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Paper: Chromospheric Heating and Low-Chromosphere Modeling
Volume: 368, The Physics of Chromospheric Plasmas
Page: 499
Authors: Fontenla, J.M.; Balasubramaniam, K.S.; Harder, J.
Abstract: Updated modeling of the “quiet” Sun low chromosphere based on existing observations show that at least all the data we examined in detail is consistent with a single model that has a very low temperature minimum and a sharp temperature increase above it. Such a model explains simultaneously the deep CO lines observed on the disk and off the limb, as well as the UV and radio continua and thus solves the controversy regarding the minimum temperature without resorting to “bifurcation”. This results simply from considering both: the spatial extent of the intensity contribution functions, and non-LTE. The model also shows that the structure of the low-chromosphere cannot be unambiguously inferred from any simple diagnostic but rather needs to be examined by forward modeling with consideration of full-NLTE radiative transfer and observations at many wavelengths. In addition, the characteristics of this model are consistent with the magnetic heating of the chromosphere. The mechanism proposed consists of small scale magnetic fields and sudden triggering of their free-energy dissipation by a plasma instability starting at the base of the chromospheric plateau. As a result of such a mechanism a complex spatial structure would result in the upper chromosphere that can hardly be explained in terms of shocks but instead shows magnetic patterns.
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