  We present observations of a B7.9-class flare that occurred on the 24th
January, 2015, using the Atmopsheric Imaging Assembly (AIA) of the Solar
Dynamics Observatory (SDO), the EUV Imaging Spectrometer (EIS) and the X-Ray
Telescope of Hinode. The flare triggers the eruption of a dense cool plasma
blob as seen in AIA 171\AA,\, which is unable to completely break out and
remains confined within a local bundle of active region loops. During this
process, transverse oscillations of the threads are observed. The cool plasma
is then observed to descend back to the chromosphere along each loop strand. At
the same time, a larger diffuse co-spatial loop observed in the hot wavebands
of SDO/AIA and Hinode/XRT is formed, exhibiting periodic intensity variations
along its length. The formation and evolution of magnetohydrodynamic (MHD)
waves depend upon the values of the local plasma parameters (e.g. density,
temperature and magnetic field), which can hence be inferred by coronal
seismology. In this study we aim to assess how the observed MHD modes are
affected by the variation of density and temperature. We combined analysis of
EUV/X-ray imaging and spectroscopy using SDO/AIA, Hinode/EIS and XRT. We show
that the evolution of the detected waves is determined by the temporal
variations of the local plasma parameters, caused by the flare heating and the
consequent cooling. We apply coronal seismology to both waves obtaining
estimations of the background plasma parameters.
