Forward Modelling of Coronal Intensity Perturbations
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In this paper, forward modelling is used to investigate the relation between given temperature and density perturbations and the resulting (synthesised) intensity perturbations, as would be observed by, e.g., TRACE and EIS (onboard Hinode). Complex and highly non-linear interactions between the components which make up the intensity (density, ionisation balance and emissivity) mean that it is non-trivial to reverse this process, i.e., obtain the density and temperature perturbations associated with observed intensity oscillations. In particular, it is found that the damping rate does not often ‘survive’ the forward modelling process, highlighting the need for a very careful interpretation of observed (intensity) damping rates. With a few examples, it is demonstrated that in some cases even the period of the oscillations can be altered and that it is possible for two different sets of input temperature and density to lead to very similar intensities (the well-known ‘ill-posed’ inversion process).
KeywordsMHD: oscillations – corona – activity
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