Short-lived Events Research Articles

Personal Ornaments and Burial Rites in Prehistory

Archaeological burial contexts are among particularly attractive topics for both experts – archaeologists, and wider audiences. The reasons behind this are partially the rich, attractive portable finds that are usually associated with these contexts, but also the interpretative potential, i.e., insight into rituals and symbolic values of people in the past. Archaeological finds from burial contexts are very diverse in their nature and function, and may include parts of burial constructions, remains of rituals, objects placed along the deceased and objects placed on the deceased. The interpretation of burial contexts and associated finds are tightly connected and interlinked. These finds were often regarded as a result of a single, short-lived event and were considered as particularly important for the questions of relative and absolute chronology; the contents of burial finds were used as a basis for hypotheses regarding social relations, and, overall, burial finds were used for interpreting the identity of the deceased, reconstructing rituals, etc. Personal ornaments are particularly common in burial contexts, and, at the same time, the richest finds of personal ornaments mainly originate from burial contexts. When it comes to personal ornaments, it is usually assumed that they were owned by the deceased, and they are interpreted through the prism of status, prestige, and/or identity. However, personal ornaments might have had a much wider symbolic meaning. In this paper, we will look at the possibilities in terms of the meanings of personal ornaments from prehistoric contexts – beside markings of identity and status of the deceased, they might also have represented a gift to the deceased, gift to divinities, they might have had an apotropaic and a prophylactic function, for both the deceased and the participants in the burial ritual, and they might also have had an emotional meaning.

Paleomagnetic study of Tres Vírgenes Volcanic Complex, Baja California, Mexico

While the great majority of paleomagnetic studies come from Central Mexico (Trans Mexican Volcanic Belt), still few works are available from Baja California peninsula. Twelve lava and domes from the Tres Vírgenes Volcanic Complex were sampled, and 96 standard paleomagnetic cores were analyzed. Available isotope ages range from 22 ka to 300 ka. Magnetic mineralogy analysis indicates that titanium-poor titanomagnetite is the main carrier of remanent magnetization, although some sites also contain Ti-rich titanomagnetites commonly observed in recent volcanic eruptions. Nine of the studied lavas yielded normal polarity magnetization with site mean declination ranging D=349°−28.1° and inclination I=32.4°−55.4° as expected for the Bruhnes chron. Mean paleodirections show remarkable coincidence with previously reported data from the nearby San Quintín volcanic field. The scatter parameter of the virtual geomagnetic poles SB=15.1213.8716.60 agrees, under uncertainties, with the latitude-dependent G Model of paleosecular variation for the Bruhnes chron. Both Thellier double heating and Tsunakawa-Shaw absolute paleointensity methods were applied, however, the success rate was relatively low with 4 reliable values ranging from 21.46μTto56.4μT. One of the lava domes that we dated at 253 ± 24 ka using the U-Th systematics demonstrated the worldwide observed Calabrian Ridge 0 short-lived geomagnetic event.

Impact of Paleocene–Eocene tectonic and climatic forcing on Arctic sediment transfer variability: SW Barents Sea, Norway

During the Paleocene and Eocene, many Arctic basins experienced multiple, yet synchronous periods of increased sedimentation rates. Several causal factors have been suggested including major volcanic events, tectonic plate reorganization and plate break-up, as well as widespread uplift along with contemporaneous and short-lived hyperthermal events. However, the significance of and relation between tectonic and climatic forcing on Arctic sediment transfer during the early Paleogene is poorly understood. In this case study from the Barents Shelf margin in the Norwegian Arctic, we present previously unpublished cores combined with exploration wells, and new high-resolution 3D seismic data to investigate sedimentary stacking patterns and geomorphological features in the Sørvestsnaget Basin. Our integrated investigations reveal the development of climate-controlled and tectonically-driven submarine fans. The PETM fans display an individual fan as a result of single depositional event compared to the middle Eocene fans that show stacked submarine fans probably deposited during multi-phase events. Our Stratigraphic Forward Modelling analysis indicates that regional-scale tectonically induced uplift significantly increased the amount of sand delivered to the basin as documented by a thickening of the basin fill succession. The climatic component contributes to sand transport variability to the basin, and thus the temporal evolution pattern of sand is much varied. Finally, we discuss our findings with the tectonic and climatic forcing factors in a circum-Arctic perspective.

