ZDI reconstruction in flattened polar view of the large-scale field of GJ 436. From the top, the radial, azimuthal, and meridional components of the magnetic field vector are displayed. The radial ticks are located at the rotational phases when the observations were collected, while the concentric circles represent different stellar latitudes: −30°, +30°, and +60° (dashed lines), as well as the equator (solid line). The geometry is predominantly poloidal, dipolar, and axisymmetric. The colour bar encapsulates the magnetic field strength, up to a maximum of 31 G.