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Abstract:
We studied the physical conditions of an erupting prominence observed
in the core of a coronal mass ejection, using combination of SOHO/LASCOC2
visible-light images and SOHO/UVCS ultraviolet data. Measured intensities and
profiles of the neutral-hydrogen Lyman-α and Lyman-β lines and the 977 ˚A C iii line
were used together with the visible-light brightness to derive the geometrical and
physical parameters of the prominence, such as the line-of-sight apparent thickness,
electron column density, kinetic temperature, and microturbolent velocity. These
parameters were used to constrain a non-LTE (i.e., out of local thermodynamic
equilibrium) radiative-transfer model of the prominence that provides the effective
thickness, electron density, and flow velocity, in a sample of points selected along
the prominence. The prominence can be described as a hot structure with low electron
density and very low gas pressure compared to typical quiescent prominences.
Intensities of the hydrogen lines were also used for a detailed determination of the
plasma line-of-sight filling factor, in the two prominence points where simultaneous
and cospatial LASCO-C2 and UVCS observations were available.
