Mesosphere Research Articles

Bridging Model–Data Discrepancies in Mars’ Dayside Ionosphere: Exploring Varying Reaction Rate Coefficients

Measurements of concentrations of neutral and ion species in the upper atmosphere of Mars by the Neutral Gas and Ion Mass Spectrometer (NGIMS) on board the Mars Atmosphere and Volatile EvolutioN mission have served as model input and/or for comparison with model output in numerous earlier studies of the Martian dayside ionosphere. While many models reproduce the altitudinal density profiles of key ion species within a factor of a few, it has proven challenging to achieve a level of agreement within tens of percent for multiple ion species over a wide range of altitudes. We explore means to overcome this issue while keeping with a reduced chemical model and utilizing the assumptions of photochemical equilibrium and that the NGIMS data are devoid of any measurement errors. We entertain, for instance, the idea that the rate coefficient for the charge-transfer reaction between CO2+ and O may vary with altitude as a result of a pressure-controlled internal energy distribution of the CO2+ population.

Unraveling the untwisting process and upward mass transfer of a twisted prominence driven by vortex motion

Solar filaments or prominences are common features in the Sun's atmosphere that contain cool chromospheric material suspended within the hot corona. However, the intricate topology of these structures and the mechanisms driving their instability and upward material transfer are not well understood. Investigating these issues is essential for gaining insight into the fundamental laws that govern solar activity. This study is to analyze a specific twisted prominence observed on February 10, 2021, and to explore its dynamics, including stability, motion, and material transfer. The study also aims to propose a mechanism, based on the K\'arm\'an Vortex Street instability, to explain the destabilization of the prominence. The study utilizes high-resolution H$_ alpha $ observations from the 1-m New Vacuum Solar Telescope and space-borne observations from the Solar Dynamics Observatory. These observations capture the characteristics and behavior of the twisted prominence. We analyzed the data to investigate the equilibrium state, subsequent destabilization, vortex motion, oscillations, resonations, untwisting, and upward mass loading of the prominence. We also detected and measured the speeds of outflows surrounding the prominence. The study reveals that the observed twisted prominence exhibited a stretched and twisted structure at its apex, distinguishing it from familiar cloudy prominences. Following a period of more than 30 hours in equilibrium, the prominence underwent destabilization, leading to a series of dynamic phenomena, such as vortex motion, oscillations, resonations, untwisting, and the upward transfer of mass. Consequently, material from the top of the prominence was carried upward and deposited into the overlying magnetic arcades. Noteworthy, outflows surrounding the prominence were characterized by speeds exceeding 40 km s$^ Based on these findings, we propose, for the first time, a mechanism rooted in the K\'arm\'an Vortex Street instability to explain the destabilization of the prominence. The estimated typical Strouhal Number of 0.23pm 0.06, which is related to vortex shedding, falls within the expected range for the K\'arm\'an Vortex Street effect, as predicted by simulations. These discoveries provide new insights into the dynamics and fundamental topology of solar prominences and reveal a previously unknown mechanism for mass loading into the upper atmosphere.

Influence of the Sun on the night side of the Earth

Solar radiation breaks hydrogen bonds between water molecules, which prevents their self-organization and destroys water clusters. This may be accounted for by the influence of muons which are generated in the upper atmosphere by the solar wind. Muon flux is anisotropic and changes direction depending on the position of the Sun in the sky. For this reason, the rate of hydrolysis of triethyl phosphite in acetonitrile depends on geometric shape of the reaction solution, its position in space and changes during the day. For example, in three 5 mm NMR-tubes directed North-South, East-West and Vertically the distributions of the rates of this reaction are always different in the daytime. At noon, when the Sun is at its zenith, the rates are considerably higher in the horizontal tubes, and at sunrise and sunset when the Sun shines along the East-West line the rate is higher in the vertical tube. One might assume that at night when the Sun irradiates the opposite side of the Earth, this phenomenon should disappear, and the reaction rates should be the same in all directions. However, it turned out that at midnight the distribution of hydrolysis rates in multidirectional NMR-tubes is the same as at noon. This may indicate that on the night side of the Earth the influence of the Sun is inducing the appearance of some radiation vertically from underground. This phenomenon requires detailed study in different places on the Earth.

