| modified index of refraction [`mäd·ǝ´fīd `in´deks ǝv ri`frak·shǝn] METEOROLOGY An atmospheric index of refraction mathematically modified so that when its gradient is applied to energy propagation over a hypothetical flat earth, it is substantially equivalent to propagation over the true curved earth with the actual index of refraction. Also known as modified refractive index; refractive modulus. |