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Coronal Mass Ejections

Monitor coronal mass ejection (CME) events from the Sun. CMEs are large expulsions of plasma and magnetic field that can impact Earth 1-3 days after eruption.

About Coronal Mass Ejections

A Coronal Mass Ejection (CME) is a massive eruption of magnetized plasma from the Sun's corona into interplanetary space. Unlike solar flares, which are bursts of radiation, CMEs are physical clouds of solar material — billions of tons of plasma threaded with magnetic field lines — ejected at speeds ranging from 250 km/s (slow) to over 3,000 km/s (extremely fast). CMEs are often associated with solar flares and filament eruptions. When a CME is directed toward Earth (called a "halo CME" because it appears to surround the Sun in coronagraph images), it can trigger geomagnetic storms upon arrival 1 to 3 days later. Scientists analyze CME properties including speed, angular width (half-angle), type (S = slow, C = common, O = other), and whether it is likely to impact Earth. The SOHO and STEREO spacecraft provide coronagraph imagery used to detect and track CMEs.

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Frequently Asked Questions About Coronal Mass Ejections

How fast do CMEs travel?+
CME speeds range from about 250 km/s (slow) to over 3,000 km/s (extremely fast). The average CME speed is around 450 km/s. The fastest CMEs can reach Earth in under 15 hours, while slow ones may take 4-5 days. CME speed is one of the key factors determining the severity of the resulting geomagnetic storm.
What is a halo CME?+
A halo CME appears as an expanding ring (halo) of brightness surrounding the Sun in coronagraph images. This occurs when a CME is directed either toward or away from the observing spacecraft. Earth-directed halo CMEs are of particular concern because they indicate the plasma cloud is heading straight for our planet and is likely to trigger geomagnetic activity.
Can CMEs damage satellites?+
Yes, CMEs can significantly damage satellites. The energetic particles and enhanced radiation from CME-driven geomagnetic storms can degrade solar panels, cause single-event upsets in electronics, increase atmospheric drag on low-Earth orbit satellites (potentially causing orbital decay), and disrupt satellite communications and GPS accuracy.

Related Pages

Solar Dashboard

Overview of all solar activity

Solar Flares

X-ray burst data

Geomagnetic Storms

Resulting storm data

ISS Tracker

Station affected by CMEs

Glossary

Space weather terms