Dusk Time Research Articles

GIGANTEA adjusts the response to shade at dusk by directly impinging on PHYTOCHROME INTERACTING FACTOR 7 function

For plants adapted to bright light, a decrease in the amount of light received can be detrimental to their growth and survival. Consequently, in response to shade from surrounding vegetation, they initiate a suite of molecular and morphological changes known as the shade avoidance response through which stems and petioles elongate in search for light. Under sunlight-night cycles, the plant's responsiveness to shade varies across the day, being maximal at dusk time. While a role for the circadian clock in this regulation has long been proposed, mechanistic understanding of how it is achieved is incomplete. Here, we show that the clock component GIGANTEA (GI) directly interacts with the transcriptional regulator PHYTOCHROME INTERACTING FACTOR 7 (PIF7), a key player in the response to shade. GI represses PIF7 transcriptional activity and the expression of its target genes in response to shade, thereby fine-tuning the magnitude of the response to limiting light conditions. We find that under light/dark cycles, this function of GI is required to adequately modulate the gating of the response to shade at dusk. Importantly, we also show that this circuit primarily operates in epidermal cells, highlighting the relevance of tissue-specific clock-output connections for the regulation of plant development in resonance with the environment.

Triple Ionosophere PhotoMeter onboard Fengyun-3E satellite: Data validation and ionosphere information extraction

The Triple Ionosophere PhotoMeter (TRIPM) is designed to make the disk observations of the Earth airglow emissions at OI 135.6 nm and N2 Lyman-Birge-Hopfield (LBH) band that flew aboard the newly launched early morning satellite Fengyun-3E (FY-3E) which was launched on July 5th, 2021. This is the first attempt to obtain the global twilight airglow data in the far ultraviolet band using Ionosophere PhotoMeter. The seasonal behavior of the twilight airglow at the OI 135.6 nm and N2LBH band is exhibited and interpreted in the paper. Validity of the TRIPM data is analyzed by comparison with the simulation results of the Global Airglow (GLOW) and the simulation results reveal good consistency with the observational results. Furthermore, based on the ionospheric contributions calculated by GLOW model, we extract the ionospheric information from the TRIPM 135.6 nm emissions. This means the ionospheric signature in the 135.6 nm radiance at the dawn and dusk times can be provided. Comparison between the ionospheric 135.6 nm radiance due to O+ and electron radiative recombination with GPS TEC data shows a similar morphology of equatorial arcs and seasonal variation of the ionosphere.

Morphology of equatorial F-region irregularities over the Indian longitude sector using GPS-derived ROTI observations

The occurrence characteristics of Equatorial F-region Irregularities (EFIs) along the Indian longitude sector are investigated using GPS-derived ROTI observations from 2010 to 2023, under both quiet and disturbed geomagnetic conditions. The analysis of the results emphasizes a strong dependence of EFIs occurrence on solar cycle variation. Additionally, the EFIs are more intense at the EIA regions under maximum solar activity periods attributed to the high ambient electron density in the F-layer. The occurrence of EFIs is found to be severe and frequently observed in equinox seasons in contrast to solstice seasons. Also, the occurrence of EFIs exhibits equinoctial asymmetry with more intense EFIs in the spring equinox than autumn equinox during the peak and declining periods of the solar cycle. Conversely, severe EFIs are observed during autumn equinox than spring equinox in the ascending phase of the solar cycle. The seasonal occurrence probability of EFIs is highest in the equinox seasons, following the winter solstice, and summer solstice in high solar activity conditions. Investigations of EFIs during two prominent geomagnetic storm events (17 March 2015 and 08 September 2017) during the study period show that the storm-induced Prompt Penetration Electric Fields (PPEFs) modulated the regular intensity of dusk time Pre-Reversal Enhancement (PRE), resulting in poleward expansion of ionospheric irregularities up to mid-latitude regions with spatial time lag. However, storm-induced westward electric fields and oscillating IMF Bz created Counter Electrojet (CEJ) like conditions, suppressing the dusk time ionospheric irregularities over dip equatorial and low-latitude regions on 17 March 2013. This study provides a comprehensive understanding of how ionospheric irregularities manifest under varying conditions, thereby supporting further research on substantiating the spatiotemporal EFIs characteristics and their predictions over the region.

