Particle Energies and Magnetic Energy in the Crab Nebula.

Some difficulties associated with the estimates of the probable values of the particle and magnetic energies in the model of the Crab proposed by Oort and Walraven are discussed. To overcome these, a model is described in which the high-energy electrons and positrons necessary to explain the synchrotron emission are secondary particles which are produced following nuclear collisions of a primary proton flux. It is found that the total energy in this proton flux must amount to 5 X 1050 ergs, while the continuously replenished flux of electrons and positrons, which have mean lives of only about 1-5 years, amounts to 1-5 X 1048 ergs. The magnetic field in the nebula is then 3 - 1 X 10-2 gauss. Though the total energy is much greater than that proposed in the Oort-Walraven model, the difficulties of acceleration and continuous replenishment of the electron-positron flux are thereby overcome. It is pointed out that the current radioactive energy input of the Crab is probably negligible in comparison with this total energy, which must have been derived from the initial explosion of the supernova.