DOT Tomography of the Solar Atmosphere VII. Chromospheric Response to Acoustic Events

TL;DR

This study investigates how the solar chromosphere responds to acoustic events in the photosphere using multi-wavelength observations, revealing detailed interactions and the importance of Halpha data for chromospheric analysis.

Contribution

It provides a comprehensive diagnostic approach combining multiple data types to analyze chromospheric responses to photospheric acoustic events, highlighting the significance of Halpha observations.

Findings

Chromosphere visibility is best in Halpha data.

Acoustic grains are linked to shock excitation and magnetic features.

Fibril buffeting correlates with Doppler shifts in chromospheric response.

Abstract

We use synchronous movies from the Dutch Open Telescope sampling the G band, Ca II and Halpha with five-wavelength profile sampling to study the response of the chromosphere to acoustic events in the underlying photosphere. We first compare the visibility of the chromosphere in Ca II H and Halpha, demonstrate that studying the chromosphere requires Halpha data, and summarize recent developments in understanding why this is so. We construct divergence and vorticity maps of the photospheric flow field from the G-band images and locate specific events through the appearance of bright Ca II H grains. The reaction of the Halpha chromosphere is diagnosed in terms of brightness and Doppler shift. We show and discuss three particular cases in detail: a regular acoustic grain marking shock excitation by granular dynamics, a persistent flasher which probably marks magnetic-field concentration, and an exploding granule. All three appear to buffet overlying fibrils, most clearly in Dopplergrams. Although our diagnostic displays to dissect these phenomena are unprecedentedly comprehensive, adding even more information (photospheric Doppler tomography and magnetograms, chromospheric imaging and Doppler mapping in the ultraviolet) is warranted.