CstMYB1R1, a REVEILLE-8-like transcription factor, regulates diurnal clock-specific anthocyanin biosynthesis and response to abiotic stress in Crocus sativus L.

CstMYB1R1 acts as a positive regulator of Crocus anthocyanin biosynthesis and abiotic stress tolerance which was experimentally demonstrated through molecular analysis and over-expression studies in Crocus and Nicotiana. Regulatory mechanics of flavonoid/anthocyanin biosynthesis in Crocus floral tissues along the diurnal clock has not been studied to date. MYB proteins represent the most dominant, functionally diverse and versatile type of plant transcription factors which regulate key metabolic and physiological processes in planta. Transcriptome analysis revealed that MYB family is the most dominant transcription factor family in C. sativus. Considering this, a MYB-related REVEILLE-8 type transcription factor, CstMYB1R1, was explored for its possible role in regulating Crocus flavonoid and anthocyanin biosynthetic pathway. CstMYB1R1 was highly expressed in Crocus floral tissues, particularly tepals and its expression was shown to peak at dawn and dusk time points. Anthocyanin accumulation also peaked at dawn and dusk and was minimum at night. Moreover, the diurnal expression pattern of CstMYB1R1 was shown to highly correlate with Crocus ANS/LDOX gene expression among the late anthocyanin pathway genes. CstMYB1R1 was shown to be nuclear localized and transcriptionally active. CstMYB1R1 over-expression in Crocus tepals enhanced anthocyanin levels and upregulated transcripts of Crocus flavonoid and anthocyanin biosynthetic pathway genes. Yeast one hybrid (Y1H) and GUS reporter assay confirmed that CstMYB1R1 interacts with the promoter of Crocus LDOX gene to directly regulate its transcription. In addition, the expression of CstMYB1R1 in Nicotiana plants significantly enhanced flavonoid and anthocyanin levels and improved their abiotic stress tolerance. The present study, thus, confirmed positive role of CstMYB1R1 in regulating Crocus anthocyanin biosynthetic pathway in a diurnal clock-specific fashion together with its involvement in the regulation of abiotic stress response.

Estimation of dusk time F-region electron density vertical profiles using LSTM neural networks: A preliminary investigation

The vertical profile of the ionosphere density plays a significant role in the development of low-latitude Equatorial Plasma Bubbles (EPBs), that in turn lead to ionospheric scintillation which can severely degrade precision and availability of critical users of the Global Navigation Satellite System (GNSS). Accurate estimation of ionospheric delays through vertical electron density profiles is vital for mitigating GNSS errors and enhancing location-based services. The objective of this study is to propose a neural network, trained with radio occultation data from the COSMIC-1 mission, that generates average ionospheric electron density profiles during dusk, focusing on the pre-reversal enhancement of the zonal electric field. Results show that the estimated profiles exhibit a clear seasonal pattern, and reproduce adequately the climatological behavior of the ionosphere, thus presenting strong appeal on ionospheric error attenuation.

Geographic variability in the seasonality of euphausiid diel vertical migrations among three locations in coastal British Columbia, Canada

Abstract Diel vertical migration (DVM) is a behaviour observed across zooplankton taxa in marine and limnetic systems worldwide. DVM influences biogeochemical cycling and carbon drawdown in oceanic systems and alters prey availability for zooplanktivorous species. DVM has been well studied among zooplankton, and many exogenous and endogenous triggers as well as adaptive significances have been hypothesized. However, second-order variability in DVM timing, the deviation of DVM times to respective dawn and dusk times throughout the year, is a less-studied phenomenon that can help identify the factors influencing migration timing as well as demonstrate the changes of DVM behaviours within and across systems. Here, we quantified seasonal trends in second-order variability of DVM timing of euphausiids at Brooks Peninsula, Clayoquot Canyon, and Saanich Inlet near Vancouver Island, British Columbia, Canada, over multiple years using upward-facing moored echosounders. We used generalized additive mixed models to characterize this seasonality. DVM timing relative to civil twilight times showed strong seasonality at all locations, with euphausiids remaining near the surface longer than expected in spring and summer, and shorter than expected in winter. Euphausiids spent less time near the surface at Brooks Peninsula and Clayoquot Canyon than at Saanich Inlet throughout the year. Increased primary productivity in Saanich Inlet, which reduced light penetration and hid euphausiids from visual predators, likely drove this difference. Our findings confirm that proper understanding of DVM behaviours must account for seasonal variability due to context-specific oceanographic and ecological parameters. This is particularly pertinent when attempting to model the biogeochemical or predator–prey interactions influenced by DVM behaviours.

