Ultra Low-Frequency Oscillations of a Solar Filament in H{\alpha}   Revealed With the Data of the Global Oscillation Network Group (Gong)
  The data of ground-based telescopes of Global Oscillation Network Group (GONG) obtained in the H-alpha line provide an opportunity to study the long-period oscillations of chromospheric filaments (quiescent prominence). For the first time, on the base of time-series of 5 days duration, combined from the observations of three observatories of the GONG, a new ultra-low mode, with period between 20 and 30 hours, was reliably detected in oscillations of a long-lived dark filament on the solar disc. 
V.I.Efremov, L.D.Parfinenko, A.A.Soloviev
astro-ph.SR