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Which solar events can cause severe space weather?

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Space weather Earth's full North Polar auroral oval, in an image taken in ultraviolet light by the U.S. Polar spacecraft over northern Canada, April 6, 1996. In the colour-coded image, which simultaneously shows dayside and nightside auroral activity, the most intense levels of activity are red, and the lowest levels are blue. Polar, launched in February 1996, was designed to further scientists' understanding of how plasma energy contained in the solar wind interacts with Earth's magnetosphere.

Severe space weather is primarily driven by dynamic solar events that release massive amounts of energy, mass, and momentum into the solar system. The most significant of these include:

Coronal Mass Ejections (CMEs): These are large eruptions of magnetized plasma from the Sun’s outer atmosphere, or corona. When these clouds of solar material are directed toward Earth, they can interact with the magnetosphere to trigger intense geomagnetic storms.12
Solar Flares: These are sudden, intense bursts of radiation and energy. While they can occur independently, they are often associated with CMEs. The hard X-ray pulses from flares can ionize Earth's upper atmosphere, leading to radio fade-outs and communication disruptions.12
Coronal Holes: These features generate high-speed streams in the solar wind. When these fast streams interact with slower solar wind, they form corotating interaction regions that can cause recurrent geomagnetic storms, particularly during the declining phase of the solar cycle.12

These events disturb Earth's magnetic environment, potentially impacting technological systems, power grids, and satellite operations.123