Middle Latitudes Research Articles

Body Temperature Patterns and Energy Balance Hormones in Free-Living Thirteen-Lined Ground Squirrels (Ictidomys tridecemlineatus) from Different Latitudes.

AbstractThis article examines hormone concentrations and body temperature (Tb) patterns of free-living thirteen-lined ground squirrels (TLGSs) across the majority of their latitudinal range in the United States (from Texas to Minnesota). Free-living TLGSs () were implanted with Tbdata loggers in 2019 before they entered hibernation. Three adult female TLGSs, one each from Oklahoma (low latitude), Iowa (middle latitude), and Minnesota (high latitude), were recaptured in 2020 after the hibernation season. Although this provides an n of 1 for each location and therefore no statistically supported conclusions can be drawn, the hibernation season was longest in the animal from the highest latitude with coldest winter soil temperatures (Minnesota) and shortest in the animal retrapped at the lowest latitude (Oklahoma). Torpor bouts were generally longer when soil temperatures were lower. The Iowa and Minnesota squirrels had a prolonged period of short torpor bouts with Tb near 20°C at the beginning of the hibernation season. Concentrations of the orexigenic hormone ghrelin and the sex hormones estradiol and testosterone were also compared in populations from different latitudes. In general, Minnesota males had higher testosterone than males from other populations, possibly due to a later breeding season relative to other squirrel populations. Animals trapped in early summer had significantly lower concentrations of ghrelin than those captured in midsummer, potentially driving the fat-storing period before the hibernation season. Together, these results suggest latitudinal variation in physiological regulation of circannual rhythms.

Comparative Study of the Es Layer between the Plateau and Plain Regions in China

The lower atmosphere forcing plays an important role in forming the sporadic E (Es) layer in the ionosphere. In this study, a comparative study of the Es layer recorded by ionosondes at the middle latitude regions was carried out between the plateau and plain regions in China. The two ionosonde stations (Zhangye, 39.21°N, 100.54°E and Beijing, 40.25°N, 116.25°E) are located at the Qinghai–Tibet Plateau and North China Plain, respectively. The data during the year 2018 were used to reveal the characteristics of the Es layer. The occurrence probability, the critical frequency (foEs) and the base virtual height (h’Es) were considered in this study. Results show that: (1) The diurnal and seasonal variations of the occurrence probability between these two regions are similar. The maximum occurrence probability is at noontime and in the summer season. However, the Es at Zhangye occurred more frequently than Beijing at nighttime and in winter to early spring. (2) Similar to previous studies, the maximum value of foEs at Beijing mainly occurred in summer. Interestingly, the maximum value is in winter at Zhangye station. (3) The characteristics of the anomaly of the Es layer at Zhangye are mostly consistent with the characteristics of atmospheric gravity waves in the Qinghai–Tibet Plateau. Therefore, compared with observations at Beijing, the anomalies of the Es layer at Zhangye (at night and in winter to spring) might be attributed to gravity waves in the lower atmosphere over the Qinghai–Tibet Plateau.

Weighted Mean Annual Rain Height Applied to Rain Attenuation Prediction on Earth-Space Links

Rain height is crucial for rain attenuation prediction along slant paths, such as Earth-space links. The global digital map of the mean annual rain height is given in Recommendation ITU-R P.839-4. The disadvantage of this model is that heavy rainfall in most regions of the middle and high latitudes of the world is typically concentrated over a few months, such as summer in North China, and the mean rain height during these months and the mean annual rain height are often significantly different. In this study, a new weighted mean annual rain height is proposed by using the ratio of the mean monthly rainfall to the mean annual rainfall as the weight. The analysis shows that the weighted mean annual rain heights have been closer to the statistical rain heights during heavy rainfall in general. On the other hand, the work of this paper helps to improve the accuracy of the rain attenuation prediction model on Earth-space links in China. However, the weighted mean annual rain heights have different characteristics for different rainfall climate zones. This study will contribute to the research of rain attenuation modelling on Earth-space links.

