  Ellerman bombs (EBs) are short-lived and compact structures that are observed
well in the wings of the hydrogen H-alpha line. EBs are also observed in the
chromospheric CaII lines and in UV continua. H-alpha line profiles of EBs show
a deep absorption at the line center and enhanced emission in the line wings.
Similar shapes of the line profiles are observed for the CaII IR line at 8542
ang. It is generally accepted that EBs may be considered as compact microflares
located in lower solar atmosphere. However, it is still not clear where exactly
the emission of EBs is formed in the solar atmosphere. High-resolution
spectrophotometric observations of EBs were used for determining of their
physical parameters and construction of semi-empirical models. In our analysis
we used observations of EBs obtained in the H-alpha and CaII H lines. We also
used NLTE numerical codes for the construction of grids of 243 semi-empirical
models simulating EBs structures. In this way, the observed emission could be
compared with the calculated line spectra. For a specific model we found
reasonable agreement between the observed and theoretical emission and thus we
consider such model as a good approximation of the EBs atmospheres. This model
is characterized by an enhanced temperature in the lower chromosphere and can
be considered as a compact structure (hot spot). For the first time the set of
two lines H-alpha and CaII H was used to construct semi-empirical models of
EBs. Our analysis shows that EBs can be described by a "hot spot" model, with
the temperature and/or density increase through a few hundred km atmospheric
structure. We confirmed that EBs are located close to the temperature minimum
or in the lower chromosphere. Two spectral features, observed simultaneously,
significantly strengthen the constraints on a realistic model.
