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Solar flares are amongst the most energetic events in our solar system. Generally seen as intense brightenings in the UV and X-ray domains, they also inject solar energetic particles and coronal mass ejections (CMEs) into the interplanetary medium. Their effects on the space environment of planets are non-negligible, with the known consequences on human activities. A better understanding of the processes taking place during flares is needed in order to develop future prediction capacities.
In the last decades, the wealth of data from space and ground missions as well as developments of numerical models have provided a deeper knowledge of the behaviour of magnetic fields during solar flares. From flux ropes to flare loops, from electric currents to flare ribbons, we will see how both observations and modelling help bring together a generic 3D picture of the mechanisms taking place prior and during solar flares. The evolution of different magnetic structures, well reproduced with a magnetohydrodynamic (MHD) model, is dictated by magnetic reconnection, which converts magnetic energy stored in the Sun's corona. In particular, consequences of magnetic reconnection can be seen in the different layers of the solar atmosphere, which allows us to go back to its intrinsic properties in 3D. We will then show that while 3D MHD models are mostly focussed on the behaviour of the magnetic field due to the low-beta condition of the corona, spectroscopic observations can come in handy when completing the cartoon with the plasma behaviour. We will discuss how such observations of flaring regions (heating, kernel brightening, ribbons, plasma velocities) help us getting a better understanding of flares throughout the different layers of the Sun's atmosphere. Furthermore, in the context of Solar Orbiter, we will see how the multi-instrument mission will provide a great opportunity to better constraint our models, by providing observations in quadrature with other missions, by joining remote-sensing and in situ diagnostics, and by complementing other missions dedicated to our Sun. |