Freeze-thaw alternations accelerate plasticizers release and pose a risk for exposed organisms

The application of plastic mulch films brings convenience to agricultural production, but also causes plastic waste that can be degraded into microplastics (MPs). However, little is known about the fate of plastic waste in agricultural ecosystem under freeze-thaw alternation in middle and high latitudes, as well as in highlands around the world. Whether the release of plasticizers, i.e. phthalate esters (PAEs), under such conditions would pose a potential risk to exposed organisms due to bioaccumulation is also unknown. To fill these data gaps, the agricultural fields in Liaoning of China with typical freeze-thaw alternation was selected as the study area. The transformation of plastic film was demonstrated by simulation freeze-thaw alternating from −30 to 20 ℃. Soil samples were collected to investigate the patterns of MP composition, abundance, and distribution. Concurrently, the concentrations of two PAEs including bis(2-ethylhexyl) phthalate (DEHP) and diethyl phthalate (DEP) in soils were analyzed to provide information on the correlation between MPs abundance and PAEs concentrations as well as potential risks. The results showed that freeze-thaw alternating can accelerate the formation of MPs and release of PAEs from plastic waste. The abundance of MPs was positively correlated with the concentration of PAEs. Soil PAEs ranged from 3268 ± 213–6351 ± 110 μg/kg, indicating that over 40 % of the PAEs were transferred from plastic films to soils. Such residual amounts could pose risk for exposed organisms. Hence, the current study suggested that special concerns should be given to the release plasticizers in plastic waste of agricultural soils.

Calcification, Dissolution and Test Properties of Modern Planktonic Foraminifera From the Central Atlantic Ocean

The mass of well-preserved calcite in planktonic foraminifera shells provides an indication of the calcification potential of the surface ocean. Here we report the shell weight of 8 different abundant planktonic foraminifera species from a set of core-top sediments along the Mid-Atlantic Ridge. The analyses showed that near the equator, foraminifera shells of equivalent size weigh on average 1/3 less than those from the middle latitudes. The carbonate preservation state of the samples was assessed by high resolution X-ray microcomputed tomographic analyses of Globigerinoides ruber and Globorotalia truncatulinoides specimens. The specimen preservation was deemed good and does not overall explain the observed shell mass variations. However, G. ruber shell weights might be to some extent compromised by residual fine debris internal contamination. Deep dwelling species possess heavier tests than their surface-dwelling counterparts, suggesting that the weight of the foraminifera shells changes as a function of the depth habitat. Ambient seawater carbonate chemistry of declining carbonate ion concentration with depth cannot account for this interspecies difference. The results suggest a depth regulating function for plankton calcification, which is not dictated by water column acidity.

Evolution of ice sheets on early Mars with subglacial river systems

Geological observations have revealed that early Martian terrains were carved with by numerous networks of valleys, which provides evidence that prolonged water activity sculpted the ancient surface of Mars during the late Noachian and the early Hesperian ages. Although such geological records would in theory require a large volume of liquid water under a long-term stable “warm and wet” climate, several model studies have indicated a contrasting “cold and icy” climate in early Mars, such that the formation of large-scale ice sheets on highlands would provide a vast reservoir of meltwater. In this study, we developed a global ice sheet model, named ALICE (Accumulation and ablation of Large-scale ICE-sheets with dynamics and thermodynamics) to perform the first simulation of the evolution of ice sheets coupled with a paleo-Mars global climate model. We began our calculations of glacial formation from the initial state with the ocean water amount corresponding to a 500 m global equivalent layer (GEL) for “cool and wet” atmospheric conditions with a surface pressure of 2 bar, H2 mixing ratios of 0% and 3%, and obliquities of 20°, 40°, and 60°.Our results show that all the water of the ocean and lakes were transferred to ice sheets within ~105 Mars years, and extensive ice sheets (thousands of meters in thickness) were formed in the southern low to middle latitudes. When geothermal heat flux was suitably high and the atmosphere contained 3% of H2, continuous subglacial melting supplied enough water due to widespread temperate-based ice sheets, forming runoff systems in the southern highlands where most valley networks are observed. With an obliquity of 40°, meltwater carved early Martian terrains within a relatively brief geological timescale (~105 Mars years). We also revealed that CO2 only atmosphere (H2 mixing ratio of 0%) could not reproduce temperate-based ice sheets and subglacial erosions even with assumed higher geothermal heat fluxes. There is still a possibility that several valleys were produced by short-lived climatic warming events, such as volcanism and meteorite impacts, which could produce the vast amount of meltwater required to sculpt valley systems.

