Probing cosmic plasma with giant pulses from the crab nebula pulsar

Abstract

A review and comparative analysis of results from studies of the effects of scattering on the interstellar medium using giant pulses of the Crab Nebula pulsar (B0531+21) are presented. This analysis was based on eight epochs of Very Long Baseline Interferometry (VLBI) radio observations carried out as part of the scientific program of the Radio Astron mission during 2011–2015. The scintillation timescale tscint and spectral index γ for the power-law energy distribution of the pulses were obtained for each observing epoch. The measured scintillation timescales are tscint = 7.5−123 s at 1668 MHz and tscint = 2.9 s at 327 MHz. The spectral indices are −1.6...−2.5. The frequency and time characteristics of the scattering were measured using two independent methods: based on the decorrelation bandwidth Δνd and the scattering timescale τSC. The angular size of the scattering disk θH of the pulsar was obtained, the phase structure functions constructed, and the distance to the effective scattering screen estimated. The derived diameter of the scattering disk θH at 1668 MHz ranges from 0.4 to 1.3 mas, while the scatteringdisk diameter at 327 MHz is 14.0 mas. The measured distance to the effective scattering screen ranges from 0.7 to 1.9 kpc, and varies from observation to observation in the same way as the scattering timescale and decorrelation bandwidth: τSC ≈ 0.9−5.8 μs and Δνd ≈ 40.7−161 kHz at 1668 MHz. The scattering timescale and decorrelation bandwidth at 327 MHz are 2340 μs and 68 Hz.