Measure the Motion|
of a Coronal Mass Ejection
Activity: Calculate the velocity and acceleration of a coronal mass ejection (CME) based on its position in a series of images from the Large-Angle Spectrometric Coronograph (LASCO) instrument on SOHO.
Materials: ruler, calculator, and a set of CME images from the LASCO instrument on SOHO. You can use the ones here or gather another set from http://sohowww.nascom.nasa.gov/gallery/LASCO/las001.gif.
Background: An important part of space weather research is to measure the velocity of CMEs and their acceleration as they leave the Sun. This is done by tracing features in the CME and measuring their positions at different times. In the sequence of images shown on the right, you can see a CME erupting from the Sun on the right side of the coronagraph disk. The white circle shows the size and location of the Sun. The black disk is the occulting disk that blocks the surface of the Sun and the inner corona. The lines along the bottom of the image mark off units of the Sunís diameter.
Procedure: Select a feature of the CME that you can see in all five images--for instance, the outermost extent of the cloud, or the inner edge. Measure its position in each image. Your measurements can be converted to kilometers using a simple ratio:
Further Questions and Activities
acting on the CME? How would these account for your data?
a set of lesson plans developed by Linda Knisely.
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