Pulsar observations and structure of the local ISM

Abstract

Results from new observations of pulsars using the Ooty Radio Telescope(ORT) are used for investigating the structure of the Local Interstellar Medium (LISM) and the nature of the plasma turbulence spectrum in theInterstellar Medium (ISM). The observations show anomalous scintillationtowards several nearby pulsars, and these are modelled in terms of large-scale spatial inhomogeneities in the distribution of plasma density fluctuations in the LISM. A 3-component model, where the Solar neighborhoodis surrounded by a shell of enhanced plasma turbulence, is proposed for the LISM. The inferred scattering structure is strikingly similar to the Local Bubble. The nature of the plasma turbulence spectrum is found to be Kolmogorov-like in the spatial scale range ˜ 10⁶ m to ˜ 10¹¹ m, and there is evidence for excess power at larger spatial scales.