The origin of the solar corona’s million Kelvin temperatures remains a central unsolved problem. While the nanoflare hypothesis is widely accepted and describes magnetic reconnection events at coronal current sheets that are slowly formed by complex driver flows at the solar surface, the possibility remains that macroscopic fluid instabilities self-organize microscale current sheets where none previously existed. We present the first laboratory demonstration that the Rayleigh-Taylor instability self-organizes antiparallel magnetic fields, driving reconnection at $r_{\max }\approx 0.078$ that heats electrons to $T_e\approx 70.8\pm 6.5\mathrm{eV}$, twice that of shock-dominated cases. Radiative magnetohydrodynamic simulations confirm Joule heating dominates viscous dissipation. Despite differing global energy storage, our dimensionless parameters ($R_m\approx 3\times {10}^3$, $\beta \in 0.1-1$) map to coronal rain nanojet conditions via Ryutov scaling, complementing the tearing-mode theory. This establishes the Rayleigh-Taylor instability as an efficient driver of nanoflare heating in coronal settings characterized by velocity shear and large density gradients, such as found with coronal rain.

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• High-energy-density plasmas
• Laboratory studies of space & astrophysical plasmas
• Laser-plasma interactions
• Magnetic reconnection