Astronomy and Astrophysics – Astronomy
Scientific paper
May 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...210.9332r&link_type=abstract
American Astronomical Society Meeting 210, #93.32; Bulletin of the American Astronomical Society, Vol. 39, p.216
Astronomy and Astrophysics
Astronomy
Scientific paper
The exact cause of coronal mass ejections (CMEs) remains unsettled despite three decades of observations since their discovery in the early 1970s. Their association with events at the Sun, such as prominence eruptions and solar flares, is often established from a near-time and -position angle coincidence on the solar disk and limb. Using a list from randomly chosen CMEs in the LASCO/C2 catalog, a comparison is made of the number of associated events from observations at solar maximum (1999-2000) and during the declining phase of the solar cycle (2004-05). Images of the Fe XII and He II lines from SOHO/EIT are used to locate events associated with the CMEs. The results show solar maximum CMEs having four times more associated prominence eruptions, without an associated flare, than at solar minimum (12% vs. 3%). CMEs at solar minimum have five times the number of flare-associated prominences (11% vs. 2%), and twice the number of flare-associated active regions (29% vs. 14%). A histogram of the CMEs speed distribution shows a trend with a skewed peak in the range of 200-399 km/s at both phases of the solar cycle. When separated into event-associated cases, a similar distribution with speed is found with the flare-associated events, whereas a peak in the percent of CME-associated prominence eruptions appears in the range of 600-799 km/s. Using this information and the fact that prominence eruptions were most commonly observed at the solar limb, we estimate that the mean prominence-associated CME speed lies within the range of 600-799 km/s and the mean flare-only associated speed lies in the 200-399 km/s range. Such results point to the importance of prominence eruptions in fast-propagating CMEs.
This work was funded by the NSF through a Research Experience for Undergraduates position at the University of Hawai'i's Institute for Astronomy.
Morgan Huw
Rasca Anthony
Rifai Habbal Shadia
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