  Understanding how elemental abundances evolve during solar flares helps shed
light on the mass and energy transfer between different solar atmospheric
layers. However, prior studies have mostly concentrated on averaged abundances
or specific flare phases, leaving a gap in exploring the comprehensive
observations throughout the entire flare process. Consequently, investigations
into this area are relatively scarce. Exploiting the Solar X-ray Monitor data
obtained from the Chang'E-2 lunar orbiter, we present two comprehensive soft
X-ray spectroscopic observations of flares in active regions, AR 11149 and
11158, demonstrating elemental abundance evolutions under different conditions.
Our findings unveil the inverse first ionization potential (IFIP) effect during
flares for Fe for the first time, and reaffirm its existence for Si.
Additionally, we observed a rare depletion of elemental abundances, marking the
second IFIP effect in flare decay phases. Our study offers a CSHKP model-based
interpretation to elucidate the formation of both the FIP and IFIP effects in
flare dynamics, with the inertia effect being incorporated into the
ponderomotive force fractionation model.
