Comparison of the Stokes V lightcurves of J0623 on obtained with ATCA on 14 Aug. 2022 (1.3 – 1.77 GHz) and 16 Dec. 2022 (1.3 – 1.6 GHz), and with MeerKAT on 27 Mar. 2023 (1.3 – 1.5 GHz). For clarity, we linearly resampled the data using 500 uniformly-spaced points in rotation phase, and smoothed the result with a Gaussian with a width of 5σ using SciPy’s gaussian_filterld function. The shaded regions show the 1σ variance in the Stokes V flux density. The structure appears to change over a timescale of around 6 months, which we speculate could be due to a magnetic cycle (see Section 4).