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The growth and evolution of nocturnal ionospheric plasma irregularities are analyzed over the geomagnetic equatorial station Trivandrum (8.5°N, 77°E, dip latitude 1.9°N) using multi‐instrumental techniques during various seasons of moderate and high solar activity periods. Irregularities are classified into three categories based on their structure and the vertical extent of radar backscattered echoes as Bottom Type, Top Side, and Bottom Type‐Top Side structures. The presence or absence of energy cascading across different scale sizes is identified from the presence of irregularities as Equatorial Spread F (ESF) in digisonde, scintillation in GNSS and backscattered echoes in HF radar with the signals manifesting sequentially or otherwise in these instruments. Threshold values of the duration (2.25 hr) and altitudinal extent (430 km) of ESF irregularities (observed with the digisonde) required for effective energy cascading across scale sizes are identified. The bottom type irregularity layers are observed to form in the equatorial region, Trivandrum, when the post‐sunset F region height varied within the range of 280–370 km which is broader in comparison to those observed at low latitudes. An empirical model is developed using post‐sunset ionospheric height to predict the maximum altitudinal extent of ESF irregularities. This serves as an indicator of the energy cascading process across scale sizes. The altitudinal extent of irregularities predicted by the empirical model also serves as a proxy for the occurrence of plasma bubbles, which has significant adverse implications for communication and navigation systems.

This research is a development work on the total edge irregularity strength of series-parallel graphs. The total edge irregularity strength of series composition of isomorphic uniform theta graphs has been determined. But the total edge irregularity strength of uniform theta graphs itself is an open problem. In this paper, we determine the total edge irregularity strength of uniform theta graphs with one variable is fixed. In the end we determine the total edge irregularity strength of uniform theta graphs in general.

The occurrence of plasma irregularities and ionospheric scintillation over the Caribbean region have been reported in previous studies, but a better understanding of the source and conditions leading to these events is still needed. In December 2021, three ground-based ionospheric scintillation and Total Electron Content monitors were installed at different locations over Puerto Rico to better understand the occurrence of ionospheric irregularities in the region and to quantify their impact on transionospheric signals. Here, the findings for an event that occurred on March 13–14, 2022 are reported. The measurements made by the ground-based instrumentation indicated that ionospheric irregularities and scintillation originated at low latitudes and propagated, subsequently, to mid-latitudes. Imaging of the ionospheric F-region over a wide range of latitudes provided by the GOLD mission confirmed, unequivocally, that the observed irregularities and the scintillation were indeed caused by extreme equatorial plasma bubbles, that is, bubbles that reach abnormally high apex heights. The joint ground- and space-based observations show that plasma bubbles reached apex heights exceeding 2600 km and magnetic dip latitudes beyond 28°. In addition to the identification of extreme plasma bubbles as the source of the ionospheric perturbations over low-to-mid latitudes, GOLD observations also provided experimental evidence of the background ionospheric conditions leading to the abnormally high rise of the plasma bubbles and to severe L-band scintillation. These conditions are in good agreement with the theoretical hypothesis previously proposed.

Monitoring the generation and movement of equatorial plasma bubbles (EPBs) in a large longitude region is crucial important for better understanding their day‐to‐day variability. Using the newly developed Low lAtitude long Range Ionospheric raDar (LARID) at Dongfang (19.2°N, 108.8°E, dip lat. 13.8°N), China, an extremely long‐range experiment for observing EPB irregularities in a range of ±9,600 km to the radar site was first carried out. The results show that EPB irregularities with ranges up to 7,000 and 9,500 km were observed by the east and west beams of LARID, respectively. By incorporating simultaneous observations from GNSS receiver and ionosonde networks, it is demonstrated that the EPBs generated from post‐sunset to sunrise over a very wide longitude of ∼140°, from Pacific to Africa could be observed by LARID. The results, for the first time, demonstrate the possibility for tracing global EPBs in real time using a few low latitude over‐the‐horizon radars. Plain Language Summary Equatorial plasma bubble (EPB), which can cause severe ionospheric scintillation, is an important space weather phenomenon. The occurrence of EPBs exhibits complex longitude variation characteristics. Due to the fact that most of the equatorial and low latitude region is covered by ocean, it is challenging to monitor the generation and movement of global EPBs. Recently, an over‐the‐horizon (OTH) radar at low latitude, that is, the LARID, has been built for observing EPB irregularities. However, it is not clear that how far an OTH radar at low latitude can observe irregularities. This would be very important in the design of a low latitude OTH radar network for tracing global EPB irregularities. To address this issue, an extremely long‐range experiment covering a wide longitude of about 180° was performed for the first time with LARID. The successful observation of EPB irregularities from Pacific to Africa sectors demonstrates the possibility of monitoring the complex longitudinal variations of EPBs by an OTH radar, even during geomagnetic storms. The results provide meaningful insight for building a low latitude OTH radar network in future, that consists of three to four OTH radars could have the capability to obtain global EPBs in real time. Key Points First extremely long‐range experiment for observing equatorial plasma bubbles over a large longitude was conducted Equatorial plasma bubbles with ranges as far as 9,500 km were successfully observed by an over‐the‐horizon radar The results demonstrate the capability for tracing global equatorial plasma bubbles using a few low latitude over‐the‐horizon radars

