Relativistic particles: energization and radiation

Synchrotron radiation from relativistic electrons (and positrons), spiraling in magnetic fields, provides the only way that we can see many astrophysical objects. This is particularly true of extragalactic radio sources. The energetics of the radiation process, however, are not yet understood; simple application of current models runs into problems. The radio-loud plasma is ejected from an active galactic nucleus, and transported out to fill the radio source. If the electrons are energized in the galactic nucleus, they should radiate away their energy long before they have been able to propagate throughout the sources. Thus, we shouldn't see the sources as we do. How can this be understood? There are two possible solutions; I am currently working on both. One possibility is that the magnetic field is very inhomogeneous, being localized in filaments within the source. This slows down the radiative loss rate, compared to the well-mixed case. Another possibility is that the electrons are locally re-energized, for instance by plasma turbulence within the source that turns the bulk flow energy into radiation.

Some of this work is in collaboration with:

D.B. Melrose and M.A. Walker (RCfTA)

References:

Fluid flow and spectral aging in tailed radio galaxies

Synchrotron aging in filamented Magnetic fields

Where have all the old radio sources gone?

Research

Publications