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The toxin–antitoxin (TA) genetic module controls various bacterial events. Novel toxins with different functions are still being discovered. This study aimed to determine whether the ECs3274-ECs3275 gene pair encoded by enterohemorrhagic Escherichia coli O157 functions as a TA system. To characterize this putative TA system, we analyzed the growth of E. coli expressing ECs3274, ECs3275, or both; the interaction between ECs3274 and ECs3275 using bacterial adenylate cyclase two-hybrid assays; and the DNA-binding ability of ECs3274 using gel-mobility shift assays. We observed that the ECs3274 antitoxin interacted with the ECs3275 toxin, was destabilized by Lon protease, and repressed its promoter activity via its helix-turn-helix (HTH) motif. These properties are consistent with those of typical type II TA antitoxins. Interestingly, ECs3275 has an HTH motif not observed in other TA toxins and is necessary for ECs3275 toxicity, suggesting that ECs3275 may exert its toxicity by regulating the expression of specific genes. [ABSTRACT FROM AUTHOR]

This study explores the meteorological source and vertical propagation of gravity waves (GWs) that drive daytime traveling ionospheric disturbances (TIDs), using the specified dynamics version of the SD-WACCM-X (Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension) and the SAMI3 (Sami3 is Also a Model of the Ionosphere) simulations driven by SD-WACCM-X neutral wind and composition. A cold weather front moved over the northern-central USA (90–100°W, 35–45°N) during the daytime of 20 October 2020, with strong upward airflow. GWs with ~500–700 km horizontal wavelengths propagated southward and northward in the thermosphere over the north-central USA. Also, the perturbations were coherent from the surface to the thermosphere; therefore, the GWs were likely generated by vertical acceleration associated with the cold front over Minnesota and South Dakota. The convectively generated GWs had almost infinite vertical wavelength below ~100 km due to being evanescent. This implies that the GWs tunneled through their evanescent region in the middle atmosphere (where a squared vertical wavenumber is equal to or smaller than 0) and became freely propagating in the thermosphere and ionosphere. Medium-scale TIDs (MSTIDs) also propagated southward with the GWs, suggesting that the convectively generated GWs created MSTIDs.

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. Plain Language Summary: Accompanying the generation of equatorial plasma bubble (EPB), an extra structure with plasma density enhancement may occur. The density‐enhanced structure is known as plasma blob. Generally, plasma blobs mainly appear at the poleward edge of EPB, being low‐latitude phenomena occurring at 10–20° magnetic latitudes. Whereas previous simulations showed that plasma blobs could appear at the east/west side of EPBs, there were few observational evidences and the driving mechanism is unclear. In this study, midlatitude plasma blob‐like structures occurring up to 40°N magnetic latitude was observed along with super EPBs during magnetic storm. Different from most blobs appearing at the EPB poleward edge, the blob‐like structures in the present study appeared at both the EPB poleward and westward edges. By using ground‐based observations from GNSS receiver networks and in‐situ measurements onboard spacecraft, the morphology and evolution of the super plasma blob‐like structures are visualized. Potential mechanisms responsible for their generation are investigated. The results highlight the coexistence of large‐scale plasma depletion and blob structures and their complex evolution with longitude and latitude, and have implications for better understanding the sudden changes of plasma density in time and altitude observed by radar. Key Points: Super plasma blob‐like structures occurred up to 40°N MLat along with equatorial plasma bubbles near sunrise during storm timeThe blob‐like structures mainly occurred at the bubble poleward and westward edges and migrated westward along with the bubbleThe poleward development and evolution of the bubble could contribute to the formation of super blob‐like structures [ABSTRACT FROM AUTHOR]

