Kernel Heating and Ablation in the Impulsive Phase of Two Solar Flares

De Jager, C., Kernel Heating and Ablation in the Impulsive Phase of Two Solar Flares, Sol. Phys., 98, 267-280 (1985) (ADS)

The cartoon

(click on the image for a larger version)

A close-up view of how the chromosphere might "evaporate" or ablate under electron bombardment. Hydrostatic equilibrium has returned to this loop footpoint, which has a transition-region pressure some three to four decades above the quiet Sun's. As resolution has improved, the horizontal scale on the cartoon is looking less and less likely. In fact we really only have upper limits for the horizontal scale of the active field, and it may be far from hydrostatic equilibrium. This gives a fair idea of the geometry as envisioned then (a third of a century ago!) - compares with the hopeless complexity implied by the more modern Berger (black and white) or De Pontieu (color) cartoons that describe the same "layer" - the chromosphere, highly structured in three dimensions and not at all simplifiable as a layer..

      Note the placement of the top of the chromosphere at about 5000 km; this is much higher than the 1D semi-empirical models would put it, but does reflect the extension produced by 3D flows such as spicules. The Gurman cartoon considers this in a somewhat broader context, albeit one restricted to high-energy particles. When will MHD and particle acceleration meet on common grounds?

Date: 2007 March 11

Update: 2019 November 21