Can instrumental effects obscure the true photospheric wave spectrum?

TL;DR

This study investigates how optical aberrations and resolution limitations in solar observations can distort the observed wave spectra, emphasizing the importance of high-resolution data for accurate interpretation of solar atmospheric dynamics.

Contribution

The paper provides the first detailed analysis of how instrumental resolution affects the observed wave spectra in solar features, highlighting potential underestimations in wave energy reports.

Findings

Degradation of resolution shifts dominant frequency from 5 to 3 mHz.

Straylight contamination increases with lower resolution, masking true oscillations.

High-resolution instruments are crucial for accurate solar wave analysis.

Abstract

Optical aberrations and instrument resolution can affect the observed morphological properties of features in the solar atmosphere. However, little work has been done to study the effects of spatial resolution on the dynamical processes occurring in the Sun's atmosphere. In this work, owing to the availability of high-resolution observations of a magnetic pore captured with the Interferometric BIdimensional Spectrometer mounted at the Dunn Solar Telescope, we studied the impact of the diffraction limit and the sampling of an instrument on line-of-sight Doppler velocity oscillations. We reported a noticeable shift in the dominant frequency band from $5$ to $3$ mHz, as both the angular and detector resolutions of the instruments were degraded. We argue that the observed behaviour is a result of the increased contamination of straylight from neighbouring quiet Sun regions, masking the true behaviour of umbral oscillations. These results suggest that the wave energy contributions reported in the literature and based on low-resolution instrumentation may be fundamentally underestimated. As we move into the era of high-resolution instrumentation such as DKIST and MUSE, this work will offer a critical baseline for interpreting new observations, especially in terms of distinguishing true dynamic behaviours from artefacts introduced by instrument-related limitations.