Relationship Between Scattering and Dispersion Measure of the Crab Nebula Pulsar

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 ne = 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 C2n = 0.00661 m−7, and the mean density variations in the Crab Nebula to be Δne ~ 0.02 cm−3, ne ~ 2 cm−3, so that Δne/ne ~ 0.01. In the comparatively active period 2009–2013, C2n = 0.0662 m−7, ne ~ 2 cm−3, Δne ~ 0.06 cm−3, and Δne/ne ~ 0.03.