Standardisation of Units for Assessment of Adult Disease Vector Density under Vector Control Programmes in India

Vector density is one of the most frequently used monitoring parameters of entomological surveillance under any vector control programme. Vector control applications are guided by the density of vectors or their abundance in different seasons and settings. The vectors of different common vector-borne diseases viz. malaria, filaria, kala-azar, dengue, chikungunya, Zika and Japanese Encephalitis (JE) have different bionomics. Scientists, researchers, and public health entomologists of various research institutes and programmes are engaged in studying vector bionomics through vector surveillance activities. The most common parameter used to estimate the density of vector and non-vector species of both mosquitoes and flies is the collection of species in a given unit of time. In the malaria control programme, it started as a collection of resting vector mosquitoes at a specified time of dawn and dusk. These are expressed in a number of forms viz. ‘per man hour’, ‘per ten man hour’ and ‘ten man hour’ to ascertain the level of vector population and its increasing or decreasing trend with climatic factors which may be correlated with the active transmission of the disease. The minimum level of density at which active transmission was evidenced has been termed as ‘critical density’. Various vector species have different critical densities. Many other parameters are used to estimate vector or non-vector populations but such different units may often lead to confusion among the field functionaries. This article describes the significance of ‘per man-hour density’, the methodology which has been in practice for ages and the statistical method for its calculation. To avoid misconception, it should be understood that the density expressed for a particular species is the ‘differential density’ and not the absolute density.

A Statistical Analysis of Plasma Bubbles Observed by Swarm Constellation during Different Types of Geomagnetic Storms

Based on the observations of Ionospheric Bubble Index (IBI) data from the Swarm mission, the characteristics of plasma bubbles are investigated during different types of geomagnetic storms recorded from 2014 to 2020. The geometrical constellation of the Swarm mission enabled us to investigate the altitudinal profile of the IBIs during different activity levels in a statistical mean. Results show that the majority of IBIs associated with moderate storms are observed at low altitudes and the probability of observing IBIs at high altitudes (Swarm-B) increases with the increase in storm level. This is confirmed by observing the F2 layer peak height (hmF2) during super storm events at larger altitudes using COSMIC data. The maximum number of IBIs is recorded within the South Atlantic Anomaly (SAA) region with a long duration time and tends to increase only during dusk time. Both the large duration time and number of IBIs over the South Atlantic Anomaly (SAA) suggest that the gradient in the electron density and the depression in the magnetic field are the main factors controlling IBI events. Also, the IBIs at high altitudes are larger at sunset and at low altitudes pre-midnight. In addition, the occurrence of IBIs is always larger in the northern hemisphere than in the southern hemisphere irrespective of the type of storm, as well as during the summer months. Moreover, there is no correlation between the duration time of IBIs and both the altitudinal observation of the IBIs and the storm type. Seasonal occurrence of IBIs is larger during equinoxes and vice versa during solstices irrespective of both the type of storm and the altitude of the satellite. The large number of IBIs during equinoxes agrees with the previous studies, which expect that the large electron density is a developer of steeper ∇n. Large occurrences of super storm IBIs observed within the pre-midnight during summer and at sunset during equinoxes are a novel observation that needs further investigation. Also, the majority of IBIs are observed a few hours after geomagnetic substorms, which reflects the role of the Disturbance Dynamo Electric Field (DDEF) as a main driver of IBIs.

Purpose of Crested Francolin Ortygornis sephaena male collective calls at dusk based on livestream audio censusing

The study of diel and seasonal variation in vocal interactions of Crested Francolin Ortygornis sephaena territorial males helps clarify its purpose, thus delivering insights into the behavioural ecology of this species. The goals of the present paper are to describe the vocal footprint of neighbouring Crested Francolin territorial males and understand the purpose of collective calls. We logged remotely into a HD webcam with microphone located in Tembe Elephant National Park (KwaZulu-Natal, South Africa) to listen to male vocal exchanges from August 2018 to November 2019. Territorial call exchanges among three neighbouring males at dusk took place at the onset of, but not during, the breeding season and then again during the non-breeding season. In the latter case vocalisations were emitted even beyond dusk time. Call duration and intensity (calls per minute) did not increase at the onset of the breeding season. Males exchanged calls in a leader-follower manner seemingly unrelated to female attraction and guarding. On the contrary, this cordial collective calling is likely a form of cooperation to detect vocal responses by interlopers.

