The key element in the research of solar activi-
ties is the coronal magnetic field, which is however diffi-
cult to measure directly. Filament (or prominence) oscilla-
tions offer a new approach to derive important information
of the coronal magnetic field, which is called prominence
seismology. However, it is vital to determine the oscillation
mode before applying the prominence seismology since for
a given magnetic structure of a filament, the two different
modes of oscillation, namely, the longitudinal and trans-
verse, have different eigen frequencies. In low-resolution
observations, it is hard to distinguish the oscillation mode
since both modes of oscillations are associated with lateral
displacements, and the subtle difference between the two
modes becomes unresolvable. On 2013 March 15, there is a
filament oscillation event with a period of ∼63 minutes and
a decay timescale of ∼105 minutes, which was explained in
the literature to be a transverse oscillation or a mixture of
both transversal and longitudinal components with the same
period. With the analysis of the high-resolution SDO/AIA
data, we reexamine the filament oscillation event, and ar-
gue that this event is a longitudinal oscillation. We tenta-
tively propose a new method on how to identify the oscilla-
tion mode when the observational resolution is not so high.
A numerical simulation is also provided in order to match
B W. Xie
wb_xie@bao.ac.cn
1 School of Physics, Jilin Normal University, Siping 136000, China
2 School of Astronomy and Space Science, Nanjing University,
Nanjing 210023, China
3 Key Laboratory for Modern Astronomy and Astrophysics,
Nanjing University, Ministry of Education, Nanjing 210023,
China
4 School of Science, Linyi University, Linyi 276000, China
the observations, which leads to the ratio between the depth
and the width of the magnetic dip being 0.1.

EB00000003888K

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• A reexamination of a filament oscillation event on 2013 March 15