Observational evidence of ionospheric migrating tide modification during the 2009 stratospheric sudden warming

Abstract

[1] In this paper, modifications of the ionospheric tidal signatures during the 2009 stratospheric sudden warming (SSW) event are studied by applying atmospheric tidal analysis to ionospheric electron densities observed using radio occultation soundings of FORMOSAT-3/COSMIC. The tidal analysis indicates that the zonal mean and major migrating tidal components (DW1, SW2 and TW3) decrease around the time of the SSW, with 1.5-4 hour time shifts in the daily time of maximum around EIA and middle latitudes. The typical ionospheric SSW signature: a semi-diurnal variation of the ionospheric electron density, featuring an earlier commencement and subsidence of EIA, can be reproduced by differencing the migrating tides before and during the SSW period. Our results also indicate that the migrating tides represent $80% of the ionospheric tidal components at specific longitudes, suggesting that modifications of the migrating tides may be the major driver for producing ionospheric changes observed during SSW events, accounting for greater variability than the nonmigrating tides that have been the focus of previous studies. Citation:

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

“…The modulation of the equatorial plasma fountain has been observed in measurements of the F-region equatorial E × B drift (e.g., Chau et al 2009;Fejer et al 2011). Also, the impact on the equatorial anomaly has been revealed by ground-based and satellite measurements of the F-region plasma density (e.g., Goncharenko et al 2010aGoncharenko et al , 2010bYue et al 2010;Pancheva and Mukhtarov 2011;Lin et al 2012). Figure 48 schematically illustrates the vertical coupling of the atmosphere during stratospheric sudden warmings.…”

A Statistical Comparison of Zonal Mean and Tidal Signatures in FORMOSAT-3/COSMIC and Ground-Based GPS TECs

“…Ionospheric variability resulting from this tidal coupling has been observed in the case of some prominent non-migrating (non-Sun synchronous) tidal components, which are more easily distinguished from structures resulting from the normal quiet-time variation of the ionosphere. Such non-migrating tides include DE3 (the non-migrating diurnal tide with eastward zonal wavenumber 3) Lin et al 2007), and SW1 (the non-migrating semidiurnal tide with westward zonal wavenumber 1) (Pedatella and Forbes 2010;Lin et al 2012).…”

“…Results from such frequency-wavenumber tidal decomposition have found that along with the zonal mean field, the migrating tidal components comprise most of the normal quiet-time variation in the ionosphere, including diurnal plasma uplift from the equatorial fountain to form the equatorial ionization anomalies (EIAs), as well as that resulting from in-situ photoionization (Mukhtarov and Pancheva 2011;Lin et al 2012). In addition to the aforementioned sources, migrating ionospheric tidal components can also reflect changes arising from migrating tides in the middle and lower atmosphere, making the contribution of in-situ ionospheric migrating tidal sources difficult to separate from lower atmospheric sources (Mukhtarov and Pancheva 2011).…”

“…Nonetheless, migrating tidal modulation by nonlinearly-interacting propagating planetary waves has been suggested as a possible medium for transmitting multi-day planetary wave periodicities into the ionosphere (Pancheva et al 2006). Recent observations have also shown that short-term variation in ionospheric fields during stratospheric sudden warmings (SSWs) can be attributed to changes in the amplitudes and phases of the migrating ionospheric tidal components (Fang et al 2012;Lin et al 2012). …”

“…Due to their large amplitudes, changes in the migrating ionospheric tides will have a disproportionate effect on the overall variation of the ionosphere, compared to nonmigrating tides (Lin et al 2012).…”