Radiation Processes Flashcards
What is the source of synchrotron radiation?
Highly relativistic e- gyrate about a B-field emit energy as radiation.
What happens to the beam shape of a relativistic e-?
emission is concentrated in direction of motion. In rest frame, beam is dipole. In lab frame, intensity is beamed.
Due to the beaming of synchrotron radiation, how is it observed?
Pulse, as emission is only visible once per orbit .
How can we describe the energy spectrum for synchrotron?
Power law.
n(E)dE = n_0 E_-p dE
What does the energy spectrum tell us about the luminosity per unit frequency?
L scales with v^-alpha. alpha can be written in terms of p.
What is another property of synchrotron emission?
high linear polarisation. depends on viewing angle.
Define Brightness temperature.
The temperature of a BB with the same intensity as the source.
Define the Effective temperature.
The temperature corresponding to the relativistic KE.
kT ~ gamma mc^2
When does synchrotron self absorption occur?
When brightness temperature is equal to effective temperature. e- cannot radiate more efficiently than BB.
What is Bremsstrahlung radiation?
emission due to charge acceleration from Coulomb interactions between particles in a plasma.
e- not ions loose energy.
Free-free emission.
Describe inverse compton scattering.
Relativistic e- lose energy by upscattering low energy photons.
Compare synchrotron and IC radiation.
IC is much less polarised than synch.