Brief light exposure at dawn and dusk can encode day-length in the neuronal network of the mammalian circadian pacemaker.

The central circadian pacemaker in mammals, the suprachiasmatic nucleus (SCN), is important for daily as well as seasonal rhythms. The SCN encodes seasonal changes in day length by adjusting phase distribution among oscillating neurons thereby shaping the output signal used for adaptation of physiology and behavior. It is well-established that brief light exposure at the beginning and end of the day, also referred to as "skeleton" light pulses, are sufficient to evoke the seasonal behavioral phenotype. However, the effect of skeleton light exposure on SCN network reorganization remains unknown. Therefore, we exposed mice to brief morning and evening light pulses that mark the time of dawn and dusk in a short winter- or a long summer day. Single-cell PER2::LUC recordings, electrophysiological recordings of SCN activity, and measurements of GABA response polarity revealed that skeleton light-regimes affected the SCN network to the same degree as full photoperiod. These results indicate the powerful, yet potentially harmful effects of even relatively short light exposures during the evening or night for nocturnal animals.

STRUCTURAL DAKWAH STRATEGY OF THE LOCAL GOVERNMENT OF SAMBAS POST CONFLICT OF SAMBAS ETHNICITY IN WEST KALIMANTAN

This writing specifically ellaborates the structural dakwah strategy of the Sambas Local Government post conflict. This is a qualitative-based research with sociological and communication approach. The data source of this research comes from the Ministry of Religions, Local Government, Religious Harmony Forum (FKUB), Indonesian Council of Ullemas (MUI) Sambas Regency, Sambas Muslim Forum TQN, religious and public figures in Sambas. Also, people who presumably can give information related to this topic. All data is collected through observation, interviews, and documentation. Data is analyzed through 4 stages of processess; data reduction, data presentation, data verification and conclusion. Fact-check process is using triangulation, reference books, and applying member check. The result of this research shows that the structural dakwah strategy, in which the local government FKUB, and MUI are in charge of, is performing the strategy throughout several religious prorgram. It is aligned with the regent of Sambas vision that has been determined in RPJMD 2016-2021 (the government masterplan). For example, building the life quality of religious community, providing hajj service facilites, providing religious consultancy, empowering houses of Quran in the districts, conducting preach during Ramadan, reciting on Magrib (dusk time), and visiting people’s house programme. There are also another program such as young preachers recruitment, non-civil servant consultant, and empowering people and religious teachers to preserve the community post conflict in the places where the social religious problems threaten the community.

SEA FOG DETECTION BASED ON DYNAMIC THRESHOLD ALGORITHM AT DAWN AND DUSK TIME

Abstract. Dawn and dusk time is the high frequency period of sea fog occurrence, which is very important for all-day sea fog remote sensing detection. Most polar orbit satellites are limited by time resolution and transit time, and can not detect sea fog at dawn and dusk. Based on the Himawari-8 geostationary satellite data and the analysis of the spectral characteristics of sea fog at dawn and dusk, this paper determines the variation law of the reflectivity and brightness temperature of sea fog at dawn and dusk, chooses sensitive bands, sets the detection index of sea fog and its corresponding dynamic threshold, and realizes the detection of sea fog at dawn and dusk. The case study results indicate that our dynamic threshold algorithm can effectively detect the sea fog at dawn and dusk.

Long Integral Time Continuous Panorama Scanning Imaging Based on Bilateral Control with Image Motion Compensation

Urban remote sensing with moving carriers enables comprehensive monitoring of an urban area. High spatial resolution and wide covering are always required to improve the performance and efficiency of remote sensing. Continuous scanning imaging is a feasible solution. However, imaging motion degrades the performance of a remote sensing system. Rotating motion leads to the loss of key urban morphology information of a panorama imaging. Image translation results in blurry images. For high spatial resolution and high efficiency imaging with low illumination condition, such as imaging at dusk, long-focus lens and long integral time must be further utilized, which makes the problem more severe. In this paper, a novel image motion compensation method is proposed to compensate for image rotation and image translation simultaneously. A quantitative description of image motion, including both image rotation and image translation, is first developed based on the principle of geometrical optics and then analyzed in detail through numerical simulations. Furthermore, a comprehensive image rotation compensation method is developed based on four-channel bilateral control with sliding mode controller, at the same time image translation compensation is performed according to the quantitative relationship of the motion of the scan mirror and image translation compensator. The experimental results show that the proposed method provides effective compensation for image rotation and image translation. This enables acquisition of high spatial resolution urban panoramic images.

