A lower limit to the magnetic field in Cassiopeia-A
Open Access
- 1 August 1980
- journal article
- Published by Oxford University Press (OUP) in Monthly Notices of the Royal Astronomical Society
- Vol. 191 (4), 855-861
- https://doi.org/10.1093/mnras/191.4.855
Abstract
The magnetic field strength in the radio-emitting shell of the supernova remnant Cassiopeia-A should be greater than $$8 \times 10^{-5} G$$ if the bremsstrahlung by the electrons responsible for the non-thermal radio emission is not to exceed the upper limits to the gamma-ray emissivity set by the recent observations. This field strength is shown to be too large to be generated by a mere compression of the interstellar field by the supernova shock but must arise due to magnetohydrodynamic instabilities in the expanding shell. Gamma-ray generation through inverse-Compton scattering of photons in the surrounding H II region is also briefly discussed.