Evolution of the sub-milliarcsecond nucleus of 3C 84 at 100 GHz

VLBI observations of 3C 84 at 3 mm indicate that the narrow jet detected in 1985 has evolved into a resolved component, 0.2 x 0.1 pc, separated from the nucleus by 0.2 pc. The position angle of the new component is close to that of the 1985 jet but differs from that of the 5 pc scale structure seen at lower frequencies. An unresolved nuclear source, less than 0.05 pc in size, has decayed monotonically from 14 Jy in 1982 to less than 0.5 Jy in 1987, corresponding to the decay in total flux density which followed a millimeter-wave outburst in 1980. The changes in source structure can be understood in terms of the diffusion of high-energy electrons with synchrotron lifetimes of about 2 yr from the radio nucleus into the halo. 10 references.