Introduction

We use the cyclotron model developed by Potter et al (1997) who used the calculations of Meggitt and Wickramasinghe (1982) to model cyclotron emission from the shock region in MCVs. Using this model it is possible to make a gross fit to the polarized observations of MCVs by making assumptions on the shape of the accretion region.
Recently Cropper and Horne (1994) used the maximum entropy method to map the spatial extent of the X-ray and optical emission (photometric only)in the AM Her system ST LMi. However they assumed that the optical emission is isotropic which is not the case for cyclotron radiation.
We use a Genetic Algorithm (GA) for the first stage in optimising the model fit to the data. By selectively breeding the best solutions a more robust global fit is obtained compared to the more traditional methods.
When the GA has found the best global minimum we use the more traditional Powells method (a successive line minimisation routine) to refine the best solution.
Modified Tikhonov regularisation is used to ensure realistic solutions.
This method has been successful in reproducing the test emission regions from the test polarized light curves.

Stephen Potter
Thu Jul 31 14:44:15 BST 1997

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