Pulsars & Millisecond Pulsars: Physical Mechanisms

A pulsar contains a rapidly rotating neutron star with a magnetic axis generally tilted relative to its rotation axis. Charged particles accelerated in the magnetosphere produce radio, optical, X-ray, or gamma-ray emission in beams tied to the magnetic geometry.

Conservation of angular momentum makes a collapsed stellar core rotate rapidly, while magnetic flux compression greatly strengthens the field. Rotational energy powers magnetospheric particle acceleration and radiation. Over time isolated pulsars spin down; in close binaries, accretion can transfer angular momentum and recycle an old neutron star into a millisecond pulsar.

Pulse arrival times reveal periods stable enough for precision timing experiments. Measured spin-down rates imply energy loss, binary pulsars trace relativistic orbital effects, and millisecond pulsars cluster strongly in systems with histories of binary interaction.

Rotational energy powers much ordinary pulsar emission. Magnetic torques gradually spin the star down, while accretion in a close binary can transfer angular momentum and recycle it to millisecond periods.