Physical conditions in steep-spectrum radio sources

Interplanetary scintillation observations of the radio sources 4C 31.04, 3C 67, 4C 34.07, 4C 34.09, OE 131, 3C 93.1, OF 247, 3C 147, 3C 173, OI 407, 4C 68.08, 3C186, 3C 190, 3C 191, 3C 213.1, 3C 216, 3C 237, 3C 241, 4C 14.41, 3C 258, and 3C 266 have been carried out at 102 MHz. Scintillations were detected for nearly all the sources. The integrated flux densities and flux densities of the scintillating components are estimated. Nine of the 21 sources have a low-frequency turnover in their spectra; three of the sources have high-frequency turnovers. The physical parameters are estimated for sources with turnovers in the spectra of their compact components. In most of the quasars, the relativistic-plasma energy exceeds the magnetic-field energy, while the opposite is true of most of the radio galaxies. Empirical relations between the size of the compact radio source and its magnetic field and relativistic-electron density are derived.