FIGURE 3. Proposed model for the inner jet of BL Lac.
From the following article:
The inner jet of an active galactic nucleus as revealed by a radio-to-
-ray outburst
Alan P. Marscher, Svetlana G. Jorstad, Francesca D. D'Arcangelo, Paul S. Smith, G. Grant Williams, Valeri M. Larionov, Haruki Oh, Alice R. Olmstead, Margo F. Aller, Hugh D. Aller, Ian M. McHardy, Anne Lähteenmäki, Merja Tornikoski, Esko Valtaoja, Vladimir A. Hagen-Thorn, Eugenia N. Kopatskaya, Walter K. Gear, Gino Tosti, Omar Kurtanidze, Maria Nikolashvili, Lorand Sigua, H. Richard Miller & Wesley T. Ryle
Nature 452, 966-969(24 April 2008)
doi:10.1038/nature06895
A shock propagates down the jet along a spiral streamline. The first flare occurs during the last 240° twist of the streamline before the flow straightens and becomes turbulent. The passage of the feature through the millimetre-wave core stimulates the second flare. A logarithmic scale of distance from the black hole, shown in terms of the Schwarzschild radius (RS), is used to illustrate phenomena on various scales.
