The influence of atmospheric tide and planetary wave variability during sudden stratosphere warmings on the low latitude ionosphere

Abstract

[1] Numerical simulations are performed for a sudden stratosphere warming (SSW) under different atmospheric tide and planetary wave forcing conditions to investigate the tidal variability in the mesosphere and lower thermosphere (MLT). The influence of variability of different tides in the MLT on generating perturbations to the low latitude ionosphere is also investigated. Significant changes are found to occur in the migrating semidiurnal solar (SW2) and lunar (M2) tides as well as in the westward propagating nonmigrating semidiurnal tide with zonal wave number 1 (SW1). The changes in the zonal mean atmosphere that occur during SSWs lead to an enhancement in the SW2 and M2 tides. The vertical wavelength of the SW2 is also changed, resulting in phase variability in the SW2 at a constant altitude. Significant enhancements in the SW1 are found to occur only in the presence of additional planetary wave forcing, and this demonstrates that nonlinear planetary wave-tide interactions lead to the enhanced SW1 during SSWs. The amplitude and phase variability of the SW2 is found to be capable of producing temporal variability in the vertical plasma drift velocity that is similar to the observed variability. Changes in the M2 during SSWs can contribute up to an additional 30% of the total ionosphere variability; however, the overall influence of the lunar tide is found to be dependent upon the phase of the moon relative to the timing of the SSW. Although the influence is relatively minor, the SW1 also contributes to the low latitude ionosphere variability during SSWs. The simulation results for the vertical plasma drift velocity and total electron content (TEC) further illustrate that significant longitude variability occurs in the ionosphere response to SSWs.

Quasi-16-day periodic meridional movement of the equatorial ionization anomaly

“…Forbes and Zhang (2012) concluded that changes in the zonal wind in connection with SSW are responsible for the amplification of lunar tide. Pedatella and Liu (2013) investigated importance of planetary wave amplitude and zonal wind for the modification of tides in the MLT region using Whole Atmosphere Community Climate Model (WACCM) simulations, and concluded that changes in the zonal mean atmosphere are the dominant reason for the amplification of the solar and lunar semidiurnal tides. Since the cycle of the lunar age is 29.53 days, the semidiurnal lunar tide has a periodicity of 14.76 days, which is consistent with periodicity observed in our ionospheric data (Figs.…”

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

“…Numerical studies have shown that an amplification occurs in both solar and lunar semidiurnal tides at dynamo-region heights in response to stratospheric sudden warmings (Pedatella et al 2012bPedatella and Liu 2013). Those tidal changes can result from changes in the mean flow (e.g., Stening et al 1997), interaction with planetary waves (e.g., Liu et al 2010;, and changes in the tidal sources (e.g., Goncharenko et al 2012).…”

“…Stening (2011Stening ( ), analyzing equatorial data during 1960Stening ( -2009, also noted that not all stratospheric sudden warmings cause a counter electrojet event. A numerical study by Pedatella and Liu (2013) showed that the lunar tidal amplification depends on the phase of the moon relative to the timing of the stratospheric sudden warming. Thus, the magnitude of the lunar tidal amplification is not solely dependent on the magnitude of the stratospheric sudden warming.…”

Vertical coupling of atmospheres: dependence on strength of sudden stratospheric warming and solar activity

“…If in addition to the increase in temperature the usual wintertime eastward zonal mean zonal wind at 10 hPa and at 60°N reverses its direction, then the event is called major or else minor (Andrews et al 1987). During SSW events, the interaction between enhanced planetary waves and tides and the interaction between tides and modified middle atmosphere modulate the tidal components, which register their signature in the upper atmospheric parameters (Jin et al 2012;Pedatella and Liu 2013;Guharay et al 2014). Also, nonlinear interaction between PWs and tides produces additional waves at the sum and the difference frequencies of the two original waves (Teitelbaum and Vial 1991) which fall mainly in the tidal domain.…”