Search

In 2024, the Chinese Meridian Project (CMP) completed its construction, deploying 282 instruments across 31 stations. This achievement not only provides a robust foundation but also serves as a reference template for the International Meridian Circle Program (IMCP). The IMCP aims to integrate and establish a comprehensive network of ground-based monitoring stations designed to track the propagation of space weather events from the Sun to Earth. Additionally, it monitors various disturbances generated within the Earth system that impact geospace. Over the past two years, significant progress has been made on the IMCP. In particular, the second phase of construction for the China-Brazil Joint Laboratory for Space Weather has been completed, and the North Pole and Southeast Asia networks are under active construction. The 2024 IMCP joint observation campaign was successfully conducted. To facilitate these developments, the scientific program committee of IMCP was established, following the success of 2023 IMCP workshop and the space weather school, which was co-hosted with the Asia-Pacific Space Cooperation Organization (APSCO) and sponsored by Chinese Academy of Sciences (CAS) and Scientific Committee on Solar-Terrestrial Physics (SCOSTEP). Preparations are now underway for the 2024 workshop in collaboration with the National Institute for Space Research (INPE) in Brazil.

This paper provides references for the design and control of high-quality green building indoor environments during the transitional season in severe cold area. A residential building in severe cold area was selected as the research subject, where indoor pollutant CO2 concentrations and temperatures were measured at the beginning of the transitional season. The study explored the variations in indoor pollutant temperatures and CO2 concentrations under natural and non-natural ventilation conditions, in conjunction with an analysis of the occupants' activities. The results demonstrated clear relationships between indoor pollutant CO2 concentrations and temperatures under natural ventilation conditions. Based on these findings, recommendations for natural ventilation strategies that consider both indoor CO2 levels and thermal environment are proposed.

As a place where people do physical activity for health, the indoor air quality of fitness center has a significant impact on human health. To systematically understand the current state of indoor air quality in fitness centers, this study reviews recent literature on the indoor environment of fitness centers, analyzes factors that affect air quality, and proposes a series of technical strategies to improve it. The analysis reveals: 1) Significant pollution issues with the indoor air quality in fitness centers; 2) Notable variations in air quality across different functional areas and time periods; 3) Air quality can be improved by adopting appropriate technical measures. This paper recommends that future air quality management strategies should consider factors such as the intensity of physical activity and crowd density to develop ventilation strategies, aiming for targeted air quality management that varies by area and time.

The Hunga–Tonga volcano eruption at 04:14:45 UT on 15 January 2022 produced various waves propagating globally, disturbing the background atmosphere and ionosphere. Coinciding with the arrival of perturbation waves, several equatorial plasma bubbles (EPBs) were consecutively generated at post-sunset hours over the East/Southeast Asian region, with the largest extension to middle latitudes. These EPBs caused intense L-band amplitude scintillations at middle-to-low latitudes, with signal fading depths up to ~16 dB. Considering the very rare occurrence of EPBs during this season in the East/Southeast Asian sector and the significantly modulated background ionosphere, we believe that the perturbation waves launched by the volcano eruption triggered the generation of the unseasonal super EPBs. The ionospheric perturbations linked with the 2022 Tonga volcano eruption propagated coincidently through the East/Southeast Asia longitude sector near sunset, modulated the equatorial F region bottomside plasma density, and acted as the seeding source for the generation of the unseasonal super bubbles. Our results implicate that volcano eruption could indirectly affect the satellite communication links in the region more than ten thousand kilometers away.

Photocatalytic hydrogenation provides an effective alternative way for the synthesis of industrial chemicals to meet the economic and environment expectations. Especially, over the past few years, metal-organic frameworks (MOFs), featured with tunable structure, porosity, and crystallinity, have been significantly developed as many high-performance catalysts in the field of photocatalysis. In this review, the background and development of photocatalytic hydrogenation are systemically summarized. In particular, the comparison between photocatalysis and thermal catalysis, and the fundamental understanding of photohydrogenation, including reaction pathways, reducing species, regulation of selectivity, and critical parameters of light, are proposed. Moreover, this review highlights the advantages of MOFs-based photocatalysts in the area of photohydrogenation. Typical effective strategies for modifying MOFs-based composites to produce their advantages are concluded. The recent progress in the application of various types of MOFs-based photocatalysts for photohydrogenation of unsaturated organic chemicals and carbon dioxide (CO2 ) is summarized and discussed in detail. Finally, a brief conclusion and personal perspective on current challenges and future developments of photocatalytic hydrogenation processes and MOFs-based photocatalysts are also highlighted.

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]

