High-frequency wave power observed in the solar chromosphere with IBIS and ALMA

TL;DR

This study measures high-frequency acoustic wave power in the solar chromosphere using IBIS and ALMA, revealing that these waves carry insufficient energy to sustain the quiet chromosphere, challenging prior assumptions.

Contribution

It provides new observational constraints on chromospheric heating by acoustic waves, combining multi-instrument data and synthetic modeling to quantify energy flux.

Findings

Acoustic waves carry up to 1 kW/m² of energy flux in the middle chromosphere.

Power spectra follow a power law, varying with solar feature type.

Acoustic waves are insufficient to maintain the quiet chromosphere.

Abstract

We present observational constraints on the solar chromospheric heating contribution from acoustic waves with frequencies between 5 and 50 mHz. We utilize observations from the Dunn Solar Telescope in New Mexico complemented with observations from the Atacama Large Millimeter Array collected on 2017 April 23. The properties of the power spectra of the various quantities are derived from the spectral lines of Ca II 854.2 nm, H I 656.3 nm, and the millimeter continuum at 1.25 mm and 3 mm. At the observed frequencies the diagnostics almost all show a power law behavior, whose particulars (slope, peak and white noise floors) are correlated with the type of solar feature (internetwork, network, plage). In order to disentangle the vertical versus transverse plasma motions we examine two different fields of view; one near disk center and the other close to the limb. To infer the acoustic flux in the middle chromosphere, we compare our observations with synthetic observables from the time-dependent radiative hydrodynamic RADYN code. Our findings show that acoustic waves carry up to about 1 kW m$^{-2}$ of energy flux in the middle chromosphere, which is not enough to maintain the quiet chromosphere, contrary to previous publications.