A thin → transition → layer inside → Sun, between the → differentially rotating → convection zone and the uniformly rotating radiative interior. Discovered through → helioseismology, it has raised considerable interest, but its thinness remains still to be explained. Due to its strong → shear, it is believed to play a crucial role in the generation of the → solar magnetic field.
Tachocline, from tacho- a combining form meaning "speed," → tachyon + → -cline "slope." The term was first coined by Edward A. Spiegel and Jean-Paul Zahn (1992, A&A 265, 106), by analogy to the oceanic → thermocline.