Physical constrains of the beams

Two bright regions of radio emission can be observed in SS433. The first area is within cm of the core. Quasi-continuously ejected matter form wing-like structures which are stationary, despite Doppler evidence for motion at . This is evidence that new electrons are produced in a continuous way as the old electrons are swept away by the beams. At larger distances the amount of synchrotron emission is decreasing, probably due to adiabatic expansion.

The second region of bright radio emission is the brightening zone, at a distance of cm. After the observing campaign of 1985 it was suggested that the generation of relativistic electrons in this region could be due to the blob-like structure of the beams. Under these circumstances one can expect a bowshock for each blob. When the blobs all move at the same velocity, each blob will overtake the bowshock of the blob ejected earlier. This would happen at a distance independent of the difference in time between the ejection of the blobs. When a blob overtakes a bowshock enhanced radio emission can be expected due to compression of the magnetic field, density enhancements or generation of new relativistic electrons through turbulence. Since the observing campaign of 1987 this model has become less promising due to the evidence of a more continuous outflow (Vermeulen, 1989).

The two regions of bright emission are areas of enhanced radio emission. At any given moment the radio flux density is highly variable. Flares from the core can correlate with the generation of knots, almost always symmetric in the two beams. These knots move with a speed of , what is expected with shocks traveling to the medium.

Spectral index measurements during flaring modes indicates that a sustained generation of relativistic electrons is taking place over a period of several days. This happens in both enhanced regions. As the flares evolve the spectrum tends to soften. However a good analysis of the generation of synchrotron emission is difficult. Because the lifetime of relativistic electrons is larger than years, it is possible that these particles are produced in the core wings and radiate at greater distances, when for instance the magnetic field is compressed or aligned. At this moment is is not clear what the magnetic field configuration is in the beams.