Direct Injection of Chemically-Enhanced Plasma into a Solar Flare Arcade

The magnetic reconnection event that drives "standard" solar flares ejects material from the reconnection site, loading mass directly onto the newly-reconnected flare arcade. To et al (2024) suggested that this model can explain observations of the distribution of elemental abundances measured in post-flare loops: the reconnection exhaust directly injects plasma with coronal abundances onto the arcade, flowing from the apex downwards. We test this idea directly by modeling the spatiotemporal variation of elements with low first ionization potential (FIP), and directly inject material near loop apices. We show that this direct injection is capable of producing enhancements similar in magnitude and spatial spread across the corona to those observed during the gradual phase of an X11.9 flare. We also show that direct chromospheric heating strongly limits the width of the low-FIP enhancement to a narrow region near the injection site. The enhancement of low-FIP elemental abundances naturally explains bright knots commonly observed near the top of flare arcades.