Rocket observations and modelling of flux-tubes

The solar observations at high angular resolution have led to the discovery that the solar magnetic field is structured in filamentary fields at the photospheric level. Manifestations of these fluxtubes can be diagnosed with EUV images (with the Transition Region Camera Rocket Experiment, TRC) at 220nm in the middle photosphere, at 160nm in the temperature minimum region or in the Ly alpha and C IV lines formed at temperatures 20 000K and 100 000K in the transition region. In the frame of a thin flux tube modelling of the TRC data, the vertical variation of tube parameters and the conditions for thermalisation in the upper photosphere are discussed. We consider constraints from EUV observations on current models of flux-tubes and coronal loops including non LTE calculations, dynamic and magnetic effects.