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The evolution of magnetic fields in the tenuous solar corona is predominantly governed by the motions of the underlying dense photosphere. Despite, coronal magnetic restructuring driven by magnetic reconnection between interacting coronal fields can sometimes react backwards to change photospheric magnetic fields. However, the mechanism of reactions remains undetermined. Here, we report the discovery of a back-reaction phenomenon: the untwisting of coronal loops that become twisted during reconnection in an eruption results in enhanced currents at the boundary of their footpoint away from the eruption, manifesting as the growth of a sunspot scar. It is revealed to arise from the Alfvenic reverse transfer of magnetic twist from the corona to the lower atmosphere, thanks to joint space observations and a magnetohydrodynamics simulation. These findings provide a viable and quantitative interpretation for the majority of puzzling photospheric changes associated with coronal mass ejections and/or flares and warn for unexpected magnetic field evolutions in sunspots and starspots.

Using the $C-$metric in the context of $F(R)$ gravity coupled with the ModMax nonlinear electromagnetic field (the $F(R)-$ModMax theory), we derive an exact black hole solution in a four-dimensional spacetime. We then examine how various parameters influence the behavior of accelerating ModMax black holes. Treating this black hole as a thermodynamic system, we calculate the Hawking temperature and entropy for the accelerating ModMax black holes within the framework of $F(R)$ gravity. Subsequently, we explore the impact of the parameters in $F(R)-$ModMax theory on the Hawking temperature and entropy. We also assess local stability by analyzing the heat capacity. Additionally, we investigate both the angular shadow and the shadow radius of an accelerating black hole in the context of $F(R)-$ModMax gravity.

In this work, we revisit the generalized emergent dark energy model by confronting it with DESI DR2 baryon acoustic oscillation measurements, in combination with joint CMB data from ACT, SPT, and Planck, as well as Type Ia supernova samples including Pantheon$^+$, DES-Dovekie, and Union3. We find that the GEDE model remains compatible with the $Λ$CDM paradigm, with no statistically significant preference for deviations when all datasets are combined. In particular, the key model parameter $Δ$ is consistent with the $Λ$CDM value $Δ= 0$ within $2σ$ once SNe Ia data are included. Despite this overall agreement, the GEDE model does not exhibit the phantom crossing suggested by DESI DR2. Instead, the evolution of the dark energy equation of state $w(z)$ indicates that the model behaves either as a full phantom ($w < -1$) or quintessence ($w > -1$), depending on the dataset combination, without a clear transition across $w = -1$. When Pantheon$^+$ data are included, the model converges closely to $Λ$CDM with $w \simeq -1$. The GEDE model does not alleviate the existing cosmological tensions. The inferred values of $H_0$ remain in the range $67.9$-$69.8\ \mathrm{km,s^{-1},Mpc^{-1}}$, while the sound horizon $r_d$ and clustering parameter $S_8$ remain consistent with $Λ$CDM, failing to resolve the $H_0$ and $S_8$ tensions. Finally, both Gaussian significance levels ($<2σ$) and Bayesian evidence ($\ln B_{i,j} < 1$) indicate no statistically significant preference for GEDE over $Λ$CDM. We conclude that, although DESI DR2 hints at dynamical dark energy, the GEDE model remains observationally indistinguishable from $Λ$CDM and does not support the Quintom-B-type behavior suggested by DESI DR2.