Can High Frequency Acoustic Waves Heat the Quiet Sun Chromosphere?

TL;DR

This study investigates whether high frequency acoustic waves can heat the quiet Sun chromosphere, finding that their energy flux is insufficient for significant heating.

Contribution

It provides high-resolution measurements showing that acoustic wave power is too low to account for chromospheric heating in the quiet Sun.

Findings

Integrated acoustic power is only slightly higher at full resolution.

Acoustic flux is less than 800 W/m², insufficient for chromospheric heating.

High frequency waves do not dominate the energy budget.

Abstract

We use Hinode/SOT Ca II H-line and blue continuum broadband observations to study the presence and power of high frequency acoustic waves at high spatial resolution. We find that there is no dominant power at small spatial scales; the integrated power using the full resolution of Hinode (0.05'' pixels, 0.16'' resolution) is larger than the power in the data degraded to 0.5'' pixels (TRACE pixel size) by only a factor of 1.2. At 20 mHz the ratio is 1.6. Combining this result with the estimates of the acoustic flux based on TRACE data of Fossum & Carlsson (2006), we conclude that the total energy flux in acoustic waves of frequency 5-40 mHz entering the internetwork chromosphere of the quiet Sun is less than 800 W m$^{-2}$, inadequate to balance the radiative losses in a static chromosphere by a factor of five.