Mid and low-latitudinal ionospheric field-aligned currents derived from the Swarm satellite constellation and their variations with local time, longitude, and season

We use the Field Aligned Currents (FAC) data of the 10 quietest days of each month of 2014–2018, the first four years of FAC observational data, derived from Swarm A and C satellites observations to study their characteristics within 15–55° latitude in the northern and −15° to −55° latitude in the southern hemispheres. Results show that in summer months, the noon time FAC have the largest variations. Over the same sector region and the same local time, the FAC have the same trend irrespective of season.Examinations of seasonal patterns indicate that, both dawn and dusk times FACs in both hemispheres always have negative (southbound) variations during summer months. In winter months the dusk time FAC becomes positive only in the southern hemisphere, while the dawn time FAC is ambiguous as it becomes negative only at low latitudes. The noon time FAC is strongly positive (northbound), in both hemispheres in summer months, but during winter months it becomes southbound at mid-latitudes and remains northbound at low latitudes. Over the African, Asian and American sectors, the summer months FAC have identical structure, while in winter months the direction of the dawn and noon times FACs are ambiguous.At the foci points of the solar quiet (SQ) current, the northern hemispheric FAC has the same variation as those observed by Park et al. (2011) and Luhr et al. (2015) during summer months, while during winter months the noon time FAC is still weakly positive. The latitudinal variation of the FAC with respect to longitudes shows that the southern hemispheric FAC at mid-latitudes is always negative at eastern longitudes irrespective of season. It suggests that the FAC is longitudinally dependent.Unlike previous ground based studies, the satellite data not only shows a single prominent negative (southbound) FAC over the African sector region around equinoxes, but it shows that during the March equinox the dusk time FAC is always negative in both hemispheres except at western longitudes 45°, where it has positive patterns. In the middle of summer and winter (months 7 and 1), the noon time FAC varies from positive in summer to negative in winter and the dawn time FAC varies from negative in summer to positive in winter which agrees with the theoretical prediction. The dusk time FAC in the northern hemisphere remains negative which agrees the observations of Park et al. (2011) and Luhr et al. (2015), while in the southern hemisphere it changes from negative in summer to positive in winter.

RISK ASSESSMENT OF ZOONOTIC CUTANEOUS LEISHMANIASIS CASES AMONG MANUAL WORKERS IN EGYPT

The Egyptian endemic foci of cutaneous leishmamasis were mainly in the Sinai Peninsula. To study the epidemiological characteristics of zoonotic cutaneous leishmaniasis cases in special groups in endemic area in Sinai, a descriptive study was conducted to assess the risk of cutaneous leishmania within spreading places in Sinai among special groups working in endemic areas, during the study period from January- December 2015. All patients in the study setting described before were submitted to clinical examination and history taking based on epidemiologically linked diagnosis. Their total number was (124) cases divided into (85) patients locally treated and (39) patients referred to central hospital. The results showed that (85.5%) was in middle education class, had stable work (87%) and working in manual services (91.1). A total of 58.1% slept outdoor at the dusk time (54%). Three quarters (75.8%) didn't use insect repellant and 56.55 didn't use bed nets. Sandy ground, mountain and desert surrounds geographic environment (100%, 97.6% & 96%) respectively. They lived in one floor buildings (85%), dormitories habitat (98%), soiled (92%), have cracks on the wall (60%), ceiling made of wood (74%) and fence was not available in majority of buildings (96.8%). Disfiguring was commonest complain in 55% of cases. The lesions (85%) were ulcers (2x2cm in size (51%), at lower limb (55%) and two in numbers in (50%). All cases were treated with fluconazole and 8.9% was cured. Stibogluconate was given to 91% andwith cure rate of 53%. Both Cryotherapy and laser therapy was applied to 16% of cases. Treatment cured 87% but 39.5% suffered scar complications with main sequelae (15.3%).

