VLB observations of the Crab Nebula and the wavelength dependence of interstellar scattering

We have measured the visibility of the Crab Nebula compact component (the pulsar NP 0532) with a 187,OOOA VLB interferometer operating at 26.3 MHz. The inferred Gaussian half-power diameter is I'!30(+ 0.23, - O'!13). Comparing this with other size determinations of this object, it is concluded that the size scales as A where n = 2 OS + 0 25 which implies for s, the turbulence power-law index, a range 3.5 < s < 4.3. This value is consistent with a Gaussian-like distribution of irregularities and some power-law distributions, including a Kolmogorov spectrum. Subject headings: interstellar matter - pulsars - radio sources