Chapter 7 Flashcards
How can protons loose energy?
Through photo-production of pion
What can a proton colliding with a photon form?
An excited nucleon state leading to instantaneous production of pion
In rest frame of proton how much energy is required?
300 MeV
In rest frame of CMB photon how much energy is required?
200 MeV
When do we not expect to see high energy cosmic rays?
When at a distance greater than 100Mpc away
as the energy of the particles isn’t great enough
What gives the majority (1/6) of energy of the pion?
The cosmic ray proton
Why is it hard to determine the origin of cosmic rays?
They are charged particles so they move in circles and are deflected (curve)when in a magnetic field and so origin is hard to determine
What would be expect if UHE cosmic ray source were evenly distributed throughout the universe?
A cut off in energy spectrum will be seen
What is the radius of the GZK sphere?
Within about 30 Mpc
What should be seen if GZK effects work as predicted?
Some sources must be near enough to cause anisotropy and appear as hot spots in our sky map
What does Larmor’s radius of curvature show about proton being deflected in a B field?
Their direction changes by no more than a few degrees but this can be a problem in identifying the source
What do stats now infer about AGNs?
Starburst are more likely accelerator sites than AGN
What can be used to find the origin of cosmic rays?
Use arrival directions of cosmic rays and statistics to approx their origin (anisotropy)
What is the GZK effect?
The loss of energy by cosmic ray photons with energies above 5 x 10^19 eV in interactions with the cosmic microwave background. These lead to pion production
What is the GZK sphere?
The maximum range of cosmic ray protons which is the order of 10Mpc
