Equatorial deformation radius
= Equatorial deformation radius
{title2=$R_{\rm eq}=\sqrt{c/\beta}$}
For an equatorial <beta plane> and a <shallow water> wave speed $c$, the natural meridional trapping scale is $R_{\rm eq}=\sqrt{c/\beta}$. A decaying <equatorial Kelvin wave> has $\eta\propto e^{-y^2/(2R_{\rm eq}^2)}$. An envelope written $e^{-y^2/L^2}$ instead uses $L=\sqrt2R_{\rm eq}$; stating the exponent convention prevents a factor-of-two error in the meridional <Cauchy momentum equation>.