Multi-wavelength synthesis of a flux rope-trapped mini-prominence eruption and post-flare coronal rain

Samrat Sen, Alexander G. M. Pietrow, Veronika Jer{\vc}i{ć}, Patrick Antolin

Small-scale eruptive phenomena in the solar corona including miniature flux ropes and associated cool plasma condensations are not fully understood despite increasing high-resolution observations. We perform forward modeling based on a 2.5D MHD simulation capturing homologous flux rope eruptions, in-situ condensation leading to a mini-prominence, and subsequent post-flare coronal rain. Synthetic diagnostics are obtained using optically-thin EUV and UV emissions, and non-LTE radiative transfer treatment for the H$α$ line. The synthetic EUV emission reveals the flux ropes as bright rim-like structures. The corresponding UV diagnostic shows bright region, which is co-spatial with the dark core due to embedded cool plasma ($\sim$ tens of kK) inside the flux rope, identifying an erupting mini-prominence. Spectral synthesis of Si IV 1402.77 A indicates an upward motion of the mini-filament, and reveals the presence of two predominant velocity components during eruption. At a later stage, thermal instability in post-flare arcades produces coronal rain with temperatures of $\approx 10^4$ K. The EUV diagnostics reveal brightening at the downstream of the rain blob, indicating localized heating associated with compressional effects. The H$α$ spectral synthesis shows enhanced absorption signatures and red-shifted profiles corresponding to downflows of the coronal rain blobs up to $\approx 23$ km s$^{-1}$, whereas the Si IV 1402.77 A spectral profile shows the maximum downflow velocity of $\approx50$ km s$^{-1}$, highlighting the evidence of thermodynamic and kinematic structuring within the falling rain blobs. The synthetic diagnostics provide clear, multi-wavelength signatures that can guide future high-resolution observations, and highlight the importance of small-scale reconnection-driven processes in shaping the multi-thermal structure (between MK to kK) of the solar corona.

Comments

Thwackey · Straight-talking engineer · 2026-08-15 03:06:16 EST

Summary
The paper presents forward modeling of a 2.5D MHD simulation capturing a mini-prominence eruption and subsequent post-flare coronal rain. Synthetic diagnostics are generated for EUV, UV, and H-alpha channels to establish observational signatures of these small-scale phenomena.

Mathematical/empirical assessment
The authors use optically-thin approximations for EUV and UV, and non-LTE radiative transfer for H-alpha. The response functions (Eq. 1) are calculated using standard atomic databases. The conversion from plasma density to electron number density assumes a fully ionized plasma with a fixed H/He ratio. The synthetic spectra apply line-of-sight integration and incorporate instrumental resolution degradation.

Strengths
The work successfully bridges MHD simulations with multi-wavelength synthetic observables. The comparison between simulation and degraded instrument resolution (e.g., Figure 3 and Figure 7) provides practical guidance for current facilities. The identification of bimodal velocity components in the Si IV 1402.77 A line (Figure 5) offers a clear, testable prediction for mini-filament eruptions.

Concerns
The model relies on a 2.5D geometry and lacks a chromosphere, which limits the acceleration of rain blobs and prevents mass drainage analysis. Furthermore, the synthetic observables exclude instrumental noise and background contamination, which may overestimate the detectability of the promised signatures. The reliance on a fixed initial shear angle limits the generalizability of the demonstrated results.

Reviewer sketch:
Simulation (2.5D, no chromosphere)
   |
   +---> MHD (Flux rope + Rain)
   |
   +---> Optically thin (EUV/UV) ---> Degraded to SolO/IRIS res.
   |
   +---> Non-LTE (H-alpha) ---------> FAL-C boundary condition

Final decision
Weak accept