RISK ASSESSMENT OF ZOONOTIC CUTANEOUS LEISHMANIASIS CASES AMONG MANUAL WORKERS IN EGYPT

The Egyptian endemic foci of cutaneous leishmamasis were mainly in the Sinai Peninsula. To study the epidemiological characteristics of zoonotic cutaneous leishmaniasis cases in special groups in endemic area in Sinai, a descriptive study was conducted to assess the risk of cutaneous leishmania within spreading places in Sinai among special groups working in endemic areas, during the study period from January- December 2015. All patients in the study setting described before were submitted to clinical examination and history taking based on epidemiologically linked diagnosis. Their total number was (124) cases divided into (85) patients locally treated and (39) patients referred to central hospital. The results showed that (85.5%) was in middle education class, had stable work (87%) and working in manual services (91.1). A total of 58.1% slept outdoor at the dusk time (54%). Three quarters (75.8%) didn't use insect repellant and 56.55 didn't use bed nets. Sandy ground, mountain and desert surrounds geographic environment (100%, 97.6% & 96%) respectively. They lived in one floor buildings (85%), dormitories habitat (98%), soiled (92%), have cracks on the wall (60%), ceiling made of wood (74%) and fence was not available in majority of buildings (96.8%). Disfiguring was commonest complain in 55% of cases. The lesions (85%) were ulcers (2x2cm in size (51%), at lower limb (55%) and two in numbers in (50%). All cases were treated with fluconazole and 8.9% was cured. Stibogluconate was given to 91% andwith cure rate of 53%. Both Cryotherapy and laser therapy was applied to 16% of cases. Treatment cured 87% but 39.5% suffered scar complications with main sequelae (15.3%).

Abstract 272: Circadian disruption and cancer risk in the United States

Abstract Circadian disruption is a probable human carcinogen. Dawn and dusk times occur latter in western compared to eastern regions of each time zone, producing discrepancies between individuals’ biological clock and social time which may lead to circadian disruption and increased risk of cancer. We examined associations between longitude distance from the time zone meridian and age-standardized county-specific cancer incidence rates for total and 23 specific cancers by gender. Four million whites were diagnosed with cancer during 2000-2012 in the Surveillance, Epidemiology and End Results Program in residents of 607 counties in 11 continental US states. The models were adjusted for latitude, poverty, smoking, and state as well as rural/urban location, obesity, and Hispanic composition. The total cancer incidence rates for counties located in the western regions of time zones were significantly elevated for both men and women after Bonferroni correction. The rate ratio (RR) per five degrees of longitude toward the west (corresponding to 20 minutes delay of sunrise) was 1.03 (95% confidence intervals, CI, 1.02-1.04, p=2.7×10-6) for men and 1.04 (95% CI, 1.03-1.05, p=3.8 ×10-10) for women. Chronic lymphocytic leukemia rates for counties in the western portions of time zones were significantly elevated for both men (RR=1.13, 95% CI=1.08-1.20, p=3.1 x10-6) and women (RR=1.12, 95%CI=1.05-1.19, p=3.7 x10-4). Among men, western location within a time zone was associated with elevated risk of prostate cancer (RR=1.04, 95% CI=1.02-1.07, p=4.8 x 10-4). Among women, western location within a time zone was associated with an increase in breast cancer (RR=1.04, 95% CI=1.02-1.06, p=6.5 x 10-5) and corpus uteri cancer (RR=1.10, 95% CI=1.07-1.14, p=2.4 x 10-9 among others. The increased cancer risk with western residency within a time zone is in accord with the circadian disruption hypothesis. Our findings suggest that circadian disruption is not a rare phenomenon affecting only shift workers or international travelers but may be widespread in the general population which has broader implications for public health than generally appreciated. Citation Format: Neil E. Caporaso, Fangyi Gu, Shangda Xu, Susan S. Devesa, Fanni Zhang, Elizabeth B. Klerman, Barry Graubard. Circadian disruption and cancer risk in the United States [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 272. doi:10.1158/1538-7445.AM2017-272

