Decompose temporal variations of pulsar dispersion measures

Abstract

Pulsar dispersion measure (DM) accounts for the total electron content between a pulsar and us. High-precision observations for projects of pulsar timing arrays show temporal DM variations of millisecond pulsars. The aim of this paper is to decompose the DM variations of 30 millisecond pulsars by using Hilbert-Huang Transform (HHT) method, so that we can determine the general DM trends from interstellar clouds and the annual DM variation curves from solar wind, interplanetary medium and/or ionosphere. We find that the decomposed annual variation curves of 22 pulsars exhibit quasi-sinusoidal, one component and double components features of different origins. The amplitudes and phases of the curve peaks are related to ecliptic latitude and longitude of pulsars, respectively.