  We conducted a comprehensive study on the shell structure of the Cygnus Loop
using 41 observation data obtained by the Suzaku and the XMM-Newton satellites.
To investigate the detailed plasma structure of the Cygnus Loop, we divided our
fields of view into 1042 box regions. From the spectral analysis, the spectra
obtained from the limb of the Loop are well fitted by the single-component
non-equilibrium ionization plasma model. On the other hand, the spectra
obtained from the inner regions are well fitted by the two-component model. As
a result, we confirmed that the low-temperature and the high-temperature
components originated from the surrounding interstellar matter (ISM) and the
ejecta of the Loop, respectively.
  From the best-fit results, we showed a flux distribution of the ISM
component. The distribution clearly shows the limb-brightening structure, and
we found out some low-flux regions. Among them, the south blowout region has
the lowest flux. We also found other large low-flux regions at slightly west
and the northeast from the center. We estimated the former thin shell region to
be 1.3 degrees in diameter and concluded that there exists a blowout along the
line of sight in addition to the south blowout. We also calculated the emission
measure distribution of the ISM component and showed that the Cygnus Loop is
far from the result obtained by a simple Sedov evolution model. From the
results, we support that the Cygnus Loop originated from a cavity explosion.
The emission measure distribution also suggests that the cavity-wall density is
higher in the northeast than that in the southwest. These results suggest that
the thickness of the cavity wall surrounding the Cygnus Loop is not uniform.