Secular variations on the North American tectonic plate

Based on the results of geomagnetic observatories located near the North magnetic pole and in the middle latitudes of the North American tectonic plate, the secular variations (SV) of the Earth’s geomagnetic field have been studied. The influence of solar activity on SV on the North American plate has been shown.
 The author has identified the SV source of non-dipole origin with a period of about 22 years. The source did not affect SV in the XX—XXI cycle of solar activity probably due to the influence of the SV jerk, but it showed itself well in the XXII—XXIV cycles of solar activity. It is demonstrated that the influence of the SV source increases with increasing latitude of the observatory and is almost imperceptible at low latitudes.
 According to the Minuk observatory and others, a 100-year cycle of age-related variation has been identified — the early 20th century: a maximum took place in the 1960s and cycle termination was in 2013.
 Following the observatories located on the eastern part of the plate, the SV acceleration triggered by the influence of the Atlantic focus has been calculated. The research identifies that the «activation» of the SV Atlantic focus occurs with an expansion in the number of recurrent geomagnetic storms, which is evidenced in odd cycles of solar activity (the VMS direction from the Sun).
 According to observatories located near the Pacific Plate (west coast of North America), the impact of the Atlantic focus on SV is not as pronounced as in the eastern part. However, there is an influence of the non-dipole SV source depending on the observatory’s latitude and solar activity.

Diurnal and Seasonal Characteristics of the Longitudinal Variations of Electron Densities in the Topside Ionosphere at Middle Latitudes

AbstractThe ionosphere experiences strong diurnal and seasonal changes. The longitudinal variations of electron density (Ne) in the ionosphere at the middle latitudes also show strong diurnal and seasonal changes. In this paper, we use in situ Ne measurements from the DEMETER satellite and electron density profiles retrieved from the COSMIC data to study the local time (LT) and seasonal dependence of the longitudinal variations of topside Ne at middle latitudes during 2007–2009. With regard to the diurnal trend, the reversal phase of longitudinal peaks/valleys of topside Ne with a 12 hr interval occurred in less than half of the cases, and there were less cases with eastward phase shift of the longitudinal variations of topside Ne with LT in winter than those in other seasons. The seasonal trends of transition longitudes of topside Ne might be westward from winter to summer and eastward from summer to winter in the daytime and in the opposite direction at night in both hemispheres in some cases and sometimes they were located within 20° of longitude at 52°N in other cases. The longitudinal peaks/valleys of hmF2 and/or NmF2 and the longitudinal peaks/valleys of topside Ne were within 30° of longitude in most cases at all local times, in all seasons, and in both hemispheres. Exceptions to this were independent of season or LT.

