The importance of horizontal Poynting flux in the solar photosphere

Abstract

The electromagnetic energy flux in the lower atmosphere of the Sun is a key tool to describe the energy balance of the solar atmosphere. Current investigations on energy flux in the solar atmosphere focus primarily on the vertical electromagnetic flux through the photosphere, ignoring the Poynting flux in other directions and its possible contributions to local heating. Based on a realistic Bifrost simulation of a quiet-Sun (coronal hole) atmosphere, we find that the total electromagnetic energy flux in the photosphere occurs mainly parallel to the photosphere, concentrating in small regions along intergranular lanes. Thereby, it was possible to define a proxy for this energy flux based on only variables that can be promptly retrieved from observations, namely, horizontal velocities of the small-scale magnetic elements and their longitudinal magnetic flux. Our proxy accurately describes the actual Poynting flux distribution in the simulations, with the electromagnetic energy flux reaching $10^{10}$ erg\,cm${}^{-2}$\,s${}^{-1}$. To validate our findings, we extended the analysis to SUNRISE/IMaX data. First, we show that Bifrost realistically describes photospheric quiet-Sun regions, as the simulation presents similar distributions for line-of-sight magnetic flux and horizontal velocity field. Second, we found very similar horizontal Poynting flux proxy distributions for the simulated photosphere and observational data. Our results also indicate that the horizontal Poynting flux in the observations is considerably larger than the vertical electromagnetic flux from previous observational estimates. Therefore, our analysis confirms that the electromagnetic energy flux in the photosphere is mainly horizontal and is most intense in localized regions along intergranular lanes.

14 pages, 8 figures Accept for publication in ApJ

References in corpus (7)

• Solar Magnetic Tracking. I. Software Comparison and Recommended Practices
• The horizontal internetwork magnetic field: numerical simulations in comparison to observations with Hinode
• A Comprehensive Method of Estimating Electric Fields from Vector Magnetic Field and Doppler Measurements
• Simulations Show that Vortex Flows could Heat the Chromosphere in Solar Plage
• The Alfvénic nature of chromospheric swirls
• Inclinations of small quiet-Sun magnetic features based on a new geometric approach
• The coronal energy input from magnetic braiding

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