Geophysical Research Letters

Coronal radio sounding: Non-Gaussian turbulence in the source regions of slow and fast solar wind



Structure functions of arbitrary order are analyzed using differential phase scintillation data obtained during the fourth solar conjunction of the Ulysses spacecraft in February–March 1995. The scaling features of these structure functions clearly discriminate between electron density fluctuations observed in coronal holes versus coronal streamers. The second order structure function, which is related to the power spectrum, shows essentially a scaling exponent ζ(p) = α −2, where p=2 and α is the spectral index of the three-dimensional wavenumber spectrum of electron density fluctuations. Higher-order structure functions provide evidence that these fluctuations are scale dependent and do not follow Gaussian statistics.