significant storms).