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Eclipses are very favourable for the photosphere- chromosphere and coronainterface observation as the occultation takes place in space, free ofparasitic light coming from the occulting disk (the Moon). Independently, EUVfiltergrams of the limb region obtained in space were analyzed using onedimensional hydrostatic VAL models but this method ignores the ubiquitousmagnetic field emergence phenomenon associated with the chromospheric network.A jump of temperature from 0.01 to 1 MK is observed near the 2 Mm heights andhigher, further producing a permanent solar wind flow. The heating processesresponsible for this temperature jump and for the flow are not yet fullyunderstood. In this thesis, we reconsider these problems with new high cadenceCCD flash spectra, white light (W-L) eclipse images and new EUV images obtainedwith space-borne instruments. We illustrate the mechanisms of low FirstIonisation Potential (FIP) emission lines present in the low layers of thesolar atmosphere, and nearby prominences. We characterize in detail the Heshells and the solar interface region.  Main results: i) The solar edge and the temperature bifurcation:structuration and discussion of the analysed low FIP lines and the truecontinuum in the 400 to 600 km heights above the limb, emission mechanisms; ii)Visible mesospheric and chromospheric emission lines in the interface regionsincluding the Paschen alpha HeII line starting at 800 km above the limb,produced by photo-ionisation showing shells around the Sun and probing theprominence-corona interface; iii) The contribution of small scale dynamicalspicules and macro-spicules starting at 1 Mm above the limb showing that the 1Dhydrostatic stratified models are not adapted to the upper layers.

The solar interface from the photosphere to the chromosphere and corona : contribution of eclipses and EUV filtergrams