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A report of the Aurora & Noctilucent Cloud Section (Director: Sandra Brantingham). A summary, by the Assistant Director of the Section, of noctilucent cloud (NLC) activity observed during the 2018 season.

Solar prominences were used to track the orientation and meridian bearing angles of their associated filaments over a nine-year period. Since filaments lie at right angles to the prevailing magnetic field, they were used as ‘compasses’ to plot its direction. The field lines marked by the filaments diverged from the meridian symmetrically, eastward and westward, with maximum divergence near the solar poles. The net mean field direction, over nine years, lay closely aligned with the N–S solar meridian. Filament formation was nevertheless asymmetrical, with an excess of filaments whose fields were directed westwards of the meridian. Asymmetrical filament formation appeared to be cyclical, as the proportion of westward-diverging to eastward-diverging filaments peaked during high sunspot activity, suggesting an interaction between the Sun’s poloidal and toroidal magnetic fields.