Whole Atmosphere Model Simulations of Ultrafast Kelvin Wave Effects in the Ionosphere and Thermosphere

Abstract

This paper examines the response of the upper atmosphere to equatorial Kelvin waves with a period of ∼3 days, also known as ultrafast Kelvin waves (UFKWs). The whole atmosphere model Ground‐to‐topside model of Atmosphere and Ionosphere for Aeronomy (GAIA) is used to simulate the UFKW events in the late summer of 2010 and 2011 as well as in the boreal winter of 2012/2013. When the lower layers of the model below 30‐km altitude are constrained with meteorological data, GAIA is able to reproduce salient features of the UFKW in the mesosphere and lower thermosphere as observed by the Aura Microwave Limb Sounder. The model also reproduces ionospheric response, as validated through comparisons with total electron content data from the Gravity field and steady‐state Ocean Circulation Explorer satellite as well as with earlier observations. Model results suggest that the UFKW produces eastward‐propagating ∼3‐day variations with zonal wavenumber 1 in the equatorial zonal electric field and F region plasma density. Model results also suggest that for a ground observer, identifying ionospheric signatures of the UFKW is a challenge because of ∼3‐day variations due to other sources. This issue can be overcome by combining ground‐based measurements from different longitudes. As a demonstration, we analyze ground‐based magnetometer data from equatorial stations during the 2011 event. It is shown that wavelet spectra of the magnetic data at different longitudes are only in partial agreement, with or without a ∼3‐day peak, but a spectrum analysis based on multipoint observations reveals the presence of the UFKW.

Ionospheric Signatures of Secondary Waves From Quasi‐6‐Day Wave and Tide Interactions

“…(2017). This serves as forcing from the lower atmosphere to the upper layers, thus enabling GAIA to reproduce the ionospheric response to meteorological forcing from below (e.g., Pancheva et al., 2012; Yamazaki, Miyoshi, et al., 2020). Simulations were performed for solar minimum conditions that were held constant using a solar activity index F 10.7 value of 68 solar flux unit (SFU; 10 −22 W m −2 Hz −1 ).…”

Atmosphere‐Ionosphere (A‐I) Coupling as Viewed by ICON: Day‐to‐Day Variability Due to Planetary Wave (PW)‐Tide Interactions

“…Modeling studies (e.g., Fang et al., 2009; Hagan et al., 2007; Jin et al., 2008, 2011) solidified our quantitative understanding of these observations. Analogous to A‐I coupling by tides, observational (Abdu et al., 2015; G. Liu et al., 2015; Onohara et al., 2013; Takahashi et al., 2007) and modeling (Chang et al., 2010; Gu et al., 2014; Yamazaki et al., 2020) studies demonstrated that quasi‐3‐days ultra‐fast Kelvin waves (UFKWs) also impart their variability on the ionosphere through the dynamo mechanism.…”

“…Analogous to A-I coupling by tides, observational (Abdu et al, 2015;G. Liu et al, 2015;Onohara et al, 2013;Takahashi et al, 2007) and modeling (Chang et al, 2010;Gu et al, 2014;Yamazaki et al, 2020) studies demonstrated that quasi-3-days ultra-fast Kelvin waves (UFKWs) also impart their variability on the ionosphere through the dynamo mechanism.…”

Evolution of individual equatorial atmospheric Kelvin waves in the stratosphere from FORMOSAT-7/COSMIC-2 temperatures

“…Studies of UFKW described their general characteristics (see Davis et al (2012) and references therein) and showed that UFKW can travel to thermospheric heights and also drive changes further up (Forbes 2000;Takahashi et al 2007;Forbes et al 2009;Chang et al 2010;Chen et al 2018); however, their effects on the IT region are yet to be examined in detail. Modelling studies are indicating significant effects of UFKW on MLT and IT region including day-to-day variability (Triplett et al 2019;Yamazaki et al 2020).…”