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The central radio source in M87 provides the best opportunity to study jetformation because it has a large angular size for the gravitational radius ofthe black hole and has a bright jet that is well resolved by VLBI observations.We present intensive monitoring observations from 2007 and 2008, plus roughlyannual observations that span 17 years, all made with the the Very LongBaseline Array at 43 GHz with a resolution of about 30 by 60 Rs. Ourhigh-dynamic-range images clearly show the wide-opening-angle structure and thecounter-jet. The jet and counter-jet are nearly symmetric in the inner 1.5milli-arcseconds (mas; 0.12 pc in projection) with both being edge brightened.Both show deviations from parabolic shape in the form of an initial rapidexpansion and subsequent contraction followed by further rapid expansion and,beyond the visible counter-jet, subsequent collimation. Proper motions andcounter-jet/jet intensity ratios both indicate acceleration from apparentspeeds of $\lesssim 0.5c$ to $\gtrsim 2c$ in the inner about 2 mas and suggesta helical flow. The jet displays a sideways shift with an approximately 8 to 10year quasi-periodicity. The shift propagates outwards non-ballistically andsignificantly more slowly than the flow speed revealed by the fastest movingcomponents. Polarization data show a systematic structure with magnetic fieldvectors that suggest a toroidal field close to the core.

The Structure and Dynamics of the Sub-parsec Scale Jet in M87 Based on 50 VLBA Observations Over 17 Years at 43 GHz