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Equatorial Plasma Bubbles (EPBs) are a region of depleted ionospheric densities. EPBs are known to fluctuate both seasonally and day to day, and have been linked to changes in solar activity, geomagnetic activity, and seeding resulting from dynamics occurring at lower altitudes. Here, EPB activity is investigated over a 15-day period with overlapping coincident ground-based 630 nm oxygen airglow measurements, near-infrared hydroxyl mesospheric temperature mapper (MTM) measurements, and Rate Of change of Total Electron Content Index (ROTI) values. The data are compared with the Navy Global Environmental Model (NAVGEM) reanalysis over the same time period. It is found that several days with strong EPB activity coincided with the positive/northward meridional wind phase of the quasi-two-day wave (QTDW) in the mesosphere. These initial observations indicate correlations of the QTDW phase and the occurrence rates of EPBs, and suggest a need for further investigations to assess potential causal relationships that may affect the variability and prevalence of EPBs. 

Abstract Recent evidence has revealed that strong coupling between the lower atmosphere and the thermosphere (100 km) occurs on intra‐seasonal (IS) timescales ( 30–90 days). The Madden‐Julian Oscillation (MJO), a key source of IS variability in tropical convection and circulation, influences the generation and propagation of atmospheric tides and is believed to be a significant driver of thermospheric IS oscillations (ISOs). However, limited satellite observations in the “thermospheric gap” (100–300 km) and challenges faced by numerical models in characterizing this region have hindered a comprehensive understanding of this connection. This study uses an Ionospheric Connection Explorer (ICON)‐adapted version of the Thermosphere Ionosphere Electrodynamics General Circulation Model, incorporating lower boundary tides from Michelson Interferometer for Global High‐resolution Thermospheric Imaging (MIGHTI) observations, to quantify the impact of the upward‐propagating tidal spectrum on thermospheric ISOs and elucidate connections to the MJO. Thermospheric zonal and diurnal mean zonal winds exhibit prominent ( 20 m/s) tidally driven ISOs throughout 2020–2021, largest at low latitudes near 110–150 km altitude. Correlation analyses confirm a robust connection between thermospheric ISOs, tides, and the MJO. Additionally, Hovmöller diagrams show eastward tidal propagation consistent with the MJO and concurrent Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) observations. This study demonstrates that vertically propagating tides play a crucial role in linking IS variability from the lower atmosphere to the thermosphere, with the MJO identified as a primary driver of this whole‐atmosphere teleconnection. Understanding these connections is vital for advancing our knowledge in space physics, particularly regarding the dynamics of the upper atmosphere and ionosphere. 

Abstract This study presents multi‐instrument observations of persistent large‐scale traveling ionosphere/atmospheric disturbances (LSTIDs/LSTADs) observed during moderately increased auroral electrojet activity and a sudden stratospheric warming in the polar winter hemisphere. The Global Ultraviolet Imager (GUVI), Gravity field and steady‐state Ocean Circulation Explorer, Scanning Doppler Imaging Fabry–Perot Interferometers, and the Poker Flat Incoherent Scatter Radar are used to demonstrate the presence of LSTIDs/LSTADs between 19 UT and 5 UT on 18–19 January 2013 over the Alaska region down to lower midlatitudes. This study showcases the first use of GUVI for the study of LSTADs. These novel GUVI observations demonstrate the potential for the GUVI far ultraviolet emissions to be used for global‐scale studies of waves and atmospheric disturbances in the thermosphere, a region lacking in long‐term global measurements. These observations typify changes in the radiance from around 140 to 180 km, opening a new window into the behavior of the thermosphere. 

Abstract A statistical study of 18 years of diurnal temperature tides observed by the SABER instrument on board the TIMED satellite reveals a substantial response of the tides in the upper atmosphere (>60 km) to the Madden‐Julian Oscillation (MJO) in the tropical troposphere. Nonmigrating tidal amplitudes are modulated at the intraseasonal MJO periods up to ~25% relative to the seasonal mean, twice as much as for the migrating tides (~10%). We fully characterize the tidal response for active MJO days as a function of season and MJO location as prescribed by the MJO index. The MJO modulation of the tides was predicted by models but could not be unequivocally observed before. Our results further point to an important role of background winds that partly cause a different response for equatorial and nonequatorial tidal modes in different seasons, which has implications for the MJO imprint on the ionospheric dynamo region. 

Abstract The Madden‐Julian Oscillation (MJO), an eastward‐moving disturbance near the equator (±30°) that typically recurs every ∼30–90 days in tropical winds and clouds, is the dominant mode of intraseasonal variability in tropical convection and circulation and has been extensively studied due to its importance for medium‐range weather forecasting. A previous statistical diagnostic of SABER/TIMED observations and the MJO index showed that the migrating diurnal (DW1) and the important nonmigrating diurnal (DE3) tide modulates on MJO‐timescale in the mesosphere/lower thermosphere (MLT) by about 20%–30%, depending on the MJO phase. In this study, we address the physics of the underlying coupling mechanisms using SABER, MERRA‐2 reanalysis, and SD‐WACCMX. Our emphasis was on the 2008–2010 time period when several strong MJO events occurred. SD‐WACCMX and SABER tides show characteristically similar MJO‐signal in the MLT region. The tides largely respond to the MJO in the tropospheric tidal forcing and less so to the MJO in tropospheric/stratospheric background winds. We further quantify the MJO response in the MLT region in the SD‐WACCMX zonal and meridional momentum forcing by separating the relative contributions of classical (Coriolis force and pressure gradient) and nonclassical forcing (advection and gravity wave drag [GWD]) which transport the MJO‐signal into the upper atmosphere. Interestingly, the tidal MJO‐response is larger in summer due to larger momentum forcing in the MLT region despite the MJO being most active in winter. We find that tidal advection and GWD forcing in MLT can work together or against each other depending on their phase relationship to the MJO‐phases.