Effects of CME-induced Geomagnetic Storm on Geomagnetic Induced Current at High and Middle Latitudes

Geomagnetic storm has been one of greatest events in space weather studies. Apart from the formation of aurora, geomagnetic induced current (GIC) is also induced during the storm when the storm intensity gets severe. Coronal mass ejection (CME) is a massive eruption created by the Sun and is believed to be the driver of geomagnetic storm. This paper is aimed to examine the effects of CME-induced geomagnetic storm on geomagnetic induced current (GIC) at high and middle latitudes by studying four levels of storm: minor (Kp 5), moderate (Kp 6), strong (Kp 7) and severe (Kp 8). We applied qualitative analysis through descriptive approach to describe the relationship between the storm intensity and GIC activity. Since the exact value of GIC were inaccessible, we adopted horizontal component time derivative magnetic field (dH/dt) as the indicator for GIC activity. At the end of the study, we found that the GIC highly depends on the storm intensity, by which higher levels of storm triggers more actively induced current. Besides, high latitude ionosphere was showing strong reactions to the storm arrival compared to middle latitude ionosphere as the magnitudes of dH/dt recorded by Barrow station at high latitude fluctuated within wider and higher range.

Morphological features of heliogeophysical conditions leading to the appearance of geomagnetically induced currents on the territory of Kazakhstan

Morphological features of helio-geophysical conditions leading to the appearance of geomagnetically induced currents at mid-latitudes are determined. Using the example of a very large geomagnetic storm with a sudden onset that occurred on May 10-15, 2021, the morphological features of the helio-geophysical conditions leading to the appearance of geomagnetically induced currents at mid-latitudes are described. To describe this heliogeophysical event, satellite observations with high time resolution (5 minutes) for various parameters of the solar wind, data on interplanetary and geomagnetic indices were used. Geomagnetically induced currents can be introduced into the network and cause many adverse consequences. The vulnerability of major electric power systems to such events has increased over the past few decades as the transmission lines of the power grid have become more interconnected and increased in length. In this paper, the morphological features of the helio-geophysical conditions leading to the appearance of geomagnetically induced currents at middle latitudes are determined. Thus, using the example of a very large geomagnetic storm with a sudden onset that occurred on May 10-15, 2021, a description is given of the morphological features of the helio-geophysical conditions leading to the appearance of geomagnetically induced currents at mid-latitudes.

Improved Field‐Aligned Current and Radial Current Estimates at Low and Middle Latitudes Deduced by the Swarm Dual‐Spacecraft

AbstractIonospheric currents have widely been investigated by using magnetic measurements from low‐Earth orbiting satellites. However, the assumptions of deriving currents from the magnetic measurements have not always been well considered. In this study we performed a detailed analysis of the ionospheric radial current (IRC) and inter‐hemispheric field‐aligned current (IHFAC) estimates at equatorial and low latitudes derived from the single‐satellite and dual‐spacecraft (dual‐SC) approaches of European Space Agency (ESA's) Swarm constellation. Data considered cover a 5‐year period, from 17 April 2014 to 16 April 2019. We found for most of the cases, the IRCs and IHFACs derived from both approaches show consistent latitudinal profiles. However, there are several cases with discrepancy exceeding 5 nA/m2 between two approaches. On average, the diurnal variations of IHFACs from both approaches agree well with each other for all seasons. But the amplitudes of single‐satellite results reach only about 70% of those from the dual‐SC. This difference is attributed to the fact that only the magnetic field By component is utilized in the single‐satellite approach, while both Bx and By components are considered in the dual‐SC approach. Above the magnetic equator, the IRCs derived from single‐satellite approach show clear tidal signatures, while such signature cannot be found in the IRCs from dual‐SC approach. We interpret these tidal‐signature of IRCs as spurious results, caused by equatorial electrojet contributions to the ∆By component. The dual‐SC derived IRCs show notable differences between ascending and descending orbits. Such differences might be due to a violation of the assumed perfect calibration of Swarm A and C. We suggest a systematic spacecraft‐fixed bias in the along‐track magnetic field component (Bx) between Swarm A and C. By interpreting the IRC differences, we obtain bias values of ∆Bx reaching 1 nT. Our results reveal that ionospheric currents are better characterized by the dual‐SC approach. But comparison with single‐satellite current estimates can help to identify weakness.

Driving Influences of the Doppler Flash Observed by SuperDARN HF Radars in Response to Solar Flares.