The Impact of Polar Vortex Strength on the Longitudinal Structure of the Noontime Mid-Latitude Ionosphere and Thermosphere

Ground-based ionospheric, CHAMP/STAR, and GOCE satellite neutral density ρ observations under deep solar minimum conditions were used to find whether there is a dependence of longitudinal variations on polar vortex strength. Ionospheric stations at fixed-dipole geomagnetic Φ ≈ 38° and geographic φ ≈ 40°N latitudes located in ‘near-pole’ and ‘far-from-pole’ longitudinal sectors were used in the analysis. No significant longitudinal NmF2 (electron concentration in the F2-layer maximum) dependence on the polar vortex strength was revealed. Geomagnetic control was shown to be responsible for the observed longitudinal NmF2 variations. Satellite-observed longitudinal variations in neutral density did not show any visible reaction to the polar vortex strength. However, the impact of sudden stratospheric warming (SSW) on the upper atmosphere is strong enough to change the neutral density longitudinal distribution. The impact of SSW shows a global occurrence and ‘works’ within 3–5 days in geographic coordinates in the vicinity of the SSW peak. Atomic oxygen values retrieved under ‘strong’ and ‘weak’ polar vortex strengths confirm the results obtained on longitudinal variations in NmF2 and ρ. In conclusion, no visible effects related to ‘strong’ or ‘weak’ polar vortex strengths have been revealed in either NmF2 or satellite neutral density longitudinal variations. Alternatively, such effects may be very small and therefore cannot be confirmed experimentally.

The Preparation Phase of the 2022 ML 5.7 Offshore Fano (Italy) Earthquake: A Multiparametric–Multilayer Approach

This paper presents an analysis of anomalies detected during the preparatory phase of the 9 November 2022 ML = 5.7 earthquake, occurring approximately 30 km off the coast of the Marche region in the Adriatic Sea (Italy). It was the largest earthquake in Italy in the last 5 years. According to lithosphere–atmosphere–ionosphere coupling (LAIC) models, such earthquake could induce anomalies in various observable variables, from the Earth’s surface to the ionosphere. Therefore, a multiparametric and multilayer approach based on ground and satellite data collected in each geolayer was adopted. This included the revised accelerated moment release method, the identification of anomalies in atmospheric parameters, such as Skin Temperature and Outgoing Longwave Radiation, and ionospheric signals, such as Es and F2 layer parameters from ionosonde measurements, magnetic field from Swarm satellites, and energetic electron precipitations from NOAA satellites. Several anomalies were detected in the days preceding the earthquake, revealing that their cumulative occurrence follows an exponential trend from the ground, progressing towards the upper atmosphere and the ionosphere. This progression of anomalies through different geolayers cannot simply be attributed to chance and is likely associated with the preparation phase of this earthquake, supporting the LAIC approach.

Selecting the best solar EUV proxy for long-term timescale applications

Solar EUV proxies are a solution to the difficulties in obtaining solar EUV time series covering extended periods or during times without measurements available. Despite being very similar at interannual and decadal timescales, proxies are not identical. The upper atmosphere, highly sensitive to this spectral range, can serve as a “witness” of solar EUV variations to help selecting the best proxy. Its choice can be critical depending on the problem we are trying to solve through the proxy implementation and on the nature of the proxies’ non-identical part variation. We analyze the best proxy selection process whose outcome depends on the method and on the physics knowledge we have of the system. This study aims to contribute and highlight certain critical aspects of selection methodologies. A case where this issue becomes critical is upper atmosphere long-term trends’ estimation in order to detect the increasing greenhouse gas effect along the last decades.