We present new insights into post-sunrise ionospheric irregularities in Southeast Asia during the intense geomagnetic storm of 19–20 April 2024. By utilizing Total Electron Content (TEC) and Rate of TEC Change Index (ROTI) maps, along with ionosondes, we identified the emergence of post-sunset Equatorial Plasma Bubbles (EPBs)—plasma depletion structures and irregularities—in western Southeast Asia on 19 April. These EPBs moved eastward, and the irregularities dissipated before midnight after the EPBs covered approximately 10° of longitude. Interestingly, plasma density depletion structures persisted and turned westward after midnight until post-sunrise the following day. Concurrently, an increase in F-region height from midnight to sunrise, possibly induced by the storm’s electric field, facilitated the regeneration of irregularities in the residual plasma depletions during the post-sunrise period. The significant increase in F-region height was particularly pronounced in western Southeast Asia. As a result, post-sunrise irregularities expanded their latitudinal structure while propagating westward. These findings suggest that areas with decayed plasma depletion structures from post-sunset EPBs that last past midnight could be sites for creating post-sunrise irregularities during geomagnetic storms. The storm-induced electric fields produce EPBs and ionospheric irregularities at longitudes where the surviving plasma depletion structures of post-sunset EPBs are present.

High‐altitude optical meteors initiating above 150 km are exceedingly rare, with confirmed observations largely confined to the Leonids. Using the Meteor and ionospheric Irregularity Observation System, we recorded a bright 43‐Cassiopeiids fireball with heterogeneous material. It initiated luminously at an exceptional altitude of 157.8 ±$\\pm $0.34 km and began ablating at ∼112.0 km. Multiple flares between 101.6 and 79.5 km were accompanied by a ∼160 s non‐field‐aligned plasma irregularity (NFAI), directly linking irregularity formation to meteoroid fragmentation. The >4 s delay between the optical event and the radar NFAI echo indicates that dust‐driven NFAIs can develop on a timescale of seconds, as ablated material vapor re‐condenses, charges, and organizes into Bragg‐scale structures. This observation provides the first direct evidence for second‐scale NFAI formation by meteors, and offers new constraints on meteor dust‐driven plasma irregularity processes in the mesosphere.

There are two main interrelated goals of this paper. Firstly we investigate the sums

