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2.1 The lighthouse model

Figure 2Watch/download Movie shows an animation depicting the rotating neutron star or “lighthouse” model. As the neutron star spins, charged particles are accelerated out along magnetic field lines in the magnetosphere (depicted by the light blue cones). The accelerating particles emit electromagnetic radiation, most readily detected at radio frequencies as a sequence of observed pulses produced as the magnetic axis (and hence the radiation beam) crosses the observer’s line of sight each rotation. The repetition period of the pulses is therefore simply the rotation period of the neutron star. The moving “tracker ball” on the pulse profile in the animation shows the relationship between observed intensity and rotational phase of the neutron star.
Watch/download Movie

Figure 2: GIF movie showing the rotating neutron star (or “lighthouse”) model for pulsar emission. Animation designed by Michael Kramer.
Neutron stars are essentially large celestial flywheels with moments of inertia ~ 1038 kg m2. The rotating neutron star model [242105] predicts a gradual slowdown and hence an increase in the pulse period as the outgoing radiation carries away rotational kinetic energy. This model became universally accepted when a period increase of 36.5 ns per day was measured for the pulsar in the Crab nebula [270], which implied that a rotating neutron star with a large magnetic field must be the dominant energy supply for the nebula [106].
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