Exoplanet Aeronomy: A Case Study of WASP-69 b’s Variable Thermosphere

Aeronomy, the study of Earth’s upper atmosphere and its interaction with the local space environment, has long traced changes in the thermospheres of Earth and other solar system planets to solar variability in the X-ray and extreme-ultraviolet (collectively, XUV) bands. Extending comparative aeronomy to the short-period extrasolar planets may illuminate whether stellar XUV irradiation powers atmospheric outflows that change planetary radii on astronomical timescales. In recent years, near-IR transit spectroscopy of metastable Hei has been a prolific tracer of high-altitude planetary gas. We present a case study of exoplanet aeronomy using metastable Hei transit observations from Palomar Observatory's Wide Field InfraRed Camera and follow-up high-energy data from the Neil Gehrels Swift Observatory that were taken within 1 month of the WASP-69 system, a K-type main-sequence star with a well-studied hot Jupiter companion. Supplemented by archival data, we find that WASP-69's X-ray flux in 2023 was less than 50% of what was recorded in 2016 and that the metastable Hei absorption from WASP-69 b was lower in 2023 versus past epochs from 2017 to 2019. Via atmospheric modeling, we show that this time-variable metastable Hei signal is in the expected direction given the observed change in stellar XUV, possibly stemming from WASP-69's magnetic activity cycle. Our results underscore the ability of multiepoch, multiwavelength observations to paint a cohesive picture of the interaction between an exoplanet’s atmosphere and its host star.

Accretion of Meteoric Organic Matter at the Surface of Mars and Potential Production of Methane by Ultraviolet Radiation

In this study, a comprehensive model of the meteoric organic cycle on Mars for the current geological period is developed, which characterizes the ablation of exogenous organic matter in the upper atmosphere, the accretion of intact carbon at the surface, and the potential production of methane by UV photolysis from the surface reservoir. The model accounts for both the latitudinal and seasonal variation of the meteoroids’ input from the most relevant populations in the inner solar system. A recent version of the University of Leeds Chemical Ablation Model, which includes a semiempirical model to describe the pyrolysis kinetics of the meteoric organic matter, is then combined with this meteoroid input function and a semiempirical model that quantifies the UV production of methane. The minimum and maximum accretion rates of organics are between 18 and 90 kg sol−1 at aphelion and 45–134 kg sol−1 at the first crossing of the ecliptic plane. The resulting mixing ratios of carbon, in the top 200 μm of the surface layer, range from 0.09–0.43 ppm at 20°N to 4.8–8.9 ppm around the south pole. To be consistent with the methane upper limit of 0.02 ppbv measured by the NOMAD instrument on the ExoMars Trace Gas Orbiter, the UV photolysis yields for methane production need to be around 3% assuming a meteoric carbon content in comets of 25.6 wt% and an atmospheric lifetime of methane of 329 Earth yr. Alternatively, a laboratory estimate of 20% for the methane production yield would require a lifetime of 60 Earth yr.

Differential elastic scattering and electron-impact ionization cross sections of nitrous oxide

With the aim of providing datasets for simulations of electron transport processes in the upper atmosphere, we measured singly differential elastic electron scattering and doubly differential electron-impact ionization cross sections of nitrous oxide. These measurements were conducted for primary electron energies between 30 eV and 1 keV in the angular range of 20°–150°. Secondary electron energies spanned from 4 eV to approximately half of the primary electron energy. In addition to the measurements, the differential elastic scattering cross sections of nitrous oxide were calculated using the IAM-SCAR + I model. Furthermore, the singly differential and total ionization cross sections of nitrous oxide were obtained by integrating the doubly differential ionization cross sections over emission angle and over both emission angle and secondary electron energy, respectively. These cross sections were compared to calculations performed using the BEB model and to experimental results of other groups, who determined the total ionization cross sections of nitrous oxide by collecting ions generated during electron impact.Graphical abstract

China's Ground‐Based Space Environment Monitoring Network—Chinese Meridian Project (CMP)

AbstractMonitoring and investigation of the solar‐terrestrial space environment is a huge challenge for humans in space age. To this end, China has established the Ground‐based Space Environment Monitoring Network, namely Chinese Meridian Project (CMP). The project comprises three major systems: the Space Environment Monitoring System, Data and Communication System, and Scientific Application System. The Space Environment Monitoring System adopts a well‐designed monitoring architecture, known as “One Chain, Three Networks, and Four Focuses,” to achieve stereoscopic and comprehensive monitoring of the entire solar‐terrestrial space. The “One‐Chain” component utilizes optical, radio, interplanetary scintillation, cosmic ray instruments to cover the causal chain of space weather disturbances from the solar surface to near‐Earth space. For the ionosphere, middle and upper atmosphere, and magnetic field, instruments are deployed along longitudes of 120° and 100°E, and latitudes of 30° and 40°N, forming the “Three Networks.” Furthermore, more powerful monitoring facilities or large‐scale instruments have been deployed in four key regions: the high‐latitude polar region, mid‐latitude region in northern China, low‐latitude region at Hainan Island, and the Tibet region. These four regions are crucial for disturbances propagation and evolution, or possess unique geographical and topographical characteristics. The Data and Communication System and Scientific Application System are designed for data collecting, processing, storage, mining, and providing user service based on data acquired by the Space Environment Monitoring System. The data obtained by CMP will be shared with the global scientific community, facilitating enhanced collaboration on space weather and space physics research.