Sudden enhancement in high‐frequency absorption is a well‐known impact of solar flare‐driven Short‐Wave Fadeout (SWF). Less understood, is a perturbation of the radio wave frequency as it traverses the ionosphere in the early stages of SWF, also known as the Doppler flash. Investigations have suggested two possible sources that might contribute to it’s manifestation: first, enhancements of plasma density in the D‐and lower E‐regions; second, the lowering of the F‐region reflection point. Our recent work investigated a solar flare event using first principles modeling and Super Dual Auroral Radar Network (SuperDARN) HF radar observations and found that change in the F‐region refractive index is the primary driver of the Doppler flash. This study analyzes multiple solar flare events observed across different SuperDARN HF radars to determine how flare characteristics, properties of the traveling radio wave, and geophysical conditions impact the Doppler flash. In addition, we use incoherent scatter radar data and first‐principles modeling to investigate physical mechanisms that drive the lowering of the F‐region reflection points. We found, (a) on average, the change in E‐ and F‐region refractive index is the primary driver of the Doppler flash, (b) solar zenith angle, ray’s elevation angle, operating frequency, and location of the solar flare on the solar disk can alter the ionospheric regions of maximum contribution to the Doppler flash, (c) increased ionospheric Hall and Pedersen conductance causes a reduction of the daytime eastward electric field, and consequently reduces the vertical ion‐drift in the lower and middle latitude ionosphere, which results in lowering of the F‐region ray reflection point.

In-Motion Coarse Alignment Method for SINS/GPS Integration in Polar Region

In this article, an in-motion coarse alignment method in the polar region is proposed. Different from the traditional coarse alignment method, the vector observation is constructed with the grid frame. Thus, the calculated singularity in the polar region, which is easy to see in the navigational frame, is suppressed. Considering the GPS measurements, the velocity errors are assumed in the GPS measurements. Since the characteristics of the observation vectors, the initial velocity error always exists during the whole alignment process. To address the initial velocity error, a simple method with the vector subtraction operation is used to construct the new observation vector. In the new observation vector, the initial velocity is eliminated. Thus, the initial velocity error is suppressed. To verify the performance of the proposed method, a virtual polar region method is proposed to transform the experimental data of the field tests in the low and middle latitude region. The simulation and field tests are shown that the proposed method can get more accurate alignment results than the traditional methods.

Instantaneous Achievement of the Hall and Pedersen–Cowling Current Circuits in Northern and Southern Hemispheres During the Geomagnetic Sudden Commencement on 12 May 2021

The present article aims at a consistent understanding of observation, theoretical model, and simulation with the geomagnetic sudden commencement (SC) observed in the morning and afternoon at high and middle latitudes in the northern and southern hemispheres and at the noontime equator on 12 May 2021. The SC in Bx- and By-components of the geomagnetic field, SCx,y, was composed of the positive/negative preliminary (PI) and main impulses (MI) as SCx (+ -) and SCy (- +) in the morning and SCx (- +) and SCy (+ -) in the afternoon at middle latitudes in the northern hemisphere. SCx in the southern hemisphere is in the same polarity as those in the northern hemisphere, except for SCx (+ +) in the morning. SCy in the southern hemisphere has reverse polarity to those in the northern hemisphere. The PIx in the northern hemisphere matches the well-established two-cell Hall current vortices with anti-clockwise and clockwise directions in the morning and afternoon, respectively, and the MIx matches reverse Hall current vortices. The PIx and MIx in the southern hemisphere meet the Hall currents that are mirror images of those in the northern hemisphere with respect to the equator except for the positive MI in the morning. The PIy in the northern hemisphere is shown to meet the northward and southward Pedersen currents in the morning and afternoon, respectively, and the MIy meets reverse Pedersen currents. The PIy and MIy in the southern hemisphere are found to meet the Pedersen currents that are mirror images of those in the northern hemisphere. At the equator, typical SCx (- +) is observed, meeting the Cowling currents that should be supplied by the Pedersen currents responsible for the observed midlatitude SCy in the northern and southern hemispheres. The electric fields of the PI and MI observed by the HF Doppler sounders at the middle latitudes in the northern hemisphere are westward and eastward, respectively, in both the morning and afternoon, meeting the conventional dusk-to-dawn PI and dawn-to-dusk MI electric fields. The onset of the PI is found to be simultaneous with the resolution of a few seconds from high latitude to the equator in both the northern and southern hemispheres, indicating instantaneous achievement of the Pedersen–Cowling currents from high latitude to the equator. The instantaneous achievement of the energy-consuming Pedersen–Cowling currents is explained by the TM0/TEM mode wave in the Earth-ionosphere waveguide/transmission line rather than the compressional waves in the magnetosphere and F-region ionosphere. REPPU (REProduce Plasma Universe) global simulation model equipped with a potential solver at the inner boundary of the model magnetosphere reproduces the PI and MI electric fields at middle latitudes and SCx (- +) at the dayside equator. The simulation results are found to be consistent with most features of observations, such as the time scale of PI and MI, direction of the midlatitude electric field and generation of the Cowling currents. The simulation proves that the electric fields and FACs are generated in the outer magnetosphere, transmitted to the polar ionosphere and then to the equator in the Pedersen–Cowling current circuit.

