Solar Physics (2006) 236: 97–109 DOI: 10.1007/s11207-006-0126-1 C  Springer 2006 PERIODIC MOTION ALONG SOLAR FILAMENTS JU JING, JEONGWOO LEE, THOMAS J. SPIROCK and HAIMIN WANG Center for Solar-Terrestrial Research, New Jersey Institute of Technology, Newark, NJ 07102, U.S.A.; Big Bear Solar Observatory, 40386 North Shore Lane, Big Bear City, CA 92314, U.S.A. (e-mail: jj4@njit.edu) (Received 5 January 2006; accepted 23 March 2006) Abstract. We present observations of four filaments that exhibit large-amplitude periodic mass motion. Observations are obtained using the high resolution (2 ′′ ) and high cadence (1 min) Hα tele- scope system at the Big Bear Solar Observatory (BBSO). The motions found in these events are along the axis of the filaments, and are associated with the activity of a nearby flare or filament. The most characteristic properties of these motions are long period (≥80 min), large distance (≥ 4 ×10 4 km) of mass transport at much higher velocity (≥ 30 km s −1 ) than ever detected from filament motions. The velocity, period, dimension and damping timescale measured for these motions are presented, and discussed to identify the most plausible restoring force and damping mechanism. 1. Introduction Oscillatory mass motions in and around filaments (prominences) are often visible in Hα and Extreme ultraviolet (EUV) observations. They have attracted a great deal of attention from solar physicists, since the investigation of this motion may provide important clues to magnetohydrodynamic instability in filaments and also sheds light on the still not well understood filament formation process. The motion can be grossly arranged into two categories, according to the velocity amplitude (Oliver, 2001): (1) small-amplitude, small-scale vibrations of the fibrils which appear to affect only parts of the filaments, and (2) large-amplitude, large-scale mass motion along the filaments, whose influence could involve entire filaments. Small-amplitude oscillations have been frequently observed during the last twenty years (Oliver, 2001; Engvold, 2001; Oliver and Ballester, 2002). These observations use spectrographs to measure the temporal variation of Doppler sig- nals, and subsequent Fourier analysis, to yield information on the periodicity of the mass motions at the location of the filament along the slit. From the observations, many oscillatory parameters such as period, velocity amplitude, and damping time have been collected. The abundant observations of the small-amplitude oscillations allow the development of theoretical works that employ Alfv´ en modes, hybrid modes and additional, more complicated, fibril structures (Joarder, Nakariakov and Roberts, 1997; D´ ıaz et al., 2001). In contrast, large-amplitude oscillations have seldom been observed. The first report of a large amplitude oscillation was that of a so-called “winking filament”