OI 630.0 nm Post‐Sunset Emission Enhancement as an Effect of Tidal Activity Over Low‐Latitudes

AbstractThe OI 630.0 nm airglow emission variability provides salient information on the dynamical changes taking place in the upper atmosphere at around 250 km. The emission rates vary with the changes in the ambient electron densities and the neutral constituents that are associated with these emissions. On several occasions, enhancements in these emissions are observed during post‐sunset hours, around 21 local time (LT), as measured from Mt. Abu (24.6°N, 72.7°E, 19°N Mag), a low‐latitude location at Indian longitudes. These enhancements occur following the typical monotonic decrease in emission intensity after sunset. The presence of poleward meridional wind preceded by cessation and reversal of equatorward wind at the post‐sunset hours was shown to be the cause for such observed emission enhancements in an earlier study. In this study, the cause of such reversal in meridional winds during post‐sunset hours has been investigated using the variation in electron densities and meridional winds simulated by the Whole Atmosphere Community Climate Model with thermosphere‐ionosphere eXtension (WACCM‐X), which also shows enhancements in electron densities similar to those observed in the post‐sunset OI 630.0 nm nightglow emissions, and simultaneous reversal in meridional winds as well. The amplitudes and phases of different components of tides obtained from WACCM‐X meridional winds reveal a significant contribution of higher‐order tides, especially, quarter‐diurnal tides, to the observed reversal in the meridional winds during post‐sunset hours.

Observations of ionospheric disturbances associated with the 2020 Beirut explosion by Defense Meteorological Satellite Program and ground-based ionosondes

Abstract. A major explosion that released a significant amount of energy into the atmosphere occurred in Beirut on 4 August 2020. The energy released may have reached the upper atmosphere and generated some traveling ionospheric disturbances (TIDs), which can affect radio wave propagation. In this study, we used data from the Defense Meteorological Satellite Program (DMSP) and ground-based ionosondes in the Mediterranean region to investigate the ionospheric response to this historic explosion event. Our DMSP data analysis revealed a noticeable increase in the ionospheric electron density near the Beirut area following the explosion, accompanied by some wavelike disturbances. Some characteristic TID signatures were also identified in the shape of ionogram traces at several locations in the Mediterranean. This event occurred during a period of relatively quiet geomagnetic conditions, making the observed TIDs likely to have originated from the Beirut explosion, not from other sources such as auroral activities. These observational findings demonstrate that TIDs from the Beirut explosion were able to propagate over longer distances, beyond the immediate areas of Lebanon and Israel–Palestine, reaching the Mediterranean and eastern Europe.

The Venus Global Ionosphere‐Thermosphere Model (V‐GITM): A Coupled Thermosphere and Ionosphere Formulation

AbstractThis paper introduces the new Venus global ionosphere‐thermosphere model (V‐GITM) which incorporates the terrestrial GITM framework with Venus‐specific parameters, ion‐neutral chemistry, and radiative processes in order to simulate some of the observable features regarding the temperatures, composition, and dynamical structure of the Venus atmosphere from 70 to 170 km. Atmospheric processes are included based upon formulations used in previous Venus GCMs, several augmentations exist, such as improved horizontal and vertical momentum equations and tracking exothermic chemistry. Explicitly solving the momentum equations allows for the exploration of its dynamical effects on the day‐night structure. In addition, V‐GITM's use of exothermic chemistry instead of a strong heating efficiency accounts for the heating due to the solar EUV while producing comparable temperatures to empirical models. V‐GITM neutral temperatures and neutral‐ion densities are compared to upper atmosphere measurements obtained from Pioneer Venus and Venus Express. V‐GITM demonstrates asymmetric horizontal wind velocities through the cloud tops to the middle thermosphere and explains the mechanisms for sustaining the wind structure. In addition, V‐GITM produces reasonable dayside ion densities and shows that the neutral winds can carry the ions to the nightside via an experiment advecting .