Studies on Heavy Precipitation in Portugal: A Systematic Review

This systematic review, based on an adaptation of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement from 2020, focuses on studies of the atmospheric mechanisms underlying extreme precipitation events in mainland Portugal, as well as observed trends and projections. The 54 selected articles cover the period from 2000 to 2024, in which the most used keywords are “portugal” and “extreme precipitation”. Of the 54, 23 analyse trends and climate projections of precipitation events, confirming a decrease in total annual precipitation, especially in autumn and spring, accompanied by an increase in the frequency and intensity of extreme precipitation events in autumn, spring and winter. Several articles (twelve) analyse the relationship between synoptic-scale circulation and heavy precipitation, using an atmospheric circulation types approach. Others (two) establish the link with teleconnection patterns, namely the North Atlantic Oscillation (NAO), and still others (three) explore the role of atmospheric rivers. Additionally, five articles focus on evaluating databases and Numerical Weather Prediction (NWP) models, and nine articles focus on precipitation-related extreme weather events, such as tornadoes, hail and lightning activity. Despite significant advances in the study of extreme precipitation events in Portugal, there is still a lack of studies on hourly or sub-hourly scales, which is critical to understanding mesoscale, short-lived events. Several studies show NWP models still have limitations in simulating extreme precipitation events, especially in complex orography areas. Therefore, a better understanding of such events is fundamental to promoting continuous improvements in operational weather forecasting and contributing to more reliable forecasts of such events in the future.

A framework for reconstructing marine heatwaves from individual foraminifera in sedimentary archives

Marine heatwaves (MHWs) are warm sea surface temperature (SST) anomalies with substantial ecological and economic consequences. Observations of MHWs are based on relatively short instrumental records, which limit the ability to forecast these events on decadal and longer timescales. Paleoclimate reconstructions can extend the observational record and help to evaluate model performance under near future conditions, but paleo-MHW reconstructions have received little attention, primarily because marine sediments lack the temporal resolution to record short-lived events. Individual foraminifera analysis (IFA) of paleotemperature proxies presents an intriguing opportunity to reconstruct past MHW variability if strong relationships exist between SST distributions and MHW metrics. Here, we describe a method to test this idea by systematically evaluating relationships between MHW metrics and SST distributions that mimic IFA data using a 2000-member linear inverse model (LIM) ensemble. Our approach is adaptable and allows users to define MHWs based on multiple duration and intensity thresholds and to model seasonal biases in five different foraminifera species. It also allows uncertainty in MHW reconstructions to be calculated for a given number of IFA measurements. An example application of our method at 12 north Pacific locations suggests that the cumulative intensity of short-duration, low-intensity MHWs is the strongest target for reconstruction, but that the error on reconstructions will rely heavily on sedimentation rate and the number of foraminifera analyzed. This is evident when a robust transfer function is applied to new core-top oxygen isotope data from 37 individual Globigerina bulloides at a site with typical marine sedimentation rates. In this example application, paleo-MHW reconstructions have large uncertainties that hamper comparisons to observational data. However, additional tests demonstrate that our approach has considerable potential to reconstruct past MHW variability at high sedimentation rate sites where hundreds of foraminifera can be analyzed.

Preparedness and Response to Flooding Risks by Kenya Wildlife Service in Hells Gate National Park, Nakuru County, Kenya

Floods are short-lived events that occur abruptly with little to no warning and are among the most dangerous disasters relating to weather due to the hazardous conditions caused for people, the destruction of property and the loss of life as well. Thus, minimizing flooding impacts timely and passing accurate information is critical in flood preparedness and response. Previous studies have focused on the probability of floods occurring and their magnitude, therefore leaving a knowledge gap on preparedness and response to flooding risks in national parks by government agencies in Kenya. Hell’s Gate National Park experiences significant flash flooding; therefore, it provided a good venue to study the levels of preparation and response mechanisms available in Kenyan national parks. The objectives of the study were to understand the level of preparedness and mechanisms to respond to flooding events by Kenya Wildlife Service in Hells Gate National Park. The study was guided by a descriptive research design which involved collecting quantitative and qualitative data from 118 park users and other key informants. The study found that the Kenya Wildlife Service plays a crucial role in flood preparedness and response, but there is room for improvement in early warning systems, hazard map distribution, and user education because only 36.6% of the respondents were aware of escape routes to be used during floods. In terms of recommendations, the study found that it is crucial to enhance the existing flood preparedness and response mechanisms within the park including investing in advanced technology for early warning systems, conducting regular drills, and fostering community engagement and partnerships, continuous improvement of flood preparedness and response plans, along with a robust communication strategy.

