1. Xu et al., ApJ 607, L131, 2004: or, how do flare footpoints work? First flare observations in the infrared 1.56  nominally is as deep as deep can be (the opacity minimum) Lucky to get an X10 flare (Oct. 29, 2003; good RHESSI observations)

2. Left: speckle WL preflare; right, flare image at 1.56 

5. 20:52:15 20:42:4620:39:45 Nice Sa”m Krucker RHESSI images

6. Footpoints and ribbons Anchor flaring coronal loops and interface with the mass reservoir there Traditional modeling in 1D radiation hydro approximation Hard X-ray (beam?) and UV-O-IR (deep atmosphere?) morphology significantly different

7. Nitty-gritty of the observations Dunn Solar Telescope @ near diffraction limit, high-order AO 1024 2 NIR array, 5nm passband @ 1.56 , 13 ms sampling, 91 arc s FOV IR has better seeing ( -6/5 ) but should have lower contrast

8. Ancient history! Ohki & Hudson, 1975

10. Blue: RHESSI 50-100 keV; Red: IR

15. Bruzek, 1964

16. Maltby models for sunspot umbra and particle ranges

17. Flare spectroscopy: Shoji & Kurokawa 1995

18. Annotated conclusions Backwarming response (theory somewhat confused) V x B @ 45 V/cm, but is this really a relevant E? Weak photospheric lines in the passband - do they contribute?