RECALCULATION OF H-L-ALPHA SKY SURVEYS - NO NEED FOR ANISOTROPIC SOLAR-WIND MASS OUTFLOWS - COMMENT

In a recently published paper, Scherer and Fahr (1995) claimed that th e departures of sky L alpha emission measured by Prognoz 5 and 6 from an optically thin model can be attributed entirely to deficiencies oft he optically thin approximation, and are not due to variations of sola r wind ionization rate with latitude, as advocated since many years by our research group. They base their claim on the result of their new sophisticated model of L alpha radiation transport. It is shown here t hat their new model, in the simple case of isotropic solar wind, predi cts a distribution of intensity in a simple geometry which is complete ly contradicted by the observations: they find a minimum of intensity near the upwind direction, where a maximum has been observed consisten tly by all La instruments. Therefore, their conclusion based on an err oneous model must be rejected.