ERUPTIVE PROMINENCE AND ASSOCIATED CME OBSERVED WITH SUMER, CDS AND LASCO (SOHO)

Observations of an eruptive prominence were obtained on 1 May 1996, wi th the SUMER and CDS instruments aboard SOHO during the preparatory ph ase of the Joint Observing Programme JOP12. A coronal mass ejection ob served with LASCO is associated temporally and spatially with this pro minence. The main objective of JOP12 is to study the dynamics of promi nences and the prominence-corona interface. By analysing the spectra o f O IV and Si IV lines observed with SUMER and the spectra of 15 lines with CDS, Doppler shifts, temperatures and electron densities (ratio of O IV 1401 to 1399 Angstrom) were derived in different structures of the prominence. The eruptive part of the prominence consists of a bub ble (plasmoid) of material already at transition region temperatures w ith red shifts up to 100 km s(-1) and an electron density of the order of 10(10) cm(-3). The whole prominence was very active. It developed both a large helical loop and several smaller loops consisting of twis ted threads or multiple ropes. These may be studied in the SUMER movie (movie 2), The profiles of the SUMER lines show a large dispersion of velocities (+/-50 km s(-1)) and the ratio of the O IV lines indicates a large dispersion in electron density (3 x 10(9) cm(-3) to 3 x 10(11 ) cm(-3)). The CME observed by LASCO left the corona some tens of minu tes before the prominence erupted. This is evidence that the prominenc e eruptions are probably the result of the removal of the restraining coronal magnetic fields which are in part responsible for the original stability of the prominence.