Coronal mass-ejections-kinematics of the 19 December 1973 event

Abstract

An eruptive prominence and coronal transient of 19 December, 1973 comprised one of the best-observed coronal mass ejection events during the skylab period (May, 1973–January, 1974). EUV observations show that the pre-eruptive quiescent prominence was (at 8000 K) not appreciably hotter than other quiescent prominences, but EUV radiation from it and its prominence-corona interface was unusually faint. The prominence material was distributed in helical threads which decreased in pitch angle during the early phases of eruption. No region of the prominence was markedly different from any other just prior to and during the eruption. For the first time, the temperature and density of rising prominence material were determined at great heights in the corona. At 3R _⊙, the prominence material was still confined in threads whose temperature and total hydrogen density were 2 × 10⁴ K and ∼1.5 × 10⁹ cm⁻³, respectively. Shortly after this observation (∼ 7hr after the start of the eruption), the prominence material expanded dramatically. A small portion (≲1%) of the prominence material was observed draining downward near the solar surface late in the event, and we infer that only a small fraction (∼10%) of the pre-eruptive prominence mass was expelled from the Sun. The remainder of the prominence apparently lay outside the instruments' fields of view. The bulk of the material expelled did not originate in the prominence. Both coronal and prominence material accelerated outward during the period of observations. A pre-existing streamer was disrupted by the outflowing material.