  The neutron star spin down imposes a balance between the energy and angular momentum (E/L) losses of a pulsar. This translates into constraints on the region of emission. The E/L balance may be cogent in discriminating among the models of gamma-ray production. Hence, models which require the release of the entire luminosity at the polar caps should be excluded. Also models where the radiative zone is well inside the speed of light radius have some difficulties. It is argued that a local unbalance of E/L should generate a global instability of the magnetosphere, possibly quenching the emission at the polar caps. 
On Energy- Angular Momentum- Loss and Pulsar Spark Gaps