Coexistence of Slow Magnetoacoustic Waves and Thermal Limit Cycles in a Coronal Bright Point

Coronal bright points (BPs) are clusters of small-scale loops ubiquitous on the solar surface observed in extreme ultraviolet (EUV) and X-ray wavelengths. We analyse characteristics of oscillations in EUV emissions observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) that are potentially due to different mechanisms. Our analysis method includes spatial morphological segmentation and running FFT techniques. For 37 regions of interest within a BP, the mean intensity of 171Å and 193Å EUV emissions are used to estimate the temperature and electron number density of the coronal plasma as a function of time, which exhibit oscillatory behaviour. We detect and analyse 792 oscillation events with periods ranging from 3 to 240 min. We observe spatial coherence across regions and find, with increasing periodicity, collective behaviour on a spatial scale larger than an individual region. We study the phase differences between the two AIA light curves and between temperature and density. Based on phase relations and forward modeling, we find that oscillations with periods up to around 5 min and ≳ 10 min are likely associated with slow magnetoacoustic waves and thermal limit cycles, respectively. Time-distance maps along an oscillation region reveal counter-propagating short-period waves propagating at acoustic speeds and long-period waves at a speed an order of magnitude slower. The simultaneity of oscillations over the range of periods suggests the coexistence of the two types of oscillatory processes in BPs.