  (Abridged) The motion of a Schwarzschild black hole with velocity $v_0 =
\beta_0 c$ through a constant magnetic field $B_0$ in vacuum induces a
component of the electric field along the magnetic field, generating a non-zero
second Poincare electromagnetic invariant $ ^* F \cdot F \neq 0$. This will
produce (e.g., via radiative effects and vacuum breakdown) an electric charge
density of the order of $\rho_{\rm ind}= B_0 \beta_0 /(2 \pi e R_G)$, where
$R_G = 2 G M/c^2$ is the Schwarzschild radius and $M$ is the mass of the black
hole; the charge density $\rho_{\rm ind}$ is similar to the Goldreich-Julian
density. The magnetospheres of moving black holes resemble in many respects the
magnetospheres of rotationally-powered pulsars, with pair formation fronts and
outer gaps, where the sign of the induced charge changes. As a result, the
black hole will generate bipolar electromagnetic jets each consisting of two
counter-aligned current flows (four current flows total), each carrying an
electric current of the order $I \approx e B_0 R_G \beta_0$. The
electromagnetic power of the jets is $L \approx (G M)^2 B_0^2 \beta_0^2/c^3$;
for a particular case of merging black holes the resulting Poynting power is $
L \approx {(G M)^3 B_0^2 /(c^5 R)}$, where $R$ is the radius of the orbit. In
addition, in limited regions near the horizon the first electromagnetic
invariant changes sign, so that the induced electric field becomes larger than
the magnetic field, $E>B$. The total energy loss from a system of merging BHs
is a sum of two components with similar powers, one due to the rotation of
space-time within the orbit, driven by the non-zero angular momentum in the
system, and the other due to the linear motion of the BHs through the magnetic
field.
