Title: The Origin of Solar Filament Plasma Inferred from in situ Observations of Elemental Abundances,
Abstract: Solar filaments/prominences are one of the most common features in the
corona, which may lead to energetic coronal mass ejections (CMEs) and flares
when they erupt. Filaments are about one hundred times cooler and denser than
the coronal material, and physical understanding of their material origin
remains controversial. Two types of scenarios have been proposed: one argues
that the filament plasma is brought into the corona from photosphere or
chromosphere through a siphon or evaporation/injection process, while the other
suggests that the material condenses from the surrounding coronal plasma due to
thermal instability. The elemental abundance analysis is a reasonable clue to
constrain the models, as the siphon or evaporation/injection model would
predict that the filament material abundances are close to the photospheric or
chromospheric ones, while the condensation model should have coronal
abundances. In this letter, we analyze the elemental abundances of a magnetic
cloud that contains the ejected filament material. The corresponding filament
eruption occurred on 1998 April 29, accompanying an M6.8 class soft X-ray flare
located at the heliographic coordinates S18E20 (NOAA 08210) and a fast halo CME
with the linear velocity of 1374 km s$^{-1}$ near the Sun. We find that the
abundance ratios of elements with low and high First Ionization Potential such
as Fe/O, Mg/O, and Si/O are 0.150, 0.050, and 0.070, respectively, approaching
their corresponding photospheric values 0.065, 0.081, and 0.066, which does not
support the coronal origin of the filament plasma.