Low- and Mid-Latitude Ionospheric Response to the 2013 St. Patrick’s Day Geomagnetic Storm in the American Sector: Global Ionosphere Thermosphere Model Simulation

In this study, the low-and mid-latitude ionospheric response to the main phase of the 2013 St. Patrick’s Day geomagnetic storm in the American sector on the dayside has been investigated using the ground-based measurements and the Global Ionosphere Thermosphere Model (GITM). First, it is found that the observed ionospheric response can be well reproduced by GITM when it is driven by the electric potential and electron precipitation patterns derived from the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) technique. The AMIE-driven GITM simulation also significantly improves the data-model comparison as compared with the simulation driven by the high-latitude empirical models. Second, it is found that the transport process associated with the neutral wind is largely responsible for the observed ionospheric response. Specifically, the traveling atmospheric disturbances (TADs) propagating from the opposite hemisphere play an important role in the formation of the negative storm phase at low and middle latitudes. Third, it is found that the asymmetric negative storm phases occurred at the nominal equatorial ionization anomaly (EIA) peak region in the afternoon sector are mainly attributed to the interaction of the TADs launched in different hemispheres with different phase speeds. Specifically, stronger Joule heating deposited in the northern hemisphere (NH) generates TADs with faster phase speeds than those launched in the southern hemisphere (SH). Consequently, the locations where the TADs originated from the different hemispheres interact are asymmetric about the geomagnetic equator, leading to the formation of asymmetric ionospheric negative storm phases. This study highlights the importance of accurately specifying high-latitude electrodynamic forcings in global I-T simulations and provides a new insight into the cause of the interhemispheric asymmetry phenomena during geomagnetic storms.

Global exacerbation of episodic local vegetation greenness decline since the 21st century

Extreme climate-induced vegetation greenness decline significantly affects the stability of ecosystem function. Extreme climate events have occurred frequently in the recent 20 years and the possibility of climate anomalies is forecasted to increase in the future. But currently, the spatial and temporal response of episodic local vegetation decline to climate extremes at a global scale are still unclear. In this study, the detrend NDVI data was utilized as the indicator of vegetation growth, and a spatiotemporally contiguous recognition method was proposed to identify episodic large-scale vegetation decline events globally, subsequently, the spatiotemporal characteristics of these vegetation decline events and their interannual variation trends during 2000–2019 were explored. The results showed that (1) the spatiotemporally contiguous recognition method proposed by this paper was proven to be accurate in identifying the hotspot regions of large-scale vegetation decline. A total of 243 large-scale vegetation decline events were recognized globally during 2000–2019 drived by the method. (2) The global hotspots of large-scale vegetation decline were mainly distributed in the low-elevation areas at middle and low latitudes, especially at 15°S ~ 35°S, 15°N and 35°N, where covered north-western Africa, the Sahel, the Middle East, Central Asia, western India, the border of north-eastern China and Mongolia, western and south-central United States, northern Mexico, southern Africa, Australia, and southern and north-eastern South America. (3) Recent global episodic local vegetation decline has increased significantly since 2000, at the rate of 180,000 km2 of vegetation decline areas increasing per year. Particular, the severity of vegetation decline grew significantly since 2010 at the regions where covered the latitudes of approximately 15°N, 30°N and 65°N. Additionally, the severity of vegetation decline ranging from 20°S to 30°S weakened significantly since 2010. These findings were expected to provide the valuable scientific understanding for global vegetation decline and ecosystem responses to frequent climate extremes.

