Pulsar scintillation as a physical tool

Abstract

The interstellar gas contains irregularities of electron density having a wide range of physical scales. Pulsar radiation propagating through this inhomogeneous medium suffers a random modulation of phase which causes the received intensity to scintillate on a variety of timescales. Observations of the radio frequency spectrum and temporal variation of scintillation give information on the form of the irregularity spectrum and the distribution of density structure across the Galaxy. The high spatial coherence of pulsar radiation leads to the formation of extremely fine-scale diffraction patterns which also provide information on the motion of sources across the line of sight and the size of pulsar emission regions. Some uses of scintillation as a means of probing the interstellar gas and elucidating the physical properties of pulsars will be discussed.