  We present new high-resolution, multi-epoch, VLBA radio images of the
Galactic microquasar SS 433. We are able to observe plasma knots in the
milliarcsecond-scale jets more than 50 days after their launch. This
unprecedented baseline in time allows us to determine the bulk launch speed of
the radio-emitting plasma during a radio flare, using a new method which we
present here, and which is completely independent of optical spectroscopy. We
also apply this method to an earlier sequence of 39 short daily VLBA
observations, which cover a period in which SS 433 moved from quiescence into a
flare. In both datasets we find, for the first time at radio wavebands, clear
evidence that the launch speeds of the milliarcsecond-scale jets rise as high
as 0.32c during flaring episodes. By comparing these images of SS 433 with
photometric radio monitoring from the RATAN telescope, we explore further
properties of these radio flares.

High Energy Astrophysical Phenomena