WEBJun 22, 2022 · Lorenz equations. Lorenz system. The system of equations. $$ \begin {eqnarray*} \dot x &=& -\sigma x+\sigma y, \\ \dot y &=& rx-y-xz, \\ \dot z &=& -bz+xy. \end {eqnarray*} $$. It arises as the $3$-mode truncation of the two-dimensional convection equations for parallel horizontal walls at constant, but different, temperatures.