Global thermospheric mass density monitoring using LEO constellations: Simulation and analysis

Neutral thermospheric density is a crucial parameter for orbital tracking and upper atmosphere research. Here, we present a method to monitor global neutral thermospheric density testing simulations in various space environments with various satellite configurations and altitudes. The simulation results at 1° × 1° pixel resolution show that (1) within the range of 300–600 km orbital altitudes, the monitoring accuracy improves with the increase of the number of satellites, but this gain is significantly attenuated when the number of satellites increases to approximately 1,000; (2) the monitoring accuracy decreases with the increase of the altitude; and (3) the method presented in this study exhibits robustness under different space weather conditions. Furthermore, a differentiated satellite usage strategy (High Tightness and Low Looseness, HTLL) is developed to reduce the number of satellites used. Preliminary results indicate that the use of the HTLL method can reduce the number of satellites used from 2,592 to 1,044, whereas the maximum average relative deviation (ARD) does not exceed 1 %. The methods presented in this study have potential for future applications in the development of thermosphere research and satellite tracking.

Modeling of Nitric Oxide Infrared radiative flux in lower thermosphere: A machine learning perspective

Nitric Oxide (NO) significantly impacts energy distribution and chemical processes in the mesosphere and lower thermosphere (MLT). During geomagnetic storms, a substantial influx of energy in the thermosphere leads to an increase in NO infrared emissions. Accurately predicting the radiative flux of Nitric Oxide is crucial for understanding the thermospheric energy budget, particularly during extreme space weather events. With advancements in computational techniques, machine learning (ML) has become a highly effective tool for space weather forecasting. This effort becomes even more worthwhile considering the availability of two decades of continuous NO infrared emissions measurement by TIMED/SABER along with several other key thermospheric variables. We present the scheme of development of an ML-based predictive model for Nitric Oxide Infrared Radiative Flux (NOIRF). Various ML algorithms have been tested for better predictive ability, and an optimized model (NOEMLM) has been developed for the study of NOIRF. This model is able to extract the underlying relationships between the input features and effectively predict the NOIRF. The NOEMLM predictions have very good agreements with SABER observation during quiet time as well as geomagnetic storms. In comparison with the existing TIEGCM model, NOEMLM has very good performance, especially during extreme space weather conditions. The results of this study suggest that utilizing geomagnetic and space weather indices with ML/AI can serve as superior parameters for studying the upper atmosphere, as compared to focusing on specific species having complex chemical processes and associated uncertainties in constituents. ML techniques can effectively carry out the analysis with greater ease than traditional chemical studies.

NATURAL OR ARTIFICIAL TRITIUM IN RIVERS – THE ASSESSMENT USING SYMMETRICAL INDEX

Tritium, hydrogen isotope, with a half-life of 12.3 years, is produced in two ways: naturally and artificially. Naturally, tritium is generated through the interaction of cosmic radiation protons and neutrons with gases in the upper atmosphere. Artificially, tritium origins from the atmospheric nuclear tests, production from nuclear reactors, future fusion reactors, fuel reprocessing plants, heavy water production facilities and commercial production for medical diagnostics, radiopharmaceuticals, luminous paints. Elevated concentrations of tritium in the environment are of great public concern. Considering the fact that nuclear power plants are located on rivers, knowing the activity concentration of this isotope in rivers is of great importance. This work presents the results for tritium determination in Danube and Sava River in Belgrade, Serbia. The origin of tritium was estimated using a mathematical parameter, symmetrical index.

Radioactivity soundings of the upper atmosphere in Finland 1962-2022

Radioactivity soundings have been performed in Finland since the early 1960s to measure radiation and radioactivity levels in the atmosphere up to the altitude of almost 40 km. A sonde package based on a Geiger‐Müller (GM) tube is carried up to the stratosphere by a balloon filled with hydrogen or helium. En route the GM tube count rate values are sent to the ground station with a radio transmitter. These radioactivity soundings revealed the presence of abnormal radioactivity in the stratosphere over Finland due to Soviet atmospheric nuclear tests in 1962. Between 1964 and 1980 artificial radioactivity in the stratosphere originating from the Chinese nuclear tests were observed too. The radioactivity soundings have brought information on cosmic radiation even if the main motivation has been the surveillance of artificial radioactivity in the upper atmosphere. The effects of the solar cycle, geomagnetic latitude and solar proton events on the radiation environment of the upper atmosphere have been measured. The produced vertical ionization profiles may also be useful in studies concerning ion‐induced or ion‐mediated new particle formation events in the atmosphere.