Shock persistence, uncertainty, and news-driven business cycles

Abstract This paper distinguishes news about short-lived events from news about changes in longer term prospects using surveys of expectations. Employing a multivariate GARCH-in-Mean model for the US, the paper illustrates how the different types of news influence business cycle dynamics. The influence of transitory output shocks can be relatively large on impact but gradually diminishes over two to three years. Permanent shocks drive the business cycle, generating immediate stock price reactions and gradually building output effects, although they have more immediate output effects during recessions through the uncertainties they create. Markedly different macroeconomic dynamics are found if these explicitly identified types of news or uncertainty feedbacks are omitted from the analysis.

Ocean oxygenation and ecological restructuring caused by the late Paleozoic evolution of land plants

The dramatic increase in ocean-atmosphere oxygen levels during the Devonian and Mississippian is increasingly linked to the diversification of land plants, yet the timing and extent of this event remain uncertain. This study uses the redox-sensitive rare earth element cerium (cerium anomaly—Ce/Ce*) to investigate ocean redox conditions during the deposition of globally distributed Paleozoic carbonate strata. Our Paleozoic Ce/Ce* record suggests that Cambrian, Ordovician, and Silurian oceans had relatively low O2 levels (mean Ce/Ce* = 0.86 ± 0.10, 0.91 ± 0.14, and 0.91 ± 0.10 [±1σ], respectively). In contrast, short-lived ocean oxygenation events, possibly related to the diversification of small land plants, likely occurred throughout the Early and Middle Devonian (mean Ce/Ce* = 0.80 ± 0.07 and 0.58 ± 0.14, respectively). “Modern” Ce/Ce* values (<0.36) first occurred during the Late Devonian, suggesting that the main phase of Devonian and Mississippian oceanic oxygenation was related to the evolution of large vascular plants and the first forests. Despite this, the significant variability of Ce/Ce* values during this time suggests that shallow marine settings were susceptible to redox instability, possibly caused by upwelling of anoxic deep waters. This redox instability potentially provides evidence of a mechanism for contemporaneous mass extinction and metazoan reef collapse events. Development of strongly oxic conditions during the Late Devonian may have resulted in the demise of many Paleozoic-type organisms, facilitated the radiation of the modern evolutionary fauna, and established the modern oxygenated ocean-atmosphere system.

Probabilistic hazard analyses for a small island: methods for quantifying tephra fall hazard and appraising possible impacts on Ascension Island

Proximal to the source, tephra fall can cause severe disruption, and populations of small volcanically active islands can be particularly susceptible. Volcanic hazard assessments draw on data from past events generated from historical observations and the geological record. However, on small volcanic islands, many eruptive deposits are under-represented or missing due to the bulk of tephra being deposited offshore and high erosion rates from weather and landslides. Ascension Island is such an island located in the South Atlantic, with geological evidence of mafic and felsic explosive volcanism. Limited tephra preservation makes it difficult to correlate explosive eruption deposits and constrains the frequency or magnitude of past eruptions. We therefore combined knowledge from the geological record together with eruptions from the analogous São Miguel island, Azores, to probabilistically model a range of possible future explosive eruption scenarios. We simulated felsic events from a single vent in the east of the island, and, as mafic volcanism has largely occurred from monogenetic vents, we accounted for uncertainty in future vent location by using a grid of equally probable source locations within the areas of most recent eruptive activity. We investigated the hazards and some potential impacts of short-lived explosive events where tephra fall deposits could cause significant damage and our results provide probabilities of tephra fall loads from modelled events exceeding threshold values for potential damage. For basaltic events with 6–10 km plume heights, we found a 50% probability that tephra fallout across the west side of the island would impact roads and the airport during a single explosive event, and if roofs cannot be cleared, three modelled explosive phases produced tephra loads that may be sufficient to cause roof collapse (≥ 100 kg m−2). For trachytic events, our results show a 50% probability of loads of 2–12 kg m−2 for a plume height of 6 km increasing to 898–3167 kg m−2 for a plume height of 19 km. Our results can assist in raising awareness of the potential impacts of tephra fall from short-lived explosive events on small islands.

