3.6. Magnetic Field Strength

The conventional estimate of magnetic field comes from the minimum-energy argument and corresponds to approximate equipartition between magnetic and relativistic particle energy. The strictures of the previous sub-section again apply. Two somewhat better methods might be useful in the future: measurement of the synchrotron self-absorption turnover frequency in hot-spots and jets and detection of Inverse Compton X-rays from the radio lobes (Feigelson et al. 1987; Miller et al. 1985). The latter group of authors estimates B > 0.05 - 0.1 nT for the bridges of a sample of low-luminosity FRII sources.