3.4 Hard X-rays

During the flare flash phase, usually a few minutes after the soft X-ray burst, another kind of apparently non-thermal radiation (as first noted by De Jager, 1965) is observed for many but not all flares: hard X-rays with energies of tens of keV up to a few MeV in extreme cases (see, e.g. Garcia, 2004). This radiation is due to electrons accelerated to very high energies right at flare onset which then hit the atoms of the lower denser layers and produce a bremsstrahlung continuum in the form of hard X-rays.

Since 2002, the RHESSI mission (Ramaty and Mandzhavidze, 2000Lin et al., 2003Jump To The Next Citation PointHurford et al., 2003), provides high-resolution imaging and spectroscopy from soft X-rays to Gamma-rays. New results are being published in a fast pace (see the External LinkADS for authors like Lin, Krucker, Hudson, Hurford and others).

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