The diurnal variation of dust and water ice aerosol optical depth at Jezero crater observed by MEDA/TIRS over a full Martian year

The Thermal InfraRed Sensor (TIRS) on the Perseverance rover has provided nearly two full Mars years of systematic monitoring of the total aerosol optical depth above Jezero Crater. These observations span a wide range of timescales, capturing seasonal patterns, diurnal variations, and minute-to-minute fluctuations in aerosol loading. By combining TIRS retrievals with orbital observations, the relative contributions of dust and water ice aerosols can be estimated, revealing their different seasonal and diurnal behaviors. The TIRS record shows distinct periods of dust storm activity, including strong regional storms during the perihelion season as well as short-lived but intense dust events outside the typical dust storm season. Water ice clouds exhibit pronounced seasonal and diurnal variability, with peak activity occurring during the aphelion season but with a presence throughout the year. The diurnal variation of clouds differs significantly between the aphelion and perihelion seasons, with clouds persisting throughout the night during the aphelion season, while largely absent outside of specific periods after sunrise and sunset during the perihelion season. These results provide new insights into the complex behavior of aerosols at Jezero Crater and their connections to atmospheric dynamics and the Martian dust and water cycles.

Evaluating background and local contributions and identifying traffic-related pollutant hotspots: insights from Google Air View mobile monitoring in Dublin, Ireland

Mobile monitoring provides high-resolution observation on temporal and spatial scales compared to traditional fixed-site measurement. This study demonstrates the use of high spatio-temporal resolution of air pollution data collected by Google Air View vehicles to identify hotspots and assess compliance with WHO Air Quality Guidelines (AQGs) in Dublin City. The mobile monitoring was conducted during weekdays, typically from 7:00 to 19:00, between 6 May 2021 and 6 May 2022. One-second data were aggregated to 377,113 8 s road segments, and 8 s rolling medians were aggregated to hourly and daily levels for further analysis. We assessed the temporal variability of fine particulate matter (PM2.5), nitrogen monoxide (NO), nitrogen dioxide (NO2), ozone (O3), carbon monoxide (CO), and carbon dioxide (CO2) concentrations at hyperlocal levels. The average daytime median concentrations of NO2 (28.4 ± 15.7 µg/m3) and PM2.5 (7.6 ± 4.7 µg/m3) exceeded the WHO twenty-four hours (24 h) Air Quality Guidelines in 49.4% and 9% of the 1-year sampling time, respectively. For the diurnal variation of measured pollutants, the morning (8:00) and early evening (18:00) showed higher concentrations for NO2 and PM2.5, mostly happening in the winter season, while the afternoon is the least polluted time except for O3. The low-percentile approach along with 1-h and daytime minima method allowed for decomposing pollutant time series into the background and local contributions. Background contributions for NO2 and PM2.5 changed along with the seasonal variation. Local contributions for PM2.5 changed slightly; however, NO2 showed significant diurnal and seasonal variability related to traffic emissions. Short-lived event enhancement (1 min to 1 h) accounts for 36.0–40.6% and 20.8–42.2% of the total concentration for NO2 and PM2.5. The highly polluted days account for 56.3% of total NO2, highlighting local traffic is the dominant contributor to short-term NO2 concentrations. The longer-lived events (> 8 h) enhancement accounts for 25% of the monitored concentrations. Additionally, conducting optimal hotspot analysis enables mapping the spatial distribution of “hot” spots for PM2.5 and NO2 on highly polluted days. Overall, this investigation suggests both background and local emissions contribute to PM2.5 and NO2 pollution in urban areas and emphasize the urgent need for mitigating NO2 from traffic pollution in Dublin.