Vertical shear instability with dust evolution and consistent cooling times

Context. Gas in protoplanetary disks mostly cools via thermal accommodation with dust particles. Thermal relaxation is thus highly sensitive to the local dust size distributions and the spatial distribution of the grains. So far, the interplay between thermal relaxation and gas turbulence has not been dynamically modeled in hydrodynamic simulations of protoplanetary disks with dust. Aims. We aim to study the effects of the vertical shear instability (VSI) on the thermal relaxation times, and vice versa. We are particularly interested in the influence of the initial dust grain size on the VSI and whether the emerging turbulence is sustained over long timescales. Methods. We ran three axisymmetric hydrodynamic simulations of a protoplanetary disk including four dust fluids that initially resemble MRN size distributions of different initial grain sizes. From the local dust densities, we calculated the thermal accommodation timescale of dust and gas and used the result as the thermal relaxation time of the gas in our simulation. We included the effect of dust growth by applying the monodisperse dust growth rate and the typical growth limits. Results. We find that the emergence of the VSI is strongly dependent on the initial dust grain size. Coagulation also counteracts the emergence of hydrodynamic turbulence in our simulations, as shown by others before. Starting a simulation with larger grains (100 μm) generally leads to a less turbulent outcome. While the inner disk regions (within ∼70 au) develop turbulence in all three simulations, we find that the simulations with larger particles do not develop VSI in the outer disk. Conclusions. Our simulations with dynamically calculated thermal accommodation times based on the drifting and settling dust distribution show that the VSI, once developed in a disk, can be sustained over long timescales, even if grain growth is occurring. The VSI corrugates the dust layer and even diffuses the smaller grains into the upper atmosphere, where they can cool the gas. Whether the instability can emerge for a specific stratification depends on the initial dust grain sizes and the initial dust scale height. If the grains are initially ≳100 μm and if the level of turbulence is initially assumed to be low, we find no VSI turbulence in the outer disk regions.

Моделирование влияния вариаций солнечной активности на глобальную атмосферную циркуляцию

In this study, we continue a series of works devoted to modeling and studying the sensitivity of global atmospheric dynamic processes to variations in solar emissions during the 11-year solar activity (SA) cycle. We focus on studying the response of meridional atmospheric circulation in the middle atmosphere to changes in thermosphere characteristics with changes in SA. For this purpose, numerical simulations of the general atmospheric circulation were carried out using the nonlinear numerical circulation model of the middle and upper atmosphere MUAM. The main mechanism of the influence of thermospheric disturbances on the underlying layers is assumed to be a change in the conditions of propagation and reflection of planetary waves (PWs) due to changes in SA. Changes in temperature, zonal and meridional wind are shown to localize along waveguides, demonstrating the significant role of PWs in transmitting thermospheric disturbances, caused by changes in SA, to the middle atmosphere. The magnitude of changes in meridional circulation can reach 10 % in the northern stratosphere between SA maxima and minima.

Modeling the impact of solar activity variations on global atmospheric circulation

In this study, we continue a series of works devoted to modeling and studying the sensitivity of global atmospheric dynamic processes to variations in solar emissions during the 11-year solar activity (SA) cycle. We focus on studying the response of meridional atmospheric circulation in the middle atmosphere to changes in thermosphere characteristics with changes in SA. For this purpose, numerical simulations of the general atmospheric circulation were carried out using the nonlinear numerical circulation model of the middle and upper atmosphere MUAM. The main mechanism of the influence of thermospheric disturbances on the underlying layers is assumed to be a change in the conditions of propagation and reflection of planetary waves (PWs) due to changes in SA. Changes in temperature, zonal and meridional wind are shown to localize along waveguides, demonstrating the significant role of PWs in transmitting thermospheric disturbances, caused by changes in SA, to the middle atmosphere. The magnitude of changes in meridional circulation can reach 10 % in the northern stratosphere between SA maxima and minima.