In the radiative zone, energy from the core slowly travels outward. This region is so dense that the Sun's energy takes about 150,000 years to work its way through
Space Science Institute (SSI),Space Weather Center, Glossary of Space Weather-Related Terms, Colorado, USA 2011. http://www.spaceweathercenter.org/glossary/001/01. html, (Space Wthr - Amer) {860}