Ionosphere-thermosphere coupling via global-scale waves: new insights from two-years of concurrent in situ and remotely-sensed satellite observations

Abstract

Growing evidence indicates that a selected group of global-scale waves from the lower atmosphere constitute a significant source of ionosphere-thermosphere (IT, 100–600 km) variability. Due to the geometry of the magnetic field lines, this IT coupling occurs mainly at low latitudes (< 30°) and is driven by waves originating in the tropical troposphere such as the diurnal eastward propagating tide with zonal wave number s = −3 (DE3) and the quasi-3-day ultra-fast Kelvin wave with s = −1 (UFKW1). In this work, over 2 years of simultaneous in situ ion densities from Ion Velocity Meters (IVMs) onboard the Ionospheric Connection Explorer (ICON) near 590 km and the Scintillation Observations and Response of the Ionosphere to Electrodynamics (SORTIE) CubeSat near 420 km, along with remotely-sensed lower (ca. 105 km) and middle (ca. 220 km) thermospheric horizontal winds from ICON’s Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) are employed to demonstrate a rich spectrum of waves coupling these IT regions. Strong DE3 and UFKW1 topside ionospheric variations are traced to lower thermospheric zonal winds, while large diurnal s = 2 (DW2) and zonally symmetric (D0) variations are traced to middle thermospheric winds generated in situ. Analyses of diurnal tides from the Climatological Tidal Model of the Thermosphere (CTMT) reveal general agreement near 105 km, with larger discrepancies near 220 km due to in situ tidal generation not captured by CTMT. This study highlights the utility of simultaneous satellite measurements for studies of IT coupling via global-scale waves.

Large‐Scale Wave‐Driven Interactions and Plasma‐Neutral Coupling in the Low‐Latitude Ionosphere‐Thermosphere

“…Previous studies (e.g., Chang et al, 2011;Forbes & Roble, 1990;Forbes et al, 2021;Gasperini et al, 2015Gasperini et al, , 2021Gasperini et al, , 2023Gu et Oberheide et al, 2015;Yiğit et al, 2016) demonstrated that upward propagating waves of tropospheric origin can have remarkable influences on interaction and coupling between large-scale wave structures in the low-latitude IT system. CTMT density (Oberheide et al, 2009) and temperature (Forbes et al, 2014) tides have already been extensively tested and validated with Challenging Minisatellite Payload (CHAMP) satellite data.…”

“…The aggregate effect of these tidal wave components likely forms the antisymmetric structure of WN1 (Figure 8) which can also be seen in the WN1 structures of electron density in DMSP‐18 (Figure 4) and the neutral density in Swarm‐C (Figure 5) data. DW2 and D0 have upper thermospheric sources and are generated in situ by a nonlinear interaction of DW1/SPW1 type (Oberheide et al., 2011a) whereas DW1 has a strong dependency on solar activity and season/latitude (Gasperini et al., 2023). SE2 can propagate from the troposphere.…”

“…The longitudinal ionospheric variability can produce significant D0 and DW2 tidal components through ion drag interactions involving the DW1 excited in situ in the thermosphere during solar activity conditions (Jones et al., 2013). CTMT has been successful in interpretating the Michelson Interferometer for Global High‐resolution Thermospheric Imaging (MIGHTI) instrument on the Ionospheric CONnections (ICON)‐derived zonal and meridional wind diurnal/semidiurnal tidal amplitudes for viscous dissipation and vertical coupling during solar low conditions (Forbes et al., 2022; Gasperini et al., 2023), but without in situ sources of excitation due to tide‐tide or tide‐ion drag nonlinear interactions. Even though the lower thermospheric tidal amplitudes are often larger in ICON/MIGHTI than CTMT, their structures and seasonal variations are in good agreement (Yamazaki et al., 2023).…”

“…Even though the lower thermospheric tidal amplitudes are often larger in ICON/MIGHTI than CTMT, their structures and seasonal variations are in good agreement (Yamazaki et al, 2023). CTMT tidal components have been used and compared to many observational studies, in particular satellite observations (e.g., Forbes et al, 2012Forbes et al, , 2014Forbes et al, , 2022Gasperini et al, 2023;Lieberman et al, 2013;Molina & Scherliess, 2023). Along the same vein, we use contribution of 14 diurnal and semidiurnal components obtained from CTMT to examine the role and contribution of terrestrial sources and forcing from bottom for the scenario of amplitudes of wave number structures of densities derived from Swarm-C and DMSP-F18 data in the low-latitude IT regions for days with geomagnetic activity index Kp below or equal to 3 (K p ≤ 3).…”

“…Non‐linear interactions in the neutral atmosphere with planetary waves generate child waves capable of modulating amplitude of original or parent tidal waves (Chang et al., 2013; Yue et al., 2013). The upward propagating waves present in the tropical troposphere, mesosphere/lower thermosphere (MLT) can impact upper atmospheric temperature, wind, and composition structures (Gasperini et al., 2023; Krier et al., 2021). Vertically propagating tides have profound influences on the transport of energy and momentum from their sources into the MLT region (80–120 km altitude ranges) and beyond until they dissipate and deposit energy and momentum into the background IT (Jones et al., 2014; Liu et al., 2021).…”