Constraints on Interstellar Plasma Turbulence Spectrum from Pulsar Observations at the Ooty Radio Telescope

Refractive Interstellar Scintillation (RISS) effects on pulsar signals are powerful techniques for discriminating between different models that have been proposed for the power spectrum of plasma density fluctuations in the Interstellar Medium. The nature of the spectrum is considered to be a major input for understanding the underlying mechanism of interstellar plasma turbulence. Data from our long-term pulsar scintillation observations using the Ooty Radio Telescope (ORT) at 327 MHz are used to investigate the nature of the spectrum in the Local Interstellar Medium. The emerging picture is that the spectrum is Kolmogorov-like ($ \beta \approx 11/3 $) in the spatial scale range $\sim 10^6$ m to $\sim 10^{11}$ m, and there is evidence for excess power at larger spatial scales ($ \sim 10^12 - 10^13 $ m).