WD 2359-434. Top panel: chi-squared spectrum of W_λ measurements of nine contiguous ESPaDOnS spectra of WD 2359-434 taken during ten nights. Mid panel: phased variation of Hα line core equivalent width of WD 2359-434 using the same ephemeris as in Eq. (6). The smooth curve is the best fit sine wave. Bottom panel: variation of ⟨ B_z ⟩ of WD 2359-434 measured from ESPaDOnS spectra (black symbols) and from FORS spectra (red symbols), using the same ephemeris as above. The first two FORS1 measurements are not shown because they are too old to be accurately phased with the ephemeris. The smooth curve is the best fit sine wave to the ESPaDOnS data.