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Abstract The May 2024 super storm is one of the strongest geomagnetic storms during the past 20 years. One of the most remarkable ionospheric responses to this event over East and Southeast Asia is the complex ionospheric fluctuations following the storm commencement. The fluctuations created multiple oscillations of total electron content (TEC) embedded in the diurnal variation, with amplitudes up to 10 TECu. Along the same latitude, the fluctuations were nearly synchronized over a wide longitude span up to 35°. In the meridional direction, the fluctuations over low latitudes were the most significant and complex, which contained two main components, the poleward extending oscillations originated from the magnetic equator, and the equatorward propagating traveling ionospheric disturbances (TIDs) from high latitudes. The TIDs likely occurred around the globe. The storm‐time interplanetary electric fields penetrating into equatorial latitudes of the ionosphere and the auroral energy input were suggested to drive the poleward extending oscillations and the equatorward TIDs, respectively. 

Abstract Plasma blob is generally a low‐latitude phenomenon occurring at the poleward edge of equatorial plasma bubble (EPB) during post‐sunset periods. Here we report a case of midlatitude ionospheric plasma blob‐like structures occurring along with super EPBs over East Asia around sunrise during the May 2024 great geomagnetic storm. Interestingly, the blob‐like structures appeared at both the poleward and westward edges of EPBs, reached up to 40°N magnetic latitudes, and migrated westward several thousand kilometers together with the bubble. The total electron content (TEC) inside the blob‐like structures was enhanced by ∼50 TEC units relative to the ambient ionosphere. The blob‐like structure at the EPB poleward edge could be partly linked with field‐aligned plasma accumulation due to poleward development of bubble. For the blob‐like structure at the EPB west side, one possible mechanism is that it was formed and enhanced accompanying the bubble evolution and westward drift. 

Abstract Based on the meteor winds measured at Mohe (MH; 53.5°N, 122.3°E) and the reanalysis data, we investigate the variations of planetary waves in the mesosphere and lower thermosphere (MLT) region during the 2019/2020 Arctic winter. Four stratospheric polar warmings, including two sudden stratospheric warmings (SSWs), are observed from November 2019 to March 2020. Quasi‐10‐day waves (Q10DWs) are found to be enhanced following three of these warmings in the zonal winds in the MLT region over MH, but unusually weak after the SSW in February 2020. The trigger mechanisms of the enhanced Q10DWs are investigated and the reason for the unusually weak Q10DWs in February is revealed. Upward propagations and in situ generations of Q10DWs are both limited during the February SSW. Our analysis indicates that Q10DWs in the MLT region in February 2020 are largely inhibited by the extremely strong polar vortex and a lack of mesospheric instability. 

Abstract Mesospheric winds from three longitudinal sectors at 65°N and 54°N latitude are combined to diagnose the zonal wave numbers (m) of spectral wave signatures during the Southern Hemisphere sudden stratospheric warming (SSW) 2019. Diagnosed are quasi‐10‐ and 6‐day planetary waves (Q10DW and Q6DW,m = 1), solar semidiurnal tides withm = 1, 2, 3 (SW1, SW2, and SW3), lunar semidiurnal tide, and the upper and lower sidebands (USB and LSB,m = 1 and 3) of Q10DW‐SW2 nonlinear interactions. We further present 7‐year composite analyses to distinguish SSW effects from climatological features. Before (after) the SSW onset, LSB (USB) enhances, accompanied by the enhancing (fading) Q10DW, and a weakening of climatological SW2 maximum. These behaviors are explained in terms of Manley‐Rowe relation, that is, the energy goes first from SW2 to Q10DW and LSB, and then from SW2 and Q10DW to USB. Our results illustrate that the interactions can explain most wind variabilities associated with the SSW. 

Abstract A quasi‐27‐day wave (Q27DW) caused by the rotational period of solar radiation is commonly observed in the atmospheric dynamics. In the present study, we report an enhancement of a Q27DW during recurrent geomagnetic storms in the autumn of 2018 based on the zonal wind observations in the mesosphere and lower thermosphere (MLT) region over Beijing (BJ, 40.3°N, 116.2°E). According to our analysis, the solar radiation and the seasonal variation are not important in exciting the observed Q27DW. A 27‐day oscillation exists in both solar wind data andKpindex during the recurrent geomagnetic storms. The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperature and ozone data also reveal a Q27DW signature at 97 km. Using the long‐term observation of BJ meteor radar, two more cases are found during springtime in 2010 and 2018 under the solar quiet condition. Our results indicate that the recurrent geomagnetic storms due to high‐speed solar winds can modulate the temperature and ozone in the MLT region, which is responsible for generating a Q27DW in the MLT zonal winds over BJ. This study suggests that the variation of planetary waves in the MLT neutral winds at mid‐latitude is likely associated with the recurrent geomagnetic storms and high‐speed solar winds.