A Low lAtitude long Range Ionospheric raDar (LARID), which was built recently at Dongfang (19.2°N, 108.8°E, magnetic latitude 13.9°), Hainan Is., China, is employed to study the ionospheric variability over a large region. The LARID consists of two high frequency (HF) coherent backscatter radars, looking toward east and west, respectively, with a field‐of‐view covering a wide longitude from Africa to Pacific. Here we report some results by the LARID, with main focus on its capabilities, advantages and limitations in monitoring ionospheric variability. The results show that the LARID can detect various ionospheric variations at low latitudes, including (a) sequentially generated equatorial plasma bubbles over a longitude span of ∼80°, (b) near‐range E region irregularities drifting across more than 1,000 km, (c) ionospheric background information retrieved from ground scatters, (d) traveling ionospheric disturbances, and (e) sporadic E structures reflecting HF radio waves at low elevation angles. It is demonstrated that the LARID provides an important tool for investigating different types of ionospheric variability over a broad region, especially over the Indian Ocean and west Pacific, and will contribute significantly to the regional ionospheric weather forecasting. Plain Language Summary: The ionosphere is almost always undergoing various variations. At low latitudes, there is a lack of single‐station instrument capable of continuously monitoring ionospheric variability over a large area ranging thousands of kilometers, especially over the oceans where ground‐based observations may suffer from data gaps. For the purpose of monitoring the low latitude ionospheric variability over a broad region, a Low lAtitude long Range Ionospheric raDar (LARID) was built recently at Hainan Is., China, under the support of Chinese Meridian Project phase II. This paper demonstrates how the LARID could perform over‐the‐horizon investigations on different kinds of ionospheric variability. Based on LARID backscatter echoes, equatorial bubbles were observed sequentially after sunset over more than 8,000 km in longitude, and E region irregularities were revealed to drift across more than 1,000 km zonally. Based on the LARID ground scatters with different echo patterns, we succeeded in retrieving the background plasma density, tracing traveling ionospheric disturbances, and characterizing Es layer reflecting high frequency radio waves. Discussions on the capabilities, advantages and limitations of LARID in monitoring the various kinds of low latitude ionospheric variability, and its possible applications in regional ionospheric weather are involved. Key Points: A Low lAtitude long Range Ionospheric raDar (LARID) is employed to investigate ionospheric variability over a large zonal regionLARID shows capabilities in studying ionospheric irregularity, traveling disturbance and background variation over a longitude span of ∼90°Both advantages and limitations of LARID in investigating different types of ionospheric variability, and possible applications are discussed [ABSTRACT FROM AUTHOR]

Using the high-rate phase and amplitude scintillation data from FORMOSA7/COSMIC two mission and back-propagation method, we geolocate plasma irregularities that cause scintillations. The results of geolocation are compared with the NASA GOLD UV image data of plasma bubbles. The root mean square of the zonal difference between estimated locations of plasma irregularities and plasma bubbles are about 1.5° and for single intersection cases 0.5° in the magnetic longitude. The geolocation data provide more accurate scintillation location around the globe compared to assigning to the tangent point and is valuable space weather product, which will be routinely available for public use. [ABSTRACT FROM AUTHOR]

An unseasonal equatorial plasma bubble (EPB) event occurred in the East/Southeast Asian sector during the geomagnetic storm on 1 December 2023, causing strong amplitude scintillations from equatorial to middle latitudes. Based on the observations from multiple instruments over a large latitudinal and longitudinal region, the spatial features of the super EPB were investigated. The EPB developed vertically at a fast rising speed ∼470 m/s over the magnetic equator and extended to a very high middle latitude more than 40°N, despite that the storm intensity was not very strong with the minimum SYM‐H index −132 nT. In the zonal direction, the super EPB covered over a specific region ∼95–140°E, where the local sunset roughly coincided with southward turning of interplanetary magnetic field (IMF) Bz component. Before the onset of the super EPB, significant upward plasma drift up to ∼110 m/s was observed over the magnetic equator, which could amplify the growth rate of Rayleigh‐Taylor instability and lead to the generation of the super EPB. The significant drift was likely caused by eastward penetration electric field (PEF) due to sharp southward turning of IMF Bz. The local time of storm onset and duration of IMF Bz southward turning during the storm main phase may partly determine the onset region and zonal coverage of the EPB. Plain Language Summary: Previous studies have reported unexpected generation and development of equatorial plasma bubbles (EPBs) during geomagnetic storms, with different EPB morphology varied from case to case. It is important to figure out potential factors controlling the occurrence or absence of EPBs over a specific region during geomagnetic storms, their latitudinal and longitudinal development. In this study, super EPB extending to middle latitudes more than 40°N was observed over a limited zonal region ∼95–140°E during the main phase of the 1 December 2023 geomagnetic storm. Significant upward plasma drift was observed before the onset of the EPB, which coincided with sharp southward turning of interplanetary magnetic field (IMF) Bz that could induce remarkable penetration electric field. Based on the combination of multiple kinds of observations over a large region, the potential factors controlling the generation and development of the EPB over latitude and longitude were investigated. It was suggested that the onset time, duration and intensity of IMF Bz southward turning during the main phase of geomagnetic storm play an important role in controlling the EPB spatial features, including the onset region, zonal coverage and latitudinal extension. Key Points: Ionospheric super bubble with fast rising speed occurred during storm time, extended to more than 40°N and caused strong midlatitude scintillationThe super bubble occurred over a confined longitudinal sector ∼95–140°E where the local sunset roughly coincided with interplanetary magnetic field (IMF) Bz southward turningSignificant upward plasma drift due to penetration electric field (PEF) could be responsible for the generation of the super bubbles [ABSTRACT FROM AUTHOR]