Paper detail

Propagation of Waves above a Plage as Observed by IRIS and SDO

Context. MHD waves are proposed to transport sufficient energy from the photosphere to heat the transition-region (TR) and corona. However, various aspects of these waves such as their nature, propagation characteristics and role in the atmospheric heating process remain poorly understood and are a matter of further investigation. Aims. We aim to investigate wave propagation within an active-region (AR) plage using IRIS and AIA observations. The main motivation is to understand the relationship between photospheric and TR oscillations. We plan to identify the locations in the plage region where magnetic flux tubes are essentially vertical, and further our understanding of the propagation and nature of these waves. Methods. We have used photospheric observations from AIA (i.e., AIA 1700 Å) as well as TR imaging observations (IRIS/SJI Si iv 1400.0 Å). We have investigated propagation of the waves into the TR from the photosphere using wavelet analysis (e.g., cross power, coherence and phase difference) with inclusion of a customized noise model. Results. Fast Fourier Transform(FFT) shows the distribution of wave power at photospheric & TR heights. Waves with periods between 2.0- and 9.0-minutes appear to be correlated between the photosphere and TR. We exploited a customized noise model to estimate 95% confidence levels for IRIS observations. On the basis of the sound speed in the TR and estimated propagation speed, these waves are best interpreted as the slow magneto acoustic waves (SMAW). It is found that almost all locations show correlation/propagation of waves over broad range of period from photosphere to TR. It suggests the wave's correlation/propagation spatial occurrence frequency is very high within the plage area.