Planetary-scale nonlinear MHD excitation in quasi-2D ionosphere from the first principles

Abstract A new model of planetary-scale nonlinear magnetohydrodynamic excitations (PMHDE) has been developed for the F-region of the ionosphere. The model preserves the original MHD equations without introducing additional curl operations and accounts for meridional gradients in both Earth’s rotation and the geomagnetic field. For the first time, it consistently incorporates conductivity nonlinearity and geomagnetic field inhomogeneity. Key physical effects include (i) the influence of the Ampère force on plasma motion, (ii) the influence of the electric dynamo field vortex on the plasma, and (iii) nonlinear Ohm’s law. The model is applicable to the D, E, and F regions of the ionosphere. Simulations indicate that PMHDE in the F-region have lifetimes of several thousand seconds, with initial excitation sizes changing by only ~ 25% over ~ 1500 s. The excitation in the vertical magnetic field component maintains its shape and symmetry within the 250–350 km altitude range. Across seasonal and diurnal variations, the results consistently show stronger magnetic field disturbances during daytime. For an initial excitation amplitude of 90 pT, disturbances reach ~ 30 pT during the day and a few pT at night after ~ 1000 s, with maxima typically occurring in spring and autumn.