Space and near-Earth

A disturbance of Earth's magnetic field driven by the solar wind that disrupts power grids, satellites, navigation and radio.

Also: magnetic storm, aurora storm

A burst of X-rays from a solar flare that ionises the sunlit upper atmosphere and blacks out high-frequency radio there.

Also: radio blackout

A stream of energetic solar particles that raises the radiation dose of aircrew and astronauts and damages satellite electronics.

Also: solar energetic particles

Irregular electron density in the upper atmosphere that degrades radio links and satellite positioning.

Also: ionospheric storm, scintillation

Slowly varying currents driven through long conductors, such as grids and pipelines, by a changing magnetic field, overheating transformers and corroding pipes.

Also: GIC

Charging, single-event upsets or extra drag from the space environment that disable or shorten the life of satellites.

Swelling of the upper atmosphere during solar and geomagnetic activity that drags low satellites down, losing spacecraft and degrading orbit and collision predictions.

Also: satellite drag, atmospheric drag increase

A build-up of high-energy electrons trapped in the radiation belts that charges and damages satellite electronics for days after a storm.

Also: killer electrons, relativistic electron event

A widening region of weak geomagnetic field over the South Atlantic where trapped radiation dips low and repeatedly upsets satellites and orbiting crews.

Also: South Atlantic Anomaly

A comet or asteroid on a path that brings it close enough to Earth to carry a non-zero impact probability.

Also: asteroid, comet

A natural body striking the surface, producing a crater, a shock wave and ejecta.

Also: asteroid impact

A natural object breaking up in the atmosphere and releasing a blast wave that shatters glass and damages structures over a wide area.

Defunct satellites, rocket stages and fragments in orbit that can strike working spacecraft and crewed stations.

Also: orbital debris

Collisions that create fragments which cause further collisions, until an orbital band becomes unusable.

Also: Kessler cascade

A spacecraft or rocket stage falling back without control and scattering fragments over inhabited or sea areas.

Also: falling spacecraft

A launch, docking or on-orbit failure that endangers crew, spacecraft or people and property below.

Also: launch failure

Passage of Earth and its satellites through a dense stream of comet debris, raising the chance of hypervelocity hits that damage spacecraft.

Also: meteor storm, meteoroid impact on spacecraft