Spooky Sky Created by a Coronal Mass Ejection

Caitlin Dempsey


Imagine looking up at the sky and seeing a eerie sight of greens streaming across the sky.  One might think this spooky looking display is the result of paranormal activity.  

The actual cause of this light show is less otherworldly, and is the result of an astronomical event known as a coronal mass ejection, or CME.  

What are coronal mass ejections?

Earth-targeted Coronal Mass Ejections, or CMEs, are solar events.

Coronal mass ejections (CMEs) are massive eruptions of charged particles, plasma, and magnetic fields that originate from the Sun’s outermost layer, known as the corona. These solar phenomena occur when magnetic energy stored in the corona is abruptly released, propelling vast amounts of matter into space.

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These particles can reach Earth after a few days and cause space weather called geomagnetic storms.

CMEs occur more frequently during periods of high solar activity, known as solar maximum, which is part of the Sun’s 11-year solar cycle.

What are geomagnetic storms?

Geomagnetic storms happen when the energy from the CME enters Earth’s magnetic field, called the magnetosphere. Magnetic storms can weaken communication signals and lead to electrical surges that can disrupt power grids.

How coronal mass ejections leads to auroras

CMEs can also cause auroras by causing reactions in the upper atmosphere, where oxygen and nitrogen molecules release particles of light called photons.

Over the course of several hours, the sun emits bursts of electrons, protons and other ions in the form of gasses.  These highly-charged particles speed through space at the rate of 2000 km/s.

Once they reach the Earth’s atmosphere, these particles come into forceful contact with oxygen and nitrogen.  The collision of these particles creates an explosion and energy is released in the form of light.  

The resulting light colors depends on the collision: nitrogen results in reddish-blue and collisions with atomic and molecular oxygen results in red or greenish-yellow light.

More: A spooky skyscape to celebrate Halloween – European Space Agency

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About the author
Caitlin Dempsey
Caitlin Dempsey is the editor of Geography Realm and holds a master's degree in Geography from UCLA as well as a Master of Library and Information Science (MLIS) from SJSU.