Revisiting the Modulations of Ionospheric Solar and Lunar Migrating Tides during the 2009 Stratospheric Sudden Warming by using Global Ionosphere Specification

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Revisiting the Modulations of Ionospheric Solar and Lunar

Migrating Tides during the 2009 Stratospheric Sudden Warming by

using Global Ionosphere Specification

J. T. Lin1,*, C. Y. Lin2, C. H. Lin1,3, N. M. Pedatella4,5, P. K. Rajesh1, T. Matsuo6 and J. Y. Liu3

1_{Department of Earth Science, National Cheng Kung University, Tainan, Taiwan} 2_{Institute of Space Science, National Central University, Chung-Li, Taiwan} 3_{Earth Dynamic System Research Center, National Cheng Kung University, Tainan,}

Taiwan

4_{High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO,}

USA

5COSMIC Program Oﬃce, University Corporation for Atmospheric Research,

Boulder, CO, USA

6_{Ann and H. J. Smead Department of Aerospace Engineering Sciences, University of}

Colorado Boulder, Boulder, CO, USA

In this study, Global Ionosphere Specification (GIS) based on the Gauss-Markov Kalman filter assimilating the TECs observed from ground-based GPS receivers and space-based radio occultation (RO) instrumentations is applied for investigation of ionospheric day-to-day tidal variability during the 2009 stratospheric sudden warming (SSW) period. With the benefit of GIS improving the temporal and spatial resolution of global electron density distribution, we can retrieve the daily solar tidal solution by using least square fitting. We found that the solar semidiurnal migrating tide (SW2) reveals a prominent reduction followed by enhancement after the peak warming, with recurrent phase decreases and increases occurring at the low magnetic latitude on a period of about 15 days. Previously this SW2 oscillation was considered as a potential driver of the SSW-related ionospheric variation, but the oscillation is indeed close to the beating period (15.13 day) between SW2 and lunar semidiurnal (M2) tides,

suggesting that the M2 should be further considered. Our tidal analyses on the daily GIS clearly prove the intensification of M2 only exists during the SSW period. It also

illustrates that the combined impact of amplitudes and phases of the SW2 and M2 on

the semidiurnal variation in the ionosphere. If one considers the SW2 solely, the resulting ionospheric perturbation shows the phase decreases, on the other hand, combined M2 and SW2 show oscillating amplitudes and phase shifts. Our results

indicate that the M2 variability is important to contribute to the equatorial vertical drift