On May 1, 2013, NASA's Solar Dynamics Observatory (SDO) watched as an active region (left) of the sun erupted with a huge cloud of solar material—a heated, charged gas called plasma. This eruption, called a coronal mass ejection, or CME, sent the plasma streaming out through the solar system. Viewing the sun in the extreme ultraviolet wavelength of 304 Ångström, SDO provided a beautiful view of the initial arc as it left the solar surface. In addition to the images captured by SDO the CME was also observed by the European Space Agency/NASA Solar and Heliospheric Observatory (SOHO). SOHO houses two overlapping Large Angle Spectrometric Coronagraph (LASCO) telescopes where the bright sun is blocked by a disk so it does not overpower the fainter solar atmosphere. Both LASCO telescopes, named C2 and C3, observed the CME. The LASCO C2 coronagraph shows the region out to about 2.5 million miles, while the LASCO C3 coronagraph expands even farther out to around 13.5 million miles. Both of these instruments show the CME as it expands and becomes fainter on its trip away from the sun.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 184.108.40.206.0