Graph theory has emerged as an influential tool for communication network design and analysis, especially for designing hybrid network topologies for local area networks (LANs). LAN topologies often face challenges related to scalability, data traffic optimization, and security. Designing reliable and efficient hybrid LAN structures remains a critical problem in communication networks. This paper addresses the issue by proposing the application of graph labeling techniques, particularly H-irregularity strength, as a mathematical framework to model and optimize hybrid network topologies. The results illustrate the way theoretical graph labeling and practical network technology interact, offering a novel solution to LAN design problems. This study adds to the expanding field of graph theory applications in communication networks by relating graph theoretical ideas to actual network topologies. With an emphasis on the irregularity strength of particular graph families, the role of graph labeling in optimizing these topologies is explored in this study. The labeling methods that are given offer valuable insights into improving communication efficiency, guaranteeing LAN scalability, and optimizing network architecture. The theoretical underpinnings of the application of graph theory to communication network modelling are strengthened by these discoveries. Labeling methods are introduced in this study to capture topological irregularities and labeling constraints through the use of specialized graphs, such as the Dutch Windmill and Corona product graphs as they both have special labeling characteristics that can be used to improve network performance. In order to secure data and prevent network failures, a three-unit organization structure with a shared administrator is used in network design and optimization. A model of hybrid ring topology of a local area network is considered in this paper and different models are presented which are originated from Dutch Windmill and corona product of graphs. The contribution of this paper is it includes results about a special version of irregularity strength in which the subgraphs used are Dutch windmill graphs and cycle graphs. The edge, vertex and total H -irregularity strength of Dutch Windmill graph and Corona product graph are calculated, offering fresh perspectives on the way they could represent hybrid LAN topologies. The irregularity strength metric is particularly useful even though it measures the imbalance in vertex degrees, which is essential for optimizing communication flow and load balancing within a network. Our theoretical findings illustrate how these labeling schemes can model network behavior, improve resource allocation, and trace data flow effectively. Although the study is primarily theoretical, it offers groundwork for practical network simulation and real-world implementation. Future work will focus on validating the models through simulations and assessing performance metrics such as latency, throughput, and fault recovery. A key limitation of the current study is the absence of empirical performance validation, which is identified as an important direction for further research.

Machine learning offers empirical methods to sift through accounting datasets with a large number of variables and limited a priori knowledge about functional forms. In this study, we show that these methods help detect and interpret patterns present in ongoing accounting misstatements. We use a wide set of variables from accounting, capital markets, governance, and auditing datasets to detect material misstatements. A primary insight of our analysis is that accounting variables, while they do not detect misstatements well on their own, become important with suitable interactions with audit and market variables. We also analyze differences between misstatements and irregularities, compare algorithms, examine one-year- and two-year-ahead predictions and interpret groups at greater risk of misstatements.

Previous theoretical simulations showed the generation of double‐layer structures of E‐region field‐aligned irregularities (FAIs). In this study, we report the double‐layer structures of E‐region FAIs observed by an all‐sky radar at low latitude Ledong (18.4°N, 109°E), China. These FAIs appeared at the altitudes ∼90 and 110 km respectively. Both layers displayed quasi‐periodic patterns with synchronized spatial features, that is, being manifested as spatially separated patches or wavelike structures over similar longitudes at the two layers simultaneously. The neutral wind observations revealed the existence of wind shears at two separated altitudes where the double FAI layers occurred. The two wind shears created two vertically separated sporadic E layers and possibly drove the generation of the double‐layer FAIs via gradient drift instability. The synchronized spatial features of the FAIs at the two layers could be modulated by gravity waves. Plain Language Summary The E‐region field‐aligned irregularities (FAIs) were observed usually in a form of single layer. Due to the limited field of view of narrow‐beam radars which were traditionally employed for observing ionospheric irregularity, the spatial morphology and evolution of E‐region FAIs in a small region were resolved. Owing to the recently developed capability of all‐sky radars in observing E‐region irregularities, the spatial features of E‐region irregularities over a larger zonal region up to hundreds of kilometers in the horizontal plane can be derived. Further, the spatial features of E‐region irregularities in the vertical direction can be unambiguously determined. Utilizing an all‐sky radar at low latitude Ledong, China, a case of double‐layer structures of E‐region FAIs, which occurred at ∼90 and 110 km altitudes respectively, was observed. The double layers of FAIs spanned a zonal coverage ∼250 km, showing as synchronized spatially separated quasi‐periodic patches or wavelike structures in two layers. Especially, the wavelike structures synchronized in the two layers could provide solid evidence for the crucial role of gravity waves in modulating E‐region irregularities. In combination with the collocated ionosonde Es and neutral wind observations, the physical mechanisms responsible for the generation of the double‐layer E‐region FAIs were discussed. Key Points Double layer structures of E‐region field‐aligned irregularity (FAI) were observed at low latitude by an all‐sky radar Both layers of FAIs were quasi‐periodic type and synchronously manifested as spatially separated patches or wavelike structures The double‐layer FAIs were likely generated by wind shear driven gradient drift instability and modulated by gravity waves