# The Origin of Solar Filament Plasma Inferred from in situ Observations of Elemental Abundances

## TL;DR

This study analyzes elemental abundances in a solar filament to determine its origin, finding that the plasma's composition aligns more with photospheric material than coronal, challenging existing models of filament formation.

## Contribution

The paper provides in situ elemental abundance measurements of a filament-associated magnetic cloud, offering evidence against the coronal condensation model for filament plasma origin.

## Key findings

- Filament plasma abundances are close to photospheric values.
- The elemental ratios do not support a coronal origin.
- Results challenge the condensation model of filament formation.

## 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.