The Spectrum Power of Interstellar Plasma Inhomogeneities in the Direction of Eleven Radio Pulsars

We have analyzed two-dimensional correlation functions from the dynamic spectra of 11 pulsars using the archival data of the "Radioastron" project. The time-sections of these functions were approximated by exponential functions with a power $α $. It is shown that this approximation describes the shape of the correlation function much better than the Gaussian. The temporal structure function $D(Δ t)$ for small values of the delay $Δ t$is a power law with an index $α $. The spectrum power of spatial inhomogeneities of the interstellar plasma is related to the power of the structure function as $n = α + 2$. We have determined the characteristic scintillation time and the power $n$ in the direction of 11 pulsars. In the direction of three pulsars (B0329+54, B0823+26, and B1929+10), the spectrum power of spatial inhomogeneities of the interstellar plasma turned out to be very close to the value for the Kolmogorov spectrum ($n = 3.67$). For other pulsars, it ranges from 3.18 to 3.86. It is shown that the measured scintillation parameters are significantly influenced by the duration of the observation session, expressed by its ratio to the characteristic scintillation time. If this parameter is less than 10, the parameter estimates may be biased: the values of $α $ and the characteristic scintillation time ${{t}_{{{scint}}}}$ may decrease.