Coronal mass ejections observed during the Solar Maximum Mission: Latitude distribution and rate of occurrence

Abstract

Sixty‐five coronal mass ejections have been identified in a systematic examination of white‐light coronal images obtained between March and September 1980 by the coronagraph/polarimeter flown on the solar maximum mission spacecraft. These ejections were more uniformly distributed in position angle (or “projected” solar latitude) than the similar events observed during the Skylab mission in 1973–1974; 27% of the solar maximum mission mass ejections were centered at positions more than 45° from the solar equator. The average rate of occurrence of the observed mass ejections for the entire solar maximum mission epoch, based on the assumption that one coronagraph image per spacecraft orbit is sufficient for detection, was 0.9±0.15 per 24‐hour day. Application of the same sampling assumption to the Skylab data set leads to a rate of 0.75 per 24‐hour day and thus a change in this rate from the Skylab era (on the declining phase of sunspot cycle 20) to solar maximum mission (near the maximum of sunspot cycle 21) of only ∼20%.

Coronal mass ejections and their sheath regions in interplanetary space

“…They originate from gigantic magnetized plasma clouds, coronal mass ejections (CMEs 1 ), which are launched from the Sun at a quasi-regular basis. These eruptions were first revealed with space-based optical coronagraphs in the 1970s (Tousey 1973;Hildner 1977) and defined as distinct white-light features propagating through the coronagraph's field-of-view in time-scales from a few minutes to hours (e.g., Munro et al 1979;Hundhausen et al 1984). A schematic of an ICME showing also the leading fast forward shock (arc), and the sheath region.…”

III. Solar Maximum Mission Results

“…The CMEs may be related either to the flare explosions or eruptive prominences and, surprisingly, their frequency did not change by more than 20% as compared with the Skylab (1973-74) period , Hundhausen et al 1984. This seems to be related to a similar phenomenon in eruptive prominences, and its explanation is still controversial.…”

Solar Prominences – An Intriguing Phenomenon

“…Closely associated with the disparition-brusque phenomenon are the fascinating changes that occur in the coronal structure called coronal mass ejection (CME). From an observational point of view a coronal mass ejection may be defined as a change in the coronal structure that occurs on times scales up to several hours and involves the appearance of new bright features seen in the K-corona (Munro et al, 1979;Hundhausen et al, 1984). To the extent that the "new bright features" may be due to erupting prominence material, a study of coronal mass ejections forms part of prominence research, particularly as it applies to the disparition-brusque phenomenon.…”