Sambridge, MalcolmJackson, Andrew2015-12-132015-12-13August 7 2http://hdl.handle.net/1885/84395We discuss the problem of softening a hard quadratic bound to generate a personal prior probability distribution. The quadratic bound requires the model vector to live within a hyperspherical volume. Prior information suggests we may work in a finite-dimensional space, thus avoiding the known difficulties associated with infinite-dimensional spaces, and that values of the Euclidean 2-norm within the volume are uniformly distributed. The application is to the estimation of the magnetic field at the core-mantle boundary.Keywords: Bound softening; Earth's magnetic field200510.1063/1.21498312015-12-12