Solar Storms and You!

Activity 4: Coronal Mass Ejection Plotting Activity


Coronal Mass Ejection's are major storms on the Sun which can hurl billions of tons of matter into space in a matter of a few hours. Traveling at millions of miles per hour, some of these clouds occasionally collide with the Earth and have produced power black outs and satellite damage. CMEs can start out with a size of only a few 100,000 kilometers, but fan out to millions of kilometers by the time they reach the Earth's orbit. Only CME's that emerge from near the Sun's eastern limb stand a chance of traveling all the way to Earth, so this is where astronomers look for early signs that one is on the way!


Students will construct a table of values and plot the points in order to make a prediction.


Student page and Teacher Answer Key
Colored pencils


  1. Plot CME 1 points from the appropriate tables and draw to scale the thickness of the CME indicated in the 'Width' column of the table.
  2. Plot CME 2 points from the appropriate tables and draw to scale the thickness of the CME indicated in the 'Width' column.
  3. By hand, sketch the path of the CME that hits the Earth and complete the shape of the CME using the width information from the table.
  4. Identify the location on the Sun where the sketched CME in procedure #3 will emerge so that it hits the Earth. This point is about halfway between the center of the Sun and the left (eastern) edge.
  5. Show that most CMEs do not hit the Earth by choosing other CME locations on the Sun and plotting the possible shape.
  6. The points in the table were calculated for an assumed CME speed of over 450 kilometers per second, however some CMEs can travel at a speed twice this fast. Challenge your students to re-calculate the table entries for a faster speed and redo steps 1-4 in this procedure. The students should see the shapes of the CME trajectories become flatter. The point where the CME that hits the Earth is ejected from the Sun will shift closer to the left (eastern) edge of the Sun.
Key Terminology

CME: A coronal mass ejection is a sudden ejection of mass from the outer layers of the Sun. They travel at speeds of up to 1000 kilometers per second and are millions of miles wide by the time they reach the orbit of the Earth. 


Coronal Mass Ejections don't all hit the earth, but the process requires just the right set-up. Typically, if you can see the CME being ejected near the limb of the sun, it will probably not affect the earth. The most likely eruptions that can affect us come from regions on the eastern half of the solar disk, provided they have the right speeds. CME speeds can vary from 400 kilometers/sec to over 1,500 kilometers/sec which means the arrival times and favorable launch points on the disk can vary quite a bit.

Related Web Resources

Visit the IMAGE/POETRY Page which has suggestions on how to study CMEs and their geomagnetic effects in more detail. This page gives information appropriate to a science fair project, or class project.
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This activity was developed by the NASA, IMAGE/POETRY 
Teacher and Student Consortium. 
For more information, and a list of other resources, visit 
the IMAGE/POETRYweb site.