Relationship Between Scattering and Dispersion Measure of the Crab Nebula Pulsar

Resumo

The correlation between scattering and the dispersion measure of the Crab Nebula pulsar B0531+21, obtained earlier from observations made on the Large Phased Array (LPA) at 111 MHz and at Jodrell Bank Observatory, has been confirmed using new independent measurements at the Pushchino Radio Astronomy Observatory and Jodrell Bank. The scattering varies in the range 10–115 ms, and can be explained by the passage of clouds of plasma in the nebula with sizes 10¹¹–10¹² m, electron densities n_e = 10³–10⁴ cm⁻³, and various degrees of turbulence in front of the pulsar. During a relatively quiescent period in 2002–2007, the turbulence coefficient in the direction of the Crab Nebula pulsar was found to be C²_n = 0.00661 m⁻⁷, and the mean density variations in the Crab Nebula to be Δn_e ~ 0.02 cm⁻³, n_e ~ 2 cm⁻³, so that Δn_e/n_e ~ 0.01. In the comparatively active period 2009–2013, C²_n = 0.0662 m⁻⁷, n_e ~ 2 cm⁻³, Δn_e ~ 0.06 cm⁻³, and Δn_e/n_e ~ 0.03.