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Solar radio bursts are strongly affected by radio-wave scattering on densityinhomogeneities, changing their observed time characteristics, sizes, andpositions. The same turbulence causes angular broadening and scintillation ofgalactic and extra-galactic compact radio sources observed through the solaratmosphere. Using large-scale simulations of radio-wave transport, thecharacteristics of anisotropic density turbulence from $0.1 \, R_\odot$ to $1$au are explored. For the first time, a profile of heliospheric densityfluctuations is deduced that accounts for the properties of extra-solar radiosources, solar radio bursts, and in-situ density fluctuation measurements inthe solar wind at $1$ au. The radial profile of the spectrum-weighted meanwavenumber of density fluctuations (a quantity proportional to the scatteringrate of radio-waves) is found to have a broad maximum at around $(4-7) \,R_\odot$, where the slow solar wind becomes supersonic. The level of densityfluctuations at the inner scale (which is consistent with the proton resonancescale) decreases with heliocentric distance as $\langle\delta{n_i}^2 \rangle(r) \simeq 2 \times 10^7 \, (r/R_\odot-1)^{-3.7}$ cm$^{-6}$. Due to scattering,the apparent positions of solar burst sources observed at frequencies between$0.1$ and $300$ MHz are computed to be essentially cospatial and to havecomparable sizes, for both fundamental and harmonic emission. Anisotropicscattering is found to account for the shortest solar radio burst decay timesobserved, and the required wavenumber anisotropy is $q_\parallel/q_\perp=0.25-0.4$, depending on whether fundamental or harmonic emission is involved.The deduced radio-wave scattering rate paves the way to quantify intrinsicsolar radio burst characteristics.

An Anisotropic Density Turbulence Model from the Sun to 1 au Derived From Radio Observations