Preliminary results of the Single Event Effect testing for the ULTRASAT sensors

ULTRASAT (ULtra-violet TRansient Astronomy SATellite) is a wide-angle space telescope that will perform a deep time-resolved all-sky survey in the near-ultraviolet (NUV) spectrum. The science objectives are the detection of counterparts to short-lived transient astronomical events such as gravitational wave sources and supernovae. The mission is led by the Weizmann Institute of Science and is planned for launch in 2026 in collaboration with the Israeli Space Agency and NASA. DESY will provide the UV camera, composed by the detector assembly located in the telescope focal plane and the remote electronics unit. The camera is composed out of four back-metallized CMOS Image Sensors (CIS) manufactured in the 4T, dual gain Tower process. As part of the radiation qualification of the camera, Single Event Effect (SEE) testing has been performed by irradiating the sensor with heavy ions at the RADEF, Jyvaskyla facility. Preliminary results of both Single Event Upset (SEU) and Single Event Latch-up (SEL) occurrence rate in the sensor are presented. Additionally, an in-orbit SEE rate simulation has been performed in order to gain preliminary knowledge about the expected effect of SEE on the mission.

Dry hydroclimates in the late Palaeocene-early Eocene hothouse world

Extreme global warming can produce hydroclimate changes that remain poorly understood for sub-tropical latitudes. Late Palaeocene-early Eocene (LPEE; ~58-52 Ma) proto-Mediterranean zones of the western Tethys offer opportunities to assess hydroclimate responses to massive carbon cycle perturbations. Here, we reconstruct LPEE hydroclimate conditions of these regions and find that carbon cycle perturbations exerted controls on orbitally forced hydroclimate variability. Long-term (~6 Myr) carbon cycle changes induced a gradual precipitation/moisture reduction, which was exacerbated by some short-lived (<200 kyr) carbon cycle perturbations that caused rapid warming and exceptionally dry conditions in western Tethyan continental areas. Hydroclimate recovery following the greatest short-lived global warming events took ~24-27 kyr. These observations support the notion that anthropogenically driven warming can cause widespread aridification with impacts that may last tens of thousands of years.

Changes in the particulate organic carbon pump efficiency since the Last Glacial Maximum in the northwestern Philippine Sea

Changes in bottom and pore water oxygenation over glacial – interglacial cycles have influenced the ocean's capacity to store particulate organic carbon regardless of its source, either the marine primary productivity or the continent-to-ocean transfer of terrestrial organic matter. In the Philippine Sea, east off Taiwan, despite being currently oligotrophic, the enhanced East Asian Winter Monsoon during the Last Glacial Maximum and the Heinrich Stadial 1 might have altered the nutrient budget in surface waters by providing nutrients from the Eurasian loess dust and deepening the vertical mixing, bringing nutrients from the nutrient-enriched Kuroshio Current subsurface waters to the surface. During the deglaciation, previous studies also suggest an overall weakening of the marine biological pump during the Heinrich Stadial 1, and the rise in sea level is expected to have led to a global significant decline in the ability of continents to bury their particulate organic carbon in marine sediments. However, changes in the continent-ocean transfer of terrestrial organic matter and on the marine biological pump around Taiwan remain poorly constrained.In the present study, we have thus aimed to reconstruct bottom – pore water oxygenation, past marine primary productivity and continental-ocean transfer of terrestrial particulate organic carbon to the ocean since the end of the Last Glacial Maximum, in order to better constrain the ability of marine sediments to capture atmospheric carbon over the past 20,000 years. To this end, sediment core MD18-3523 has been recovered from a levee of Hoping Canyon, north-east of Taiwan, in the Ryukyu forearc basin. The reconstructions were made possible by the application of multivariate statistics and transfer functions on benthic foraminiferal assemblages, by the measurement of total organic carbon concentration and by the investigation of chemical element ratios obtained from X-ray fluorescence (XRF).We observed a transition across the Bølling–Allerød and the Younger Dryas from suboxic-dysoxic bottom – pore waters during Heinrich Stadial 1 to oxic-suboxic during the Holocene, and revealed an increase in marine primary productivity during Heinrich Stadial 1 in all probability due to intensified East Asian Winter Monsoon winds. We have also identified periods of enhanced terrestrial particulate organic carbon transfer to the ocean driven by short-lived extreme events, most likely typhoons, during the Bølling–Allerød, at the beginning of the Early Holocene and the end of the Late Holocene, when the typhoon dynamics affecting Taiwan were intensified. Overall, these findings suggest an enhanced marine biological pump during the Heinrich Stadial 1 and an efficient carbon turbidity pump during the Bølling–Allerød, the Early and Late Holocene, contrasting with the western coast of Taiwan.

