RESOLVE · REalistic Simulations and ObservationaL Validation of small-scale Energy channels on the Sun

REalistic Simulations and ObservationaL Validation of small-scale Energy channels on the Sun

The origin of the million Kelvin hot tenuous atmosphere of the Sun, the corona, surrounding the cooler 6000 K photosphere is a long-standing puzzle in modern-day solar and stellar astrophysics. The mechanisms responsible for coronal heating also plays a crucial role in the production of large flares and the acceleration of solar wind, both of which influence the space weather and the Sun-Earth connection. Solar coronal observations in the extreme ultraviolet (EUV) and X-rays reveal loop-like structures of hot plasma confined by the magnetic field. One key to solving the puzzle of the hot corona is understanding the mass and energy transfer through the solar atmosphere in these loops. The magnetic energy required to heat the coronal loops is generated by convective motions beneath the solar surface and then transported through the photosphere into the corona where it is dissipated. The details of how, and at which spatial and temporal scales, the Poynting flux is transported through the solar surface are not well understood. The objective of the project was to characterize the nature of energy transfer from the photosphere at small spatial scales by combining state-of-the-art observations and three-dimensional (3D) radiation magnetohydrodynamic (MHD) simulations. The main outcome of the action is two-fold. (1) By analyzing a variety of observations, we identified that coronal loops often have a complex magnetic topology at their footpoints. This complex topology is driven by transient events of granular-scale magnetic flux emergence and cancellation at the feet of coronal loops. These transient events result from the magnetoconvection near the photosphere. Our MHD simulations reproduced such magnetic transients and predicted that they persist on even smaller spatial scales than what the current photospheric observation resolution of ~100 km. (2) Our observations and simulations strongly suggest that the energy liberated during the reconnection of magnetic field associated with flux emergence and cancellation plays a crucial role in energizing the coronal loops. In conclusion, the action successfully achieved its objectives by revealing new details of the photosphere-corona connection and of the nature of magnetic energy release that it likely responsible for the coronal heating.

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