A computational model for irradiance on close-in planetary systems

Abstract: There is something about inverse-square laws that makes them fail at extremities. The inverse-square law, which is used commonly in studying the irradiance on exoplanets fails at the extreme case of planets closer than 0.01 AU. Therefore, in order to correctly predict possible climate states of such systems, we need a new model which accurately calculates angles subtended by various surface elements and integrate the generalized equation. A direct consequence of such a model is the shift of the terminator about 20 degrees beyond the poles. The irradiance at the poles is about 100-200 kW/m2 higher than what is predicted by the inverse-square law. This work therefore becomes crucial because it underscores the need to modify the current GCM models. The error in the numerical integration values of irradiance is less than one percent making our estimate very reliable.