  Ballooning instabilities are widely believed to be a possible triggering
mechanism for the onset of substorm and current disruption initiation in the
near-Earth magnetotail. Yet the stability of the kinetic ballooning mode (KBM)
in a global and realistic magnetotail configuration has not been well examined.
In this paper, the growth rate of the KBM is calculated from analytical theory
for the two-dimensional Voigt equilibrium within the framework of kinetic
magnetohydrodynamic (MHD) model. The growth rate of the KBM is found to be
strongly dependent on the field line stiffening factor $S$, which depends on
the trapped electron dynamics, the finite ion gyroradius, and the magnetic
drift motion of charged particles. Furthermore, calculations show that the KBM
is unstable in a finite intermediate range of equatorial $\beta_{eq}$ values
and the growth rate dependence on $\beta_{eq}$ is enhanced for larger $\rho_i$.
The KBM stability is further analyzed in a broad range of $k_y$ for different
values of ion Larmor radius $\rho_i$ and gradient ratio $\eta_j \equiv
d\ln(T_j)/d\ln(n_j)$, where $T_j$ is the particle temperature and $n_j$ is the
particle density. The KBM is found to be unstable for sufficiently high values
of $k_y$, where the growth rate first increases to a maximum value and then
decreases due to kinetic effects. The $k_y$ at the maximum growth rate
decreases exponentially with $\rho_i$. The current sheet thinning is found to
enhance the KBM growth rate and the unstable $\beta_{eq}$ regime in the
near-Earth magnetotail.
