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Abstract Mesopause‐region (87 km) gravity waves (GWs) generated by tropical convection are investigated within the four longitude sectors encompassing Africa, the Indian Ocean, the Intertropical Convergence Zone, and South America during the Dec 2023–Feb 2024 Southern Hemisphere monsoon season. Variances () in the OH Q‐line emission measured by the Atmospheric Waves Experiment (AWE) capture GW activity, and precipitation rates (PR) from the Global Precipitation Measurement (GPM) Mission identify regions of convective activity. The zonal component of GWs comprising the between 10S‐10N primarily propagate eastward. The distributions are latitudinally shifted and more confined in local solar time (LST) compared with those of PR. Mesospheric winds (including tides) appear to induce the latitude‐longitude‐LST variability seen in through critical‐level filtering and Doppler‐shifting of the GWs. These new insights into the variability of the GW spectrum entering the ionosphere‐thermosphere system further our understanding of the dynamical connections between tropospheric and space weather. 

Abstract The National Aeronautics and Space Administration (NASA) Atmospheric Waves Experiment (AWE) instrument, launched in November 2023, provides direct observation of small‐scale (30–300 km) gravity waves (GWs) in the mesosphere on a global scale. This work examined changes in GW activity observed by AWE during two major Sudden Stratospheric Warmings (SSWs) in the 2023 and 2024 winter season. Northern Hemisphere (NH) midlatitude GW activity during these events shared similarities. Variations in mesospheric GW activity showed an evident correlation with the magnitude of zonal wind in the upper stratosphere. NH midlatitude GW activity at 87 km was reduced following the onset of SSWs, likely caused by wind filtering and wave saturation. The upward propagation of GWs was suppressed when the zonal wind reversed from eastward to westward in the upper stratosphere. In regions where the zonal wind weakened but remained eastward, the weakened GWs could be due to their refraction to shorter vertical wavelengths. 

As part of an effort to observe and study ionospheric disturbances and their effects on radio signals used by Global Navigation Satellite Systems (GNSS), alternative low-cost GNSS-based ionospheric scintillation and total electron content (TEC) monitors have been deployed over the American sector. During an inspection of the observations made on 28 August 2022, we found increases in the amplitude scintillation index (S₄) reported by the monitors for the period between approximately 17:45 UT and 18:20 UT. The distributed, dual-frequency observations made by the sensors allowed us to determine that the increases in S₄were not caused by ionospheric irregularities. Instead, they resulted from Carrier-to-Noise (C/No) variations caused by a solar radio burst (SRB) event that followed the occurrence of two M-class X-ray solar flares and a Halo coronal mass ejection. The measurements also allowed us to quantify the impact of the SRB on GNSS signals. The observations show that the SRB caused maximum C/No fadings of about 8 dB-Hz (12 dB-Hz) on L1 ~ 1.6 GHz (L2 ~ 1.2 GHz) for signals observed by the monitor in Dallas for which the solar zenith angle was minimum (~24.4°) during the SRB. Calculations using observations made by the distributed monitors also show excellent agreement for estimates of the maximum (vertical equivalent) C/No fadings in both L1 and L2. The calculations show maximum fadings of 9 dB-Hz for L1 and of 13 dB-Hz for L2. Finally, the results exemplify the usefulness of low-cost monitors for studies beyond those associated with ionospheric irregularities and scintillation.