THE SPATIAL STRUCTURE OF PULSAR EMISSION SOURCES DETERMINED USING INTERSTELLAR SCINTILLATION

Pulsars exhibit variations, or scintillation, of radio emission in tim e and frequency as a result of electron density inhomogeneities of the interstellar medium. Two sources with transverse separation greater t han the size of the diffraction pattern at Earth will produce independ ent scintillations. We use this idea to resolve pulsar magnetospheres. Here we present new observations at 102.7 MHz for four pulsars: PSR 0 834 + 06, 1133 + 16, 1237 + 25, and 1919 + 21. To study the decorrelat ion between pulsar signals at separated longitudes, we have calculated average cross-correlation functions in the time and frequency domains for data taken at the longitude of the leading edge of the pulse prof ile (as a reference) and at all other longitudes within the pulse. We present the dynamic spectra of pulsars at different longitudes of the mean profile, in which we see obvious decorrelation of the spectra at remote longitudes. From the falling cross-correlation coefficient with increasing longitudinal shift, we obtain the absolute value of the ba seline rho(0) between sources. We discuss our results in the framework of different pulsar models.