Nonlinear interaction of the lunar tide M2 and the diurnal variation of electron density in the ionosphere

It was unclear whether these variations are excited by and tides propagating from the surface into the ionosphere or if the variations are due to a nonlinear interaction of the semidiurnal lunar tide with the diurnal variation of ionization ().

A simulation was performed with the NSF National Center for Atmospheric Research thermosphere‐ionosphere‐mesosphere electrodynamics general circulation model (TIME‐GCM). In the stratosphere at the lower boundary of TIME‐GCM, the signal of the atmospheric semidiurnal lunar tide is introduced. The TIME‐GCM simulation of January–February 2009 shows that the electron density variation in the equatorial region contains not only a spectral component of the period but also spectral components of the and periods fulfilling the nonlinear interaction resonance condition for the frequencies of the wave triads ( + = ) and ( − = ).