  Electron Compton scattering of target photons into the gamma-ray energy band
(inverse Compton scattering --IC--) is commonly expected to dominate the very
high energy spectra in gamma-ray bursts especially during the afterglow phase.
For sufficiently large center-of-mass energies in these collisions, the effect
of the electron recoil starts reducing the scattering cross section (the
Klein-Nishina regime). The IC spectra generated in the Klein-Nishina regime is
softer and has a smaller flux level compared to the synchrotron spectra
produced by the same electrons. The detection of afterglow emission from nearby
GRB 190819A in the very high energy (VHE) domain with H.E.S.S. has revealed an
unexpected feature: the slope of the VHE spectrum matches well the slope of the
X-ray spectra, despite expectations that for the IC production process, the
impact of the Klein-Nishina effect should be strong. The multi-wavelength
spectral energy distribution appears to be inconsistent with predictions of
one-zone synchrotron-self-Compton models. We study the possible impact of
two-zone configuration on the properties of IC emission when the magnetic field
strength differs considerably between the two zones. Synchrotron photons from
the strong magnetic field zone provide the dominant target for cooling of the
electrons in the weak magnetic field zone, which results in a formation of hard
electron distribution and consequently of a hard IC emission. We show that the
two-zone model can provide a good description of the X-ray XRT and VHE H.E.S.S.
data.
