Coronal Mass Ejections

Contact person : For questions and more informations :
Dr. Angelos Vourlidas, SECCHI Mission Scientist

Coronal Mass Ejections (CMEs) are massive (1014 to 1016 grams) clouds of plasma that are ejected from the sun at speeds up to 2000-3000 km/s. Although the specifics are a hot topic of research, CMEs are caused by instabilities in the solar magnetic field, which is constantly evolving. Another research topic are the effects of CMEs in interplanetary space including their influence on the Earth’s space environment (`space weather’). We know that the most energetic CMEs cause geomagnetic storms and affect satellite operations and even electric power transmission lines at high latitudes.

To facilitate our research, we categorize CMEs in lists containing their time of occurrence, size, speed, position angle and maximum mass. The lists are compiled either by visual inspection of the images or automatically using various feature detection algorithms. Here, we use a visually compiled list of the LASCO observations which can be found here.

The CME lists should be used with caution, however, as they are subject to user bias or instrumental effects. We strongly encourage interested users to look at the images and movies themselves to verify on their own the information in the catalog.

Since January 2007, CME observations are available from a new set of coronagraphs and imagers aboard NASA’s STEREO mission. The instrument suite is called SECCHI and contains EUV solar disk images, white light coronagraphs and heliospheric imagers. It is installed on two almost identical spacecraft that are receding on either side of the Earth at a rate of 22.5 deg/year. The provide continuous and simultaneous coverage CME from two vantage points, away from the Sun-Earth line. Because the CME morphology is subject to projection effects, these events can appear quite different in each STEREO spacecraft or from SOHO. For this reason, we need to maintain separate CME lists for each spacecraft. CME lists from the SECCHI instruments are generated automatically based on the CACtus algorithm and are available here.

More information can be found on the SECCHI page.