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This study investigates how dynamic processes in the Sun's chromosphere affect elemental abundance patterns in the solar corona, known as the First Ionization Potential (FIP) effect. Using hydrodynamic simulations combined with a new code called FIPpy, researchers found that when acoustic wave flux falls below a critical threshold, the fractionation process changes dramatically, producing unexpected patterns in elemental abundances. The results demonstrate that chromospheric turbulence suppresses FIP bias and that coronal composition reflects a delicate balance between ponderomotive acceleration from Alfvén waves and turbulent velocities.
Why it matters
These findings help explain observed variations in solar elemental abundances during different solar activity states, particularly during flares. Understanding these processes improves our ability to interpret solar observations and may have implications for predicting space weather effects that impact satellite operations and communications on Earth.
arXiv:2604.13174v2 Announce Type: replace-cross
Abstract: Elemental abundance variations in the solar corona, commonly characterised by First Ionisation Potential (FIP) bias, provide crucial diagnostics of chromospheric processes. The ponderomotive force model, which attributes fractionation to Alfv’en wave propagation, has successfully reproduced the observed fractionation patterns in various solar features. However, existing theoretical implementations rely on a static quiet Sun chromosphere, leaving the influence of chromospheric dynamics largely unexplored. We address this limitation by combining hydrodynamic simulations from HYDRAD with ponderomotive force calculations through FIPpy, a new open-source code. Comparing predictions between an initial VAL-C chromosphere and a heated chromosphere following impulsive nanoflare-like events, we show that the ponderomotive force model remains consistent under dynamic chromospheric conditions, while stronger changes in fractionation behaviour arise from variations in acoustic flux and turbulence. Most significantly, when acoustic wave flux drops below $sim5times10^6$ erg cm$^{-2}$ s$^{-1}$, mass-dependent thermal velocities dominate the fractionation process, producing counterintuitive patterns where Fe exceeds Ca in FIP bias, while high-FIP Ar shows fractionation. We demonstrate that any source of chromospheric turbulence will act to suppress fractionation. For flares, our results predict that the increased turbulence will suppress FIP bias, potentially explaining the observed abundance variations during flares. These findings suggest that coronal abundances and composition encode a sensitive balance between dominant mechanisms, determined by the ratio of ponderomotive acceleration to turbulent velocity.
Source: Chromospheric dynamics and turbulence regulate the solar FIP effect