Looking into Pulsar Magnetospheres

Diffractive and refractive magnetospheric scintillations may allow a direct testing of the plasma inside the light cylinder. Unusual electrodynamics of the strongly magnetized electron-positron plasma allow separation of the magnetospheric and interstellar scattering. The most distinctive feature of the magnetospheric scintillations is their independence on frequency. Diffractive scattering due to small scale inhomogeneities produce a scattering angle that may be as large as 0.1 radians, and a typical decorrelation time of 10 seconds. Refractive scattering due to large scale inhomogeneities is also possible, with a typical angle of 10 radians and a correlation time of the order of 10 seconds. Some of the magnetospheric propagation effects may have already been observed. A number of observational results may possibly be attributed to scattering processes inside pulsar magnetospheres. The most convincing are the results of Sallmen et al. (1999) in which the frequency independent spread and the multiplicity of the Crab giant pulses with large variations in the pulse broadening times. Other observations that can be possibly attributed to magnetospheric propagating effects include an unusual scaling of broadening times for giant pulses (Hankins & Moffett 1998), ”ghosts” images of the Crab pulse and interpulse (Smith & Lyne 1999, Backer 1999), enhanced intensity fluctuations at very high frequencies (Kramer et al. 1997), enhanced scattering of nearby pulsars (Gupta et al. 1994, Rickett et al. 1999), comparatively large size of the Vela pulsar’s radio emission region (Gwinn et al. 1997), absence of mictrostructure with very short time scales (Popov 1999), frequency independent scintillations with bandwidth 4 MHz (Gwinn et al. 1999). Strong magnetic fields present in pulsar magnetospheres and the unusual electrodynamics of the one-dimensional electron-positron plasma both change the familiar effects of scattering and refraction in plasma. The un-