This study investigated the latitudinal variations of post‐sunset enhancements in the ionospheric electron density during the geomagnetic quiet period in May 2021 with a combination of high‐precision ionospheric parameters obtained from four ionosondes, Beidou geostationary satellite (BD‐GEO) receiver network and Sanya incoherent scatter radar (SYISR). We identified four categories of post‐sunset enhancement phenomena (Types 1–4), each with unique spatial and temporal evolutions, yet uniformly accompanied by a decrease in hmF2. Measurements of plasma drift vector velocities from SYISR and hmF2 gradients across various latitudes provided pivotal insights, confirming that the ionospheric post‐sunset enhancements can result from downward plasma motion due to westward electric field, downward field‐aligned drift, or a combination of both. For Type 1, dominated by field‐aligned drift, plasma density enhancements not only intensify at low latitudes but may also extend to mid‐latitudes, exhibiting a distinct temporal delay with increasing latitude. In contrast, Type 4, primarily driven by the westward electric field, is characterized by modest increases in plasma density confined to localized low‐latitude regions, with no observable latitudinal time delay in the peak of enhancements. Types 2 and 3, which are subject to the combined influence of the westward electric field and field‐aligned drift, exhibit plasma density increases at certain low‐latitude areas, with Type 2 presenting a delayed pattern and Type 3 showing none with rising latitude. Meanwhile, neutral winds can partially account for the observed post‐sunset enhancement from low to middle latitudes. These findings offer new insights into the factors influencing ionospheric behavior after sunset. Key Points: Four types of distinctive latitudinal variations of post‐sunset enhancements were identified with multiple data sets during the quiet periodAccompanying the increase in the electron density at sunset, the decrease in hmF2 is favorable for the formation of post‐sunset enhancementDownward field‐aligned drift and westward electric field govern the spatial scale of post‐sunset enhancements at low and middle latitudes [ABSTRACT FROM AUTHOR]

The G‐condition (NmF2 ≤ NmF1) was observed by ground‐based ionosondes at Mohe and Beijing during the geomagnetic storm occurred on 23 and 24 April 2023. We studied exospheric temperature (Tex) responses during the G‐condition. Tex was derived from electron density (Ne) profiles (∼150–200 km) by the method proposed by Li et al. (2023, https://doi.org/10.1029/2022ja030988). The retrieved Tex showed obvious enhancements, with relative deviation of ∼10%–35% and ∼3%–20% at Mohe and Beijing, respectively. Additionally, chemical reaction rate increased by ∼15%–100% and ∼13%–30%, and O/N2 decreased by ∼17%–35% and ∼23%–30% at Mohe and Beijing, respectively. Under photochemical equilibrium assumption, peak Ne is inversely proportional to chemical reaction rate and proportional to O/N2. Increased chemical reaction rate and decreased O/N2 indicate a decrease in peak Ne. Compared to the increased Tex, the relative enhancement in Tex is more significantly associated with the G‐condition, with relative deviation above ∼10% during the G‐condition. Plain Language Summary: Normally, the peak Ne in the F2 layer (NmF2) is the largest in the full Ne profile. G‐conditions are special events in ionospheric observations, when NmF2 is smaller than or equal to NmF1 (i.e., NmF2 ≤ NmF1). Due to shielding effect of the F1 layer, no information above hmF1 can be obtained from ground‐based ionosondes, and Ne peak height is typically below 200 km. In previous works, incoherent scatter radar (ISR) observations are usually used to extract thermospheric parameters (Tex, neutral composition and thermospheric wind). In this paper, ground‐based ionosonde observations (∼150–200 km) at Mohe and Beijing prior to, during and after the G‐condition (from 22 to 26 April 2023) were selected to derive Tex using the method proposed by Li et al. (2023, https://doi.org/10.1029/2022ja030988). Furthermore, corresponding neutral temperature (Tn) and densities were further calculated by replacing the Tex module in the NRLMSISE‐00 model with the retrieved Tex. In our analysis, the retrieved Tex and chemical reaction rate showed significant enhancements and O/N2 showed obvious decrease compared to quiet reference days. This is consistent with the analysis of the mechanism of G‐conditions formation in previous studies. Key Points: The G‐condition (NmF2 ≤ NmF1) was observed by ground‐based ionosondes at Mohe and Beijing during the G4 storm on 24 April 2023Relative enhancements in Tex during the G‐condition were greater than that in other periods, with relative deviation above ∼10%Enhanced Tex with corresponding increased chemical reaction rate and decreased O/N2 collectively contributed to a decrease in Ne [ABSTRACT FROM AUTHOR]

The ionosonde is widely used for detecting electron density profiles below the F2 peak altitude. Extracting precise profiles from ionograms is crucial, as it serves as a significant data source for ionospheric studies and applications. In our study, we utilized the ray tracing profile inversion method (RTPI) to derive more realistic electron density profiles from the ionosonde observations. By comparing the electron density profiles inverted by RTPI method with and without geomagnetic field against the profiles observed by Incoherent Scatter Radar (ISR) plasma lines, we validated the high precision of the RTPI with magnetic field effect method. The results showed that the average height difference and average peak height difference between profiles inverted by RTPI and plasma line observations are less than 10 and 5 km, respectively. Additionally, we quantified the errors associated with the geomagnetic field effect. It would cause an ∼8–10 km overestimation in true height and a ∼10%–15% underestimation in electron density if the geomagnetic field effect is not considered. These errors induced by the magnetic field accumulate with the frequency of the radio waves. Moreover, we conducted a comparative analysis of simulated echo traces using profiles with different E‐layer shapes. It was demonstrated that the key parameters of the bottom structure have a significant impact on ionogram retrieval, while the E‐layer shape has negligible influence on inversion. Furthermore, we analyzed echo traces simulated using ray tracing with and without collision. The collision effect has weak effect on the delay of the radio waves. Key Points: A more realistic electron density profile is derived from ionosonde observations by considering the full dispersion relationA refined ionogram inversion method using numerical ray‐tracing method has been developed to improve the accuracyThe effects of the magnetic field and collision on electron density inversion are evaluated [ABSTRACT FROM AUTHOR]