We report decaying quasi-periodic intensity oscillations in the X-ray ( 6–12 keV ) and extreme ultraviolet ( EUV ) channels ( 131 , 94 , 1600 , 304 Å ) observed by the Fermi GBM ( Gamma-ray Burst Monitor ) and SDO/AIA ( Solar Dynamic Observatory/Atmospheric Imaging Assembly ) , respectively , during a C-class flare .
The estimated period of oscillation and decay time in the X-ray channel ( 6–12 keV ) was about 202 s and 154 s , respectively .
A similar oscillation period was detected at the footpoint of the arcade loops in the AIA 1600 and 304 Å channels .
Simultaneously , AIA hot channels ( 94 and 131 Å ) reveal propagating EUV disturbances bouncing back and forth between the footpoints of the arcade loops .
The period of the oscillation and decay time were about 409 s and 1,121 s , respectively .
The characteristic phase speed of the wave is about 560 km s ^ { -1 } for about 115 Mm loop length , which is roughly consistent with the sound speed at the temperature about 10–16 MK ( 480–608 km s ^ { -1 } ) .
These EUV oscillations are consistent with the SOHO/SUMER ( Solar and Heliospheric Observatory/Solar Ultraviolet Measurement of Emitted Radiation ) Doppler-shift oscillations interpreted as the global standing slow magnetoacoustic wave excited by a flare .
The flare occurred at one of the footpoints of the arcade loops , where the magnetic topology was a 3D fan-spine with a null-point .
Repetitive reconnection at this footpoint could cause the periodic acceleration of non-thermal electrons that propagated to the opposite footpoint along the arcade and precipitating there , causing the observed 202-s periodicity .
Other possible interpretations , e.g .
the second harmonics of the slow mode are also discussed .