Magnetohydrodynamic Poynting Flux Vortices in the Solar Atmosphere and Their Role in Concentrating Energy

Abstract

The nature of energy generation, transport, and effective dissipation responsible for maintaining a hot solar upper atmosphere is still elusive. The Poynting flux is a vital parameter for describing the direction and magnitude of the energy flow, which is mainly used in solar physics for estimating the upward energy generated by photospheric plasma motion. This study presents a pioneering 3D mapping of the magnetic energy transport within a numerically simulated solar atmosphere. By calculating the Finite Time Lyapunov Exponent of the energy velocity, defined as the ratio of the Poynting flux to the magnetic energy density, we precisely identify the sources and destinations of the magnetic energy flow throughout the solar atmosphere. This energy mapping reveals the presence of transport barriers in the lower atmosphere, restricting the amount of magnetic energy from the photosphere reaching the chromosphere and corona. Interacting kinematic and magnetic vortices create energy channels, breaking through these barriers and allowing three times more energy input from photospheric motions to reach the upper atmosphere than before the vortices formed. The vortex system also substantially alters the energy mapping, acting as a source and deposition of energy, leading to localized energy concentration. Furthermore, our results show that the energy is transported following a vortical motion: the Poynting flux vortex. In regions where these vortices coexist, they favor conditions for energy dissipation through ohmic and viscous heating, since they naturally create large gradients in the magnetic and velocity fields over small spatial scales. Hence, the vortex system promotes local plasma heating, leading to temperatures around a million Kelvins.

Comprehensive Synthesis of Magnetic Tornado: Cospatial Incidence of Chromospheric Swirls and Extreme-ultraviolet Brightening

“…During the analyzed period, a magnetic tornado is generated by photospheric vortex flows, which is the same triggering mechanism as presented in many previous simulations (Kuniyoshi et al 2023;Silva et al 2024). The lifetime of the magnetic tornado is approximately   ( ) t 10 minutes 950 s 1550 s , corresponding to that of the photospheric vortex, which persists for about one granular turnover time.…”

“…Magnetic tornadoes, identified as impulsive Alfvén waves originating from photospheric vortex motions within intergranular lanes (Wedemeyer-Böhm et al 2012;Battaglia et al 2021), display signatures observed in the photosphere or chromosphere, manifesting as swirling plasma motions (diameter ∼2 Mm; Shetye et al 2019;Dakanalis et al 2022). Magnetoconvection simulations focusing on the quiet Sun have indicated that magnetic tornadoes can contribute approximately 50% of the total Poynting flux into the corona (Kuniyoshi et al 2023;Silva et al 2024).…”