Interaction phenomena between atmospheric layers in planetary atmospheres give rise to highly complex exchanges influencing thermal structure, composition and dynamics. In particular, the question of hydrodynamic escape in exoplanet atmospheres is a key issue for quantifying the mass loss in these atmospheres. Short-period exoplanets subject to violent interactions with their host star are particularly sensitive to these effects [1,2]. The scientific program presented here called AETHER (Atmospheric Escape and Transfer phenomena in Heated Exoplanets by stellar Radiation) combining modelling and future observations is a continuation of a pioneer work connecting lower and upper atmospheric modelling in exoplanets [3].In order to address these questions, a model is presented combining energy deposition (itself constrained by XUV emissions from the parent star), the chemistry induced in an atmosphere of hydrogen, helium and heavier elements, and dynamical redistribution to go beyond one-dimensional models. The objective of the model is to characterize observables in exoplanets spectroscopy, in order to adapt the model to real observations, and to constrain in fine the atmospheric escape. Observables to characterize these phenomena include Ly-α lines (observable from space, but perturbed by reabsorption from the interstellar medium), metallic lines [4], and more recently the He-I [5,6,7] which coupled with observations of the H-α line has enabled advances on the models [8,9]. An atmospheric radiative transfer model incorporating the predictions of the energy deposition model [10] completes the atmospheric modeling towards the lower atmospheric levels. Models for the He I triplet at 1.083µm have been scaled to the well described planet HD 209458b. Assuming a He absorption taken from Carmenes analysis [11], line intensities can be predicted for observations by high resolution spectroscopy. Different planets have been studied for higher XUV fluxes and escape mass, like in HAT-P-11b [3, 6]. For still higher irradiation, like on HAT-P-32b [5,12] the detectability would be more easily ensured. In addition to these lines, the simulation has focused on the detectability of hydrogen quadrupole lines : H2 lines in 1-0 and 2-0 bands at 2.3 and 1.15 µm respectively are modelled in the radiative transfer simulation. These transitions have been detected on Jupiter [13] in particular conditions, as in the auroral regions. Detecting direct H2 transitions would not be only a textbook achievement in the study of exoplanets, but would pave the way for direct measurement of the atmospheric temperatures at their pressure level of formation (typically ~100 mbar in transit spectroscopy in H filter, for the 2-0 vibrational band of H2). In addition to the normal atmosphere calculations, a probable upper atmosphere heating, would enhance the possibility to detect H2 by populating the upper transitional levels by analogy with Jupiter [14]. Targets for future observations of exoplanets are in the class of hot (super)Neptunes, with "puffy" atmospheres and large atmospheric scale heights. A good template for the simulations would be the planet WASP-193b [2]. This planet is particularly intriguing as a low-density Super-Neptune, described in the discovery paper as "an exquisite target for characterization by transmission spectroscopy." With a Transmission Spectroscopy Metric (TSM) of approximately 600, WASP-193b ranks as the fourth highest among all known exoplanets, making it a prime candidate for atmospheric studies. The full list of parameters of WASP-193b can be obtained from [2], the most important being a radius R~1.463 RJup, an equilibrium temperature Teq=1252 K and a mass Mp=0.141 MJup, leading to a density of 0.059 g.cm-3. The program AETHER will be developped in preparation for the Ariel mission - even if observations in this field are beyond the reach of its instruments, understanding and modeling them is a key element for a better knowledge of the chemistry of the lower atmosphere, the main target of Ariel observations. Figure caption : a) He line prediction: (case 0) equilibrium temperature 1252 K at 1 micro bar and solar abundance modified by Wasp-193 [Fe/H]; (case 1) boundary condition set by the lower atmosphere chemistry model, using the same SED for both regions (self-consistent). b) H2-q contribution predictionReferences[1] García Muñoz, A.; Fossati, L.; Youngblood, A.; Nettelmann, N.; Gandolfi, D.; Cabrera, J.; Rauer, H. A Heavy Molecular Weight Atmosphere for the Super-Earth π Men c. 2021ApJ...907L..36G[2] Barkaoui, Khalid et al. An extended low-density atmosphere around the Jupiter-sized planet WASP-193 b, (2024) NatAs, 8, 909B[3] Ben-Jaffel, Lotfi; Ballester, Gilda E.; García Muñoz, Antonio; Lavvas, Panayotis; Sing, David K.; Sanz-Forcada, Jorge; et al. Signatures of strong magnetization and a metal-poor atmosphere for a Neptune-sized exoplanet. (2022) NatAs, 6, 141.[4] Casasayas-Barris N. et al. Atmospheric characterization ofthe ultra-hot Jupiter MASCARA-2b/KELT-20b. Detection of CaII, FeII, NaI, and the Balmer series transit. spectroscopy. (2019) A&A, 628A, 9[5] Czesla, S. et al, Hα and He I absorption in HAT-P-32 b observed with CARMENES. Detection of Roche lobe overflow and mass loss (2022) A&A, 657A, 6[6] Allart, R. et al. Spectrally resolved helium absorption from the extended atmosphere of a warm Neptune-mass exoplanet (2018) Science, 362, 1384[7] Masson A. et al. Probing atmospheric escape through metastable He I triplet lines in 15 exoplanets observed with SPIRou. (2024) Astronomy & Astrophysics, Volume 688, A179. [8] Lampon, M.et al. 2023. Characterisation of the upper atmospheres of HAT-P-32b. A&A 673 A140[9] Sanz-Forcada, et al. Connection between planetary He I λ10 830 Å absorption and extreme-ultraviolet emission of planet-host stars. 2025A&A. 693A.285S[10] Arfaux, Anthony; Lavvas, Panayotis Coupling haze and cloud microphysics in WASP-39b's atmosphere based on JWST observations (2024) MNRAS, 530, 482A[11] Lampon, M. et al. Modelling the He I triplet absorption at 10 830 Å in the atmosphere of HD 209458 b. (2020) A&A, 636A, 13L. [12] Yan, D. et al. A possibly solar metallicity atmosphere escaping from HAT-P-32b revealed by Hα and He absorption (2024) A&A, 686A, 208[13] Kim, S.; Temperatures of the Jovian auroral zone inferred from 2-μm H2 quadropole line observations. (1990) Icarus, 84, 54.[14] Barthelemy, M. et al. H2 vibrational temperatures in the upper atmosphere of Jupiter. (2005) A&A, 437, 329