A chromospheric conundrum?

Abstract

We examine spectra of the Ca II H line, obtained under good seeing conditions with the VTT Echelle Spectrograph in June of 2007, and higher resolution data of the Ca II 8542 Angstrom line from Fabry-Perot instruments. The VTT targets were areas near disk center which included quiet Sun and some dispersed plage. The infrared data included quiet Sun and plage associated with small pores. Bright chromospheric network emission patches expand little with wavelength from line wing to line center, i.e. with increasing line opacity and height. We argue that this simple observation has implications for the force and energy balance of the chromosphere, since bright chromospheric network emission is traditionally associated with enhanced local mechanical heating which increases temperatures and pressures. Simple physical considerations then suggest that the network chromosphere may not be able to reach horizontal force balance with its surroundings, yet the network is a long-lived structure. We speculate on possible reasons for the observed behavior. By drawing attention to a potential conundrum, we hope to contribute to a better understanding of a long-standing unsolved problem: the heating of the chromospheric network.

Accepted for publication in the Astrophysical Journal

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Cited by in corpus (5)

• Heating of the magnetic chromosphere: observational constraints from Ca II 8542 spectra
• Chromospheric diagnosis with Ca II lines: forward modeling in forward scattering (I)
• The energy of waves in the photosphere and lower chromosphere: IV. Inversion results of Ca II H spectra
• Chromospheric and Coronal Wave Generation in a Magnetic Flux Sheath
• Stratification of canopy magnetic fields in a plage region. Constraints from a spatially-regularized weak-field approximation method