2024MNRAS.527.1594T

Studies of the pulsar B0823+26 have been carried out using the Large Phased Array (LPA) radio telescope. At a time span of 5.5 yr, the amplitudes of the main pulse (MP), postcursor (PC), and interpulse (IP) were evaluated in daily sessions lasting 3.7 min. It is shown that the ratio of the average amplitudes of MP in the bright (B) and quiet (Q) modes is 60. For B-mode, the average ratio of MP amplitudes to IP amplitudes is 65, and the ratio of MP amplitudes to PC amplitudes is 28. The number of sessions with a nulling is 4 per cent of the total number of sessions. Structure function (SF) and correlation function analysis of MP, IP, and PC amplitude variations of over a long-time interval allowed us to detect typical time scales 37 ± 5 d and one year. The analysis of time variations shows that the time scale of 37 d is well explained by refraction on inhomogeneities of interstellar plasma, which is distributed mostly quasi-uniformly in the line of sight. This scintillation makes the main contribution to the observed variability. Analysis of the structure function showed that there may be a few days variability. This time scale does not have an unambiguous interpretation but is apparently associated with the refraction of radio waves on the interstellar medium. One-year variability time scale has not been previously detected. We associate its appearance with the presence of a scattering layer on a closely located screen at a distance of about 50-100 pc from the Earth.