The Response of Geomagnetic Daily Variation and Ionospheric Currents to the Annular Solar Eclipse on 21 June 2020

AbstractIn this study, we examined the response of geomagnetic daily variation and ionospheric currents to the solar annular eclipse that passed through China at 10:00–17:30 LT on 21 June 2020. We utilized geomagnetic field data obtained from the Geomagnetic Network Center of China, Institute of Geophysics, China Earthquake Administration and International Real‐time Magnetic Observatory Network, which extend from middle latitudes to equatorial regions in China and surrounding areas. It is found that the eclipse obscuration reduces the intensity of geomagnetic daily variation at most stations as compared with the 5‐quiet‐day average. The response of geomagnetic daily variation to the solar eclipse depends on local time and latitude. In most shadowed areas of the eclipse, there is a reduction of northward (southward) component of the meridional magnetic daily field (ΔX) below (above) ∼30° magnetic latitudes. The solar eclipse can also induce a decrease of the zonal magnetic field variation (ΔY). Meanwhile, we observed that the solar eclipse reduces the intensity of vertical geomagnetic component (ΔZ) at the stations around the early afternoon aside the eclipse totality. In general, these geomagnetic responses imply that the solar eclipse can reduce the ionospheric solar quiet (Sq) current system. These ionospheric currents and ground geomagnetic field disturbances during the solar eclipse are also verified by a global physical model. The simulation demonstrates that the ionospheric currents in the southern hemisphere, where the solar eclipse does not cover, also have a weak response. Overall, the ionospheric current disturbance induced by the solar eclipse shows a counter‐Sq pattern.

Geomagnetic disturbances reduce heart rate variability in the Normative Aging Study

BackgroundSolar and geomagnetic activity (GA) have been linked to increased cardiovascular (CVD) events. We hypothesize that heart rate variability (HRV) may be the biological mechanism between increased CVD risk and intense geomagnetic disturbances (GMD). MethodsTo evaluate the impact of GA and intense GMD on HRV in 809 elderly men [age mean 74.5 (SD = 6.8)] enrolled in the Normative Aging Study (Greater Boston Area), we performed repeated-measures using mixed-effects regression models. We evaluated two HRV outcomes: the square root of the mean squared differences of successive normal-to-normal intervals (r-MSSD) and the standard deviation of normal-to-normal heartbeat intervals (SDNN) in milliseconds (ms). We also compared the associations between Kp and HRV in patients with and without comorbidities such as diabetes and coronary heart diseases (CHD). We used data on global planetary K-Index (Kp) from middle latitudes as a GA and GMD (>75th Kp) parameters from the National Oceanic and Atmospheric Agency's Space Weather Prediction Center. ResultsWe found a near immediate effect of continuous and higher Kp on reduced HRV for exposures up to 24 h prior to electrocardiogram recording. A 75th percentile increase in 15-hour Kp prior the examination was associated with a −14.7 ms change in r-MSSD (95 CI: −23.1, −6.3, p-value = 0.0007) and a −8.2 ms change in SDNN (95 CI: −13.9, −2.5, p-value = 0.006). The associations remained similar after adjusting the models for air pollutants over the exposure window prior to the event. In periods of intense GMD, the associations were stronger in patients with CHD and non-diabetes. ConclusionsThis is the first study to demonstrate the potential adverse effects of geomagnetic activity on reduced heart rate variability in a large epidemiologic cohort over an extended period, which may have important clinical implications among different populations.

