The Horizontal Poynting Flux in the Solar Photosphere

Suzana S. A. Silva

Hosted by Plasma Dynamics Group, University of Sheffield, United Kingdom on June 9, 2022


A crucial step for understanding the origin of the high temperatures in the upper atmosphere is an accurate description of the energy transport. Current studies on the energy flux in the solar atmosphere mainly focus on the vertical electromagnetic flow through the photosphere, ignoring the possible Poynting flux’s contributions to local heating. This study used observational data from Sunrise/IMaX and Bifrost simulations to analyse the electromagnetic energy flux of the lower atmosphere. Based on a simulated quiet Sun atmosphere, we found that only a small fraction of the Poynting energy flows upwards in the photosphere. Most of the electromagnetic energy flows parallel to the surface, and it is mainly concentrated in small regions in the intergranular lanes. We derived an approximation for the horizontal Poynting flux - based only on the line-of-sight magnetic field and the horizontal velocity, variables that can be promptly retrieved from observations. Our proxy for the horizontal portion of the Poynting flux provides a similar distribution to the total electromagnetic flux, especially in regions with high levels of electromagnetic energy. To validate the findings, we also analysed the Sunrise/IMaX data. First, we confirmed that Bifrost data realistically describe photospheric quiet-Sun regions as its data have similar horizontal and line of sight magnetic field distributions compared to the observational data. Based on our proxy, we found very similar horizontal Poynting flux distributions for the observational data and simulated photosphere, with the electromagnetic energy flux reaching 1010 ergs cm−2 s−1. Compared to previous observational estimates of the vertical Poynting flux, the horizontal component of the Poynting flux is considerably more significant than the vertical component. Those findings corroborate that the electromagnetic energy flux in the photosphere is mainly parallel to the solar surface and can be properly described by our proxy for Poynting flux.

Recorded video