Assessment of DKIST/VTF capabilities for the detection of local acoustic source wavefronts

Abstract

Introduction – Recent studies have demonstrated that temporal filtering can successfully identify local acoustic source wavefronts in radiative magnetohydrodynamic simulations of the solar photosphere. Extending this capability to observations promises new insight into the stochastic excitation of solar p-modes, the source depth distribution below the photosphere, and the dominant physical processes underlying acoustic wave excitation. Such measurements would also enable improved characterization of the complex wavefield in the lower chromosphere and open the possibility of ultra-local helioseismic diagnostics. Methods – In this work, we assess an observational strategy for the detection of local acoustic wavefronts on the Sun using the Visible Tunable Filter (VTF) instrument on the National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST). Because wavefront identification requires high spatial and temporal resolution and is limited by the small amplitudes of the wave perturbations, we focus on identifying specific wavelength combinations within photospheric spectral lines that maximize the sensitivity to the wave signal. Results – Under the cadence and spectral resolution constraints of DKIST/VTF observations and for the particular simulated wavefront we examine, this approach suggests two possible strategies: fast monochromatic imaging at 6302.425 Å, or ordered interleaved observations in the blue wing of either the Fe I 6302.5 Å or Fe I 5250.6 Å line (between 6302.419 Å and 6302.465 Å, or between 5250.579 Å and 5250.607 Å respectively). Discussion – The observational capabilities of DKIST/VTF satisfy the stringent spatial, spectral, and temporal resolution requirements of the methods suggested here. Thus, DKIST/VTF presents an opportunity to detect local acoustic wavefronts in the photosphere at their intrinsic temporal and spatial scales for the first time.