Characteristics of Marine Heatwaves in the Southeastern Baltic Sea Based on Long-Term In Situ and Satellite Observations

Marine heatwaves (MHWs) are known to pose a threat to aquatic ecosystems and coastal communities and, as a result, they receive significant attention nowadays, thus motivating our scientific interest in better understanding the regional patterns of these events. In this study, we analyze MHWs in the SE part of the Baltic Sea, defining them as anomalously warm water events, where the water temperature exceeds the 90th percentile threshold of the corresponding calendar day for at least five or more consecutive days. Our study is based on a combination of long-term (1993–2023) in situ data, field measurements, and satellite-derived sea surface temperature data during the warm (May–August) period. Study results suggest that although short-lived (5–9 days) MHW events typically dominate throughout the analyzed period, the occurrences of longer (more than three weeks) and more intense MHWs have increased in our study region in the recent decade. The heatwaves are observed both in coastal and open waters, with SST anomalies up to around 5–6 °C above the 90th percentile threshold during extreme events, extending thermal influence as deep as 20 m during prolonged and more intense events. We believe that the results of this study contribute to a better understanding of MHW patterns in the study region, which is important from an ecological and socio-economic point of view, providing valuable insights for human health aspects as well.

Low-redshift absorption in the Seyfert galaxy PG1211+143 – a distant inflow maintaining off-plane accretion or the gravitational redshift of matter orbiting the SMBH?

ABSTRACT The detection of a high-velocity (∼0.3c) inflow of highly ionized matter during an extended XMM–Newton observation of the luminous Seyfert galaxy PG1211+143 in 2014 provided the first direct evidence of a short-lived accretion event, and an explanation for the powerful winds (UFOs) now recognized as a common property of many luminous Seyfert galaxies. Although the ultra-fast inflow observed at a redshift of 0.483 was detected in only one of seven spacecraft orbits, weaker (lower column) but more persistent absorption is seen at a redshift of 0.123 in the high-exposure soft X-ray (RGS) spectra summed over all seven individual spacecraft orbits. Similar stacking of the higher energy (pn camera) spectra reveals underlying absorption at a redshift of 0.148. Interpreted, conventionally, as a Doppler redshift, the RGS observation indicates a line-of-sight inflow velocity v ∼ 0.038c and (free-fall) radial location at 1400 Rg, with the higher redshift and ionization in pn camera spectra perhaps detecting that inflow closer to the black hole. A very different explanation would be absorption in matter subject to the strong gravity close to the SMBH, an interpretation supported by the launch of a new UFO in the final spacecraft orbit.

Centennial-scale cooling-induced megadroughts in Myanmar's tropical arid region over the past 8000 years

The future impact of global warming on tropical arid regions is unclear due to uncertainties about the correlation between rising temperatures and changes in precipitation patterns. A critical factor is the reliability of the sedimentary chronologies. Hence, to better understand the potential long-term consequences of climatic warming or cooling for tropical arid regions we compared a pollen record from the annually-laminated sediments of a crater lake in Myanmar with ice core records of the Siberian High, both of which have an annual resolution. Our findings reveal that over the past 8000 years, the Myanmar region experienced six significant drought events, three of which coincided precisely with intensifications of the Siberian High-pressure system. Furthermore, five out of these six events were synchronous with the North Atlantic Bond events within the limit of the dating uncertainties. Conversely, warm periods were associated with increased precipitation along with relatively short-lived drought events. Our findings suggest that regardless of the El Niño intensity, a cooling trend in the Northern Hemisphere may result in persistent extreme drought conditions in arid tropical regions. Therefore, as well as the environmental implications of global warming, it is also important to address the potential hazards associated with cooling, especially in arid tropical regions. To facilitate effective disaster management and to develop strategies for climate change mitigation, it is crucial to better understand the complex relationship between temperature fluctuations and drought. Overall, our findings are a reminder of the importance of not ignoring the potential disasters that may arise from cooling trends while focusing exclusively on warming.

