Radio spectral ageing in a random magnetic field
Peter C. Tribble
Institute of Astronomy, Madingley Road, Cambridge CB3 0HA
Accepted 1992 August 24. Received 1992 August 14; in original form
1992 July 22.
Abstract
I study the aging of radio synchrotron emission from
relativistic electrons in a random magnetic field. There is a range of
break frequencies corresponding to the range in field strength, so that
the sharp break in the spectrum given by the Jaffe-Perola model is not
always seen, and the spectra can be very similar to that of the
Kardashev-Pacholczyk model. This explains the good fit of the
Kardashev-Pacholczyk model to observations, even though the
Jaffe-Perola model is more physically reasonable. The lack of an
exponential break in the spectrum does not mean that pitch angle
scattering does not occur. In the presence of inverse Compton losses,
the spectral shape is strongly dependent on rms field strength,
allowing equipartition estimates to be checked.
Key words: magnetic fields - radiation mechanisms: miscellaneous
- radio continuum: galaxies.
Contents:
- Introduction
- A simple model
- A free-streaming model
- Diffusion and inverse Compton Models
- Extra effects in real sources
- Conclusions
This article appeared in Monthly Notices of the Royal Astronomical
Society, vol 261, pp. 57-62 (1993). Copyright Royal Astronomical
Society.
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Peter Tribble, peter.tribble@gmail.com