The effects of magnetic fields on observational signatures of atmospheric escape in exoplanets: Double tail structures

Using 3D radiative MHD simulations and Lyman-$\alpha$ transit calculations, we investigate the effect of magnetic fields on observational signatures atmospheric escape in exoplanets. same stellar wind, vary planet's dipole field strength ($B_p$) from 0 to 10G. For $B_p<3$G, structure escaping atmosphere begins break away a comet-like tail following planet ($B_p=0$), as see more absorbing material above below orbital plane. $B_p\geq3$G, find ``dead-zone'' around equator, where low velocity is trapped closed lines. The dead-zone separates two polar outflows escapes along open lines, leading double structure, We demonstrate that magnetised planets occurs through outflows, opposed predominantly night-side non-magnetised models. small increase rate with $B_p$, though this should not affect timescale loss. As size increases so does line centre absorption Lyman-$\alpha$, low-velocity neutral hydrogen covers disc during transit. $B_p<3$G blue wing decreases, less funnelled sight by wind. In red (and for $B_p>3$G wing) caused growing volume magnetosphere. Finally show transits mid-disc differ asymmetry structure.