Palynostratigraphical analysis of the late Maastrichtian – early Danian in the Gaviotín Formation, Punta del Este Basin, Uruguay

Palynological analysis were carried out for the uppermost Cretaceous – lowermost Palaeogene in the Gaviotín well, which was drilled in the marginal area of the offshore Punta del Este Basin (Uruguay). The studied interval (from 1582 to 1884 m) corresponds to the lower and middle parts of the Gaviotín Formation and the upper part of the underlying Mercedes Formation. The samples provided assemblages dominated by fairly well preserved organic walled dinoflagellate cysts. A total of 117 taxa were identified, several of them are recorded for the first time in the basin. The purpose of this study is to typify the uppermost Cretaceous – lowermost Palaeocene marine sediments of the Punta del Este Basin, which are part of the Gaviotín Formation, focused on their stratigraphical and palynological characteristics. According to the lithology, well logs and microfossil content, three intervals were recognized. The upper part of Mercedes Formation was deposited in a deltaic environment. The lower part of the Gaviotín Formation represents a shallow marine environment. The analysis of the middle part of the Gaviotín Formation (i.e. the upper part of the interval here studied) also reflects shallow marine conditions. Abrupt lithological changes around 1700 m depth, along with a sonic shift probably corresponding to a paraconformity and some biostratigraphical events allowed us to suggest that the K/Pg transition might be close to this depth. These assemblages bear several species that characterize the upper Maastrichtian – Danian interval in many sites from low, middle and high latitudes studied with high sampled resolution. These records demonstrate that the dinoflagellate provincialism suggested more than four decades ago for the Campanian cannot be recognized for successions younger than Maastrichtian. Our results permit the definition of a biostratigraphy that will assist drilling and hydrocarbon exploration in this and other mid-latitude Southwestern Atlantic basins.

Global, regional and seasonal analysis of total ozone trends derived from the 1995–2020 GTO-ECV climate data record

Abstract. We present an updated perspective on near-global total ozone trends for the period 1995–2020. We use the GOME-type (Global Ozone Monitoring Experiment) Total Ozone Essential Climate Variable (GTO-ECV) satellite data record which has been extended and generated as part of the European Space Agency's Climate Change Initiative (ESA-CCI) and European Union Copernicus Climate Change Service (EU-C3S) ozone projects. The focus of our work is to examine the regional patterns and seasonal dependency of the ozone trend. In the Southern Hemisphere we found regions that indicate statistically significant positive trends increasing from 0.6 ± 0.5(2σ) % per decade in the subtropics to 1.0 ± 0.9 % per decade in the middle latitudes and 2.8 ± 2.6 % per decade in the latitude band 60–70∘ S. In the middle latitudes of the Northern Hemisphere the trend exhibits distinct regional patterns, i.e., latitudinal and longitudinal structures. Significant positive trends (∼ 1.5 ± 1.0 % per decade) over the North Atlantic region, as well as barely significant negative trends (−1.0 ± 1.0 % per decade) over eastern Europe, were found. Moreover, these trends correlate with long-term changes in tropopause pressure. Total ozone trends in the tropics are not statistically significant. Regarding the seasonal dependence of the trends we found only very small variations over the course of the year. However, we identified different behavior depending on latitude. In the latitude band 40–70∘ N the positive trend maximizes in boreal winter from December to February. In the middle latitudes of the Southern Hemisphere (35–50∘ S) the trend is maximum from March to May. Further south toward the high latitudes (55–70∘ S) the trend exhibits a relatively strong seasonal cycle which varies from 2 % per decade in December and January to 3.8 % per decade in June and July.