The influence of magnetospheric refraction on the apparent spatial structure of a pulsar emission region

The refraction of ordinary superluminous waves in a pulsar plasma is consid ered. The effect is found essentially to influence the apparent spatial str ucture of a pulsar emission region. This is of particular importance for th e interpretation of the observations of pulsar interstellar scintillations, which provide an opportunity of resolving the magnetospheres of nearby pul sars. When calculated with account for magnetospheric refraction, the depen dence of transverse ray separation on pulse longitude appears to be similar to that inferred by means of interstellar interferometry. It is shown that the differences in the character of the dependences observed at various fr equencies may be attributed to the frequency-dependent efficiency of refrac tion. Taking into account magnetospheric refraction makes it necessary to r econsider the estimate of the emission altitude derived from the apparent s ize of the emission region. The renewed estimate appears to be almost an or der of magnitude less, so that it is consistent with the emission altitudes obtained by other methods.