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Abstract We examined three observations of green emission events (labeled as event A, B and C, respectively) associated with red sprites as captured by amateurs. In all cases, the green emissions were recorded atop of red sprite. Based on the location of causative strokes and background star fields for events A and B, their altitudes are confined between 88 and 100 km, with the maximum brightness at 90.7 and 95.5 km, respectively. Events B and C were lit up for a second time after the recurrence of a sprite element, extending their duration to approximately 1,084 ms and 732.6 ms, much longer than that (about 500 ms) for event A; the intensity of green emissions was also enhanced due to sprite recurrence. It is inferred that the recurrence of sprite elements could affect the ambient condition by further increasing electron density and strengthening the electric field for the ghost production. 

Abstract The extraordinary eruption of the Tonga volcano on 15 January 2022 lofted material to heights exceeding 50 km, marking the highest observed since the satellite era. This eruption caused significant disturbances spanning from the hydrosphere up to the thermosphere. Our recent investigation discovered the dramatic thermospheric responses at satellite altitudes. This study, however, provides physical insights into two main possible processes, secondary gravity waves (GWs) and Lamb waves, which may explain those observed large‐scale thermospheric disturbances. The comparison between the simulations and observations suggests that the MESORAC‐HIAMCM secondary GWs are consistent with GRACE‐FO measured global‐propagation thermospheric density disturbances in timing and amplitude. WACCM‐X simulations suggest that the Lamb wave can reach the thermosphere as a sharp, narrow wave packet, and may contribute about 25% to the total disturbances at 510 km. 

Abstract Prior observational uncertainties have hindered the clear understanding of the link between tropospheric Lamb waves and ionospheric disturbances. In this study, we precisely extracted ionospheric Lamb waves originating from the epicenter of the 15 January 2022 Tonga eruption, propagating upward in a conical structure. This was achieved by using line‐of‐sight observations from the BeiDou geostationary satellites, which eliminated the spatiotemporal ambiguity introduced by the relative motion of Global Positioning System satellites, enabling the clear extraction of the Lamb signal in the ionosphere. The observed L0 mode speed (∼323 m/s) and period (∼30 min) were consistent with those of the tropospheric Lamb wave. It suggested that the ionospheric Lamb wave is likely driven by the surface Lamb wave, leading to a conical wave‐front that extends in altitude. This study highlights the significant role of Lamb waves in transmitting energy from epicenters through Earth's atmosphere and plasma systems. 

Abstract High‐speed video and electric field records of two positive cloud‐to‐ground (+CG) flashes were used to examine the effect of M‐components on needle activity after the return stroke onset. We observed enhancements of needle activity that were associated with the occurrence of M‐components identified by channel luminosity enhancements both at cloud altitudes and near the ground. Full‐fledged M‐components enhance needle activity via injection of negative charge into the bottom of grounded channel and reversing the direction of the radial electric field at the channel core, similar to +CG return strokes. Attempted M‐components, identified by channel luminosity enhancements at the cloud but not near the ground, did not enhance needle activity because of the absence of significant reflection from the ground, which causes electric field reversal at the core.