  We describe the radiation phenomena which can take place in the physical
vacuum such as Cherenkov-type shock waves. Their macroscopical characteristics
- cone angle, flash duration, radiation yield and spectral distribution - are
computed. It turns out that the radiation yield is proportional to the square
of the proper energy scale of the vacuum which serves also as the vacuum
instability threshold and the natural ultraviolet cutoff. While the analysis is
mainly based on the theory engaging the logarithmic nonlinear quantum wave
equation, some of the obtained results must be valid for any
Lorentz-invariance-violating theory describing the vacuum by (effectively)
continuous medium in the long-wavelength approximation.