Comparisons between Short- and Long-Lived Cross-Equatorial Flow Events over the Maritime Continent: Perspective from the Intraseasonal Oscillation

Abstract The duration of cross-equatorial flow (CEF) events over the Maritime Continent (MC) varies greatly, from 3 days to more than 1 month. In this study, we classify CEF events into short- and long-lived ones using a threshold of 7 days, and conduct separate investigations on their statistical and evolution characteristics, as well as the associated physical processes from the perspective of two dominant modes of the intraseasonal oscillation. Results indicate that short-lived events, characterized by westward-propagation southerly anomalies, are largely dependent on the 10–25-day oscillation, while the contribution of the 30–60-day component is negligible. The associated enhanced convection is primarily confined to the western North Pacific (WNP) and moves northwestward, accompanied by an anomalous cyclone. In contrast, long-lived events show consistent changes among different CEF branches, characterized by southerly anomalies dominating the MC, which benefit from the favorable background of the 30–60-day oscillation. Associated convection anomalies show a dipole pattern, with enhanced convection over WNP and suppressed convection over the Indian Ocean. The enhanced WNP convection gradually migrates northward, inducing CEF anomalies via a continuous anomalous cyclone, while the suppressed convection can be found to slightly expand to the MC. Meanwhile, the 10–25-day oscillation shows similar magnitude and evolution with that in short-lived events, but is no longer crucial to the establishment of long-lived events.

History of Ceres’s Cold Traps Based on Refined Shape Models

Permanently shadowed regions (PSRs) in the north polar region of Ceres have been previously mapped by the Dawn spacecraft. Putative ice deposits are found in some of these PSRs, whereas most PSRs host no bright deposits, which is thought to be due to oscillations of the axis tilt with a ∼25 ka period. We use stereophotoclinometry to construct refined topographic models of PSR-hosting craters. Ray-tracing calculations reveal that no PSRs remain at the maximum axis tilt, which implies that the ice deposits are remarkably young. The bright ice deposits do not extend beyond PSRs at an axis tilt of 10°, which last occurred about 6 ka ago. This suggests that water is delivered to the polar regions or exposed within the craters by frequent and short-lived events. Surface temperatures are calculated with a terrain irradiance model to delineate cold traps. Based on maximum equilibrium temperatures, Cerean PSRs are too warm to trap supervolatiles.

TESS Photometry of AM Her and AR UMa: Binary Parameters, Cyclotron Emission Modeling, and Mass Transfer Duty Cycles

Transiting Exoplanet Survey Satellite (TESS) photometry of the polars AM Herculis (AM Her) and AR Ursae Majoris (AR UMa) is presented, along with high-speed photometry. AM Her shows a variety of high states with frequent transitions between them. TESS photometry of AR UMa in the low state reveals no evidence of accretion, while the McDonald 2.1 m telescope caught AR UMa in its high accretion state. Roche-lobe overflow is shut off during low states of AR UMa, while accretion often still takes place during low states of AM Her. We derive inclinations of 50° and 70° for AM Her and AR UMa respectively. To model the high-state light curves of AM Her, we employ a self-organized map light-curve classification scheme to establish common accretion configurations. The cyclotron radiation properties then allow the production of emission region maps on the surface of the white dwarf. The accretion geometry of AM Her is most consistent with a multipolar field structure. The high-state photometry of AR UMa has stochastic accretion flaring, which we attribute to magnetically buffeted mass transfer through the inner Lagrangian point L1. To consider this possibility, we examine the magnetism of both stars and argue that the local magnetic field near L1 can initiate short-lived accretion events and affect transitions between high and low accretion states in both AM Her and AR UMa. In particular, AR UMa has the low state as its default, while AM Her and most other active polars are in the high state by default.