Photospheric Kelvin--Helmholtz Vortices as Possible Drivers of Coronal Heating: Implications of the DKIST Observations

Abstract

The Daniel K. Inouye Solar Telescope (DKIST) has resolved Kelvin--Helmholtz (KH) vortices at photospheric magnetic-flux boundaries with a characteristic wavelength of 65 km. I estimate whether these vortices can supply the photospheric driver for cross-scale plasma heating through reconnection across different heights from photosphere to low-corona. Using the simulated MURaM shear, density contrast, and 500 km vertical extent, together with a representative photospheric density, gives a shear-energy density of $1.35\times 10^2$ J m${}^{-3}$ and $2.2\times 10^{24}$ erg per characteristic vortex. Magnetic fields $1^{\circ }$--$7^{\circ }$ from the exact perpendicular orientation ($\mathbf{B}\perp \mathbf{k}$) remain KH unstable in an idealized calculation and provide an in-plane component that can be wound or compressed into current layers. The limiting case, in which the center-of-momentum shear reservoir becomes new magnetic free energy, gives $b_{\mathrm{cs}}=184$ G, identical to the ideal marginal-stability field and equivalent to a $7.6^{\circ }$ effective twist. This stores at most 135 J m${}^{-3}$ in the layers. Using empirical collisionless reconnection heating fractions of 0.28--0.44, the same twist mapped to weakly collisional heights gives ion heating from $\approx$20 eV at the photosphere to $\approx$1.4 keV in the low corona. For an illustrative, snapshot-based KH-active surface fraction of 0.03, quiet-Sun and coronal-hole losses require 5--8\% and 14--21\%, respectively, of the shear reservoir to become reconnecting magnetic free energy that reaches such heights. Active regions likely require a separate guide-field twist and helicity reservoir. The required upward transport has not been measured by DKIST, but it is directly testable.

1 figure, 2 tables, 7 pages without references