High-frequency Wave Power Observed in the Solar Chromosphere with IBIS and ALMA

We present observational constraints on the chromospheric heating contribution from acoustic waves with frequencies between 5 and 50 mHz. We use 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 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, and plage). In order to disentangle the vertical versus transverse Alfvenic 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. This is in contrast to previous publications.

Automated summary

Observational constraints and synthetic observables are used to study the heating contribution of acoustic waves in the chromosphere. Results indicate that acoustic waves carry insufficient energy flux to maintain the quiet chromosphere.