Simulation of midnight temperature maximum winds and post-midnight equatorial spread-F bubbles

The SAMI3/ESF (Sami3 is also a model of the ionosphere/equatorial spread F) code is used to simulate the growth of equatorial plasma bubbles in the presence on a background wind field based on observed winds. The observed winds[1] exhibit the well-known "midnight temperature maximum" (MTM) pattern, shifting from equatorward to poleward after the maximum temperature occurs. The circumstance where the MTM winds are symmetric across the equator is considered; here the meridional wind component in the southern hemisphere is the reverse of the (observed) northern meridional wind. In particular, a converging meridional wind is known to be destabilizing[1]. The timing of the wind pattern relative to the occurence of a seed for the ESF instability is considered. The application of regional-scale wind measurements to the prediction signal-disrupting ionospheric "bubbles" is demonstrated. It is found that the simultaneous occurence of a seed wave and a maximum in the converging meridional wind pattern can produce post-midnight ESF.

[1] Mesquita, R.L.A., et al. (2018), New results on the mid-latitude midnight temperature maximum, Ann. Geophys., 36, 541--553, doi:10.5194/angeo-36-541-2018

[2] Huba, J.D., and J. Krall (2013), Impact of meridional winds on equatorial spread F: Revisited, Geophys. Res. Lett., 40, 1268--1272, doi:10.1002/GRL.50292

Research supported by NRL base funds and NASA.