Wave Heating of the Solar Chromosphere

Molnar, Momchil Emil

Graduate Thesis Or Dissertation

Wave Heating of the Solar Chromosphere Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/0v8381821

Abstract

The solar chromosphere is well known to be in a radiative balance that requires an unac- counted source of heating. In this thesis I present observational constraints on the wave energy flux in the solar chromosphere, which is one of the favored chromospheric heating mechanisms. We employ chromospheric diagnostics ranging from the ultraviolet through the optical to the millimeter parts of the spectrum. We explore the formation mechanism of the millimeter solar continuum radiation first. We find that out-of-statistical equilibrium electron density determines its interpretation. We constrain the observed wave fluctuations in the solar atmosphere with cotemporal observations with the Atacama Large Millimeter Array (ALMA) and optical data from the Dunn Solar Telescope (DST). We combine these data with radiative hydrodynamic modeling with the RADYN code and find that the derived estimate for the acoustic wave energy flux is insufficient to maintain the radiative output of the solar chromosphere. Next we extend our work to higher layers in the solar atmosphere, by using the Interface Region Imaging Spectrograph (IRIS). We ex- amine the acoustic flux in the upper chromosphere and find that acoustic waves are most probably not maintaining the chromosphere and the corona in their thermal state based on the estimates from advanced 3D Bifrost simulations. We also examine the center-to-limb variation of the velocity fluctuations observed with IRIS in order to constrain the transverse amplitudes in the solar chromosphere, which is an important input into coronal and chromospheric heating models. The signatures of transverse wave fluctuations in our analysis can serve as a spectroscopic constraint on the amplitudes of Alfv ́en waves in the solar chromosphere. In the last chapter we describe future avenues to extend our understanding of wave propagation in the solar atmosphere.

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