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Relativistic beaming

The observed emission from a blazar is greatly enhanced by relativistic effects in the jet, a process called relativistic beaming. The bulk speed of the plasma that constitutes the jet can be in the range of 95% – 99% of the speed of light, although individual particles move at higher speeds in various directions.

The relationship between the luminosity emitted in the rest frame of the jet and the luminosity observed from Earth depends on the characteristics of the jet. These include whether the luminosity arises from a shock front or a series of brighter blobs in the jet, as well as details of the magnetic fields within the jet and their interaction with the moving particles.

A simple model of beaming illustrates the basic relativistic effects connecting the luminosity in the rest frame of the jet, S, and the luminosity observed on Earth, S: S is proportional to S × D, where D is the doppler factor.

When considered in much more detail, three relativistic effects are involved: