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There is increasing evidence that the highly ionized multiphase components ofAGN disk winds may be due to thermal instability. The ions responsible forforming the observed X-ray absorption lines may only exist in relatively coldclumps that can be identified with the so-called 'warm absorbers'. Here wecalculate synthetic absorption lines for such warm absorbers from firstprinciples by combining 2D hydrodynamic solutions of a two-phase medium with adense grid of photoionization models to determine the detailed ionizationstructure of the gas. Our calculations reveal that cloud disruption, whichleads to a highly complicated velocity field (i.e. a clumpy flow), will onlymildly affect line shapes and strengths when the cold gas becomes highly mixedbut not depleted. Prior to complete disruption, clouds which are optically thinto the driving UV resonance lines will cause absorption at an increasinglyblueshifted line of sight velocity as they are accelerated. This behavior willimprint an identifiable signature on the line profile if warm absorbers areenshrouded in an even broader absorption line produced by a high column ofintercloud gas. Interestingly, we show that it is possible to develop aspectral diagnostic for cloud acceleration by differencing the absorptioncomponents of a doublet line, a result which can be qualitatively understoodusing a simple partial covering model. Our calculations also permit us tocomment on the spectral differences between cloud disruption and ionizationchanges driven by flux variability. Notably, cloud disruption offers anotherpossibility for explaining absorption line variability.

Synthetic absorption lines for a clumpy medium: a spectral signature for cloud acceleration in AGN?