Slide 39 of 59
Notes:
Now we have the intensity at the surface of the neutron star, re-arranging (!) and inserting numerical values, we find that the temperature, if this were radiating like a blackbody, would be about 3e29K which is far, far too high to be a radio emission temperature. This corresponds to particle energies of kT~3e25 eV!!
Since particles of such high energies are not observed, there cannot be incoherent radiation of this type in the radio band.
Coherent emission can ‘raise’ the flux up to levels observed without the need for extremely high particle energies.