| Astrophysics (Index) | About |
The Jeans parameter is a measure of an atmosphere's gas particles' tendency to escape (atmospheric escape) through a thermal escape mechanism (Jeans escape or hydrodynamic escape). It is a ratio of the gravitational potential energy of the particles to their kinetic energy. In a (virtually) spherically-symmetric situation, it is a function of distance from the center of the body. The smaller the Jeans parameter, the more likely the escape, and thresholds have been devised to indicate whether such escape is a significant possibility.