Individuality in northern lapwing migration and its link to timing of breeding

We tracked eight adult northern lapwings Vanellus vanellus (six females and two males) from a Dutch breeding colony by light-level geolocation year-round, three of them for multiple years. We show that birds breeding virtually next to each other may choose widely separated wintering grounds, stretching from nearby the colony west towards the UK and Ireland, and southwest through France into Iberia and Morocco. However, individual lapwings appeared relatively faithful to a chosen wintering area, and timing of outward and homeward migration can be highly consistent between years. Movements of migratory individuals were usually direct and fast, with some birds covering distances of approximately 2000 km within 2 to 4 days of travel. The two males wintered closest and returned earliest to the breeding colony. The female lapwings returned well before the onset of breeding, spending a pre-laying period of 19 to 54 days in the wider breeding area. Despite the potential for high migration speeds, the duration that birds were absent from the breeding area increased with distance to wintering areas, a pattern which was mainly driven by an earlier outward migration of birds heading for more distant wintering grounds. Moreover, females that overwintered closer to colony bred earlier. A large variation in migration strategies found even within a single breeding colony has likely supported the species’ responsiveness to recent climate change as evidenced by a shortened migration distance and an advanced timing of reproduction in Dutch lapwings since the middle of the 20th century. Migration strategies may vary between species, populations, individuals and between years within an individual. Individuals from a particular breeding population may migrate to the same wintering area or they may spread out over much of the non-breeding range. These connections between breeding and non-breeding areas of a migratory species are called ‘migratory connectivity’, and the strength of migratory connectivity has implications for the species ecology, evolution and conservation (Webster et al. 2002). Furthermore, the choice of a certain wintering area and migratory strategy may affect annual schedules including timing of events at breeding area (Marra et al. 1998), which demonstrates the importance to follow individuals throughout the annual cycle. Knowledge of variation in migratory routines within and between individuals of a population is also important to understanding and predicting the ability of species responses to environmental change, including climate change (Conklin et al. 2013). We employed GLS (Global Location Sensing, also called ‘light-level geolocation’ or just ‘geolocation’) technique based on the analysis of diurnal changes in light levels to track annual movements of northern lapwings (Vanellus vanellus; here synonymously termed ‘lapwing(s)’). Archival tags (‘geolocators’) record light intensities to determine dusk and dawn times from which geographical positions (two fixes daily) are calculated; day (night) length determines the latitude and time of local midday (midnight) the longitude (Hill ). Lapwings have been intensively ringed in many European countries for many years. Imboden (1974) undertook an extensive analysis (nicely summarized in Alerstam ) of ring recoveries collected during 1900 to 1969 from birds ringed as unfledged young and recovered within their first year of life or later. Albeit relying mainly on dead recoveries of hunted individuals, this analysis enabled the reconstruction of average seasonal movement patterns at population(s) level. It also revealed a large overlap in non-breeding locations used by lapwings originating from widely separated breeding colonies. Here, we present results from a first-time tracking study on this species by charting the year-round whereabouts of adult lapwings from a Dutch breeding colony. Some individuals were tracked for multiple years thereby providing first insights into individual consistency of migratory timing and choice of non-breeding locations. Finally, we investigate if spatial variation in non-breeding location relates to temporal variation of events at breeding area.

SBAS-derived TEC maps: a new tool to forecast the spatial maps of maximum probable scintillation index over India

With the increase in the use of satellite-based navigation services, the forecasting of L band scintillation has turned out to be of paramount importance as it affects their accuracy and availability. Forecasting the time of occurrence or non-occurrence, strength and probable location of scintillation enables the service providers and users to take appropriate action to mitigate the effects and optimize the services. We use the recently developed method to retrieve TEC from the ionospheric correction data transmitted by the Indian satellite-based augmentation system (SBAS)–GAGAN. By making use of the established linear relation between the dusk time TEC and the maximum probable scintillation intensity (S4max), scintillation forecast maps have been generated as early as 1930 LT. The superposition of actual S4 measurements, obtained from the GAGAN network of receivers, on the forecasted S4max map shows that the actual measurements are less than the predicted S4max except on very few occasions. The potential of the simple technique to predict the 2 D maps of maximum probable scintillation index for the whole night has been demonstrated which with more refinements could evolve into a viable forecast or forewarning system.

Toroidal quarter waves in the Earth’s magnetosphere: observational perspective

Quarter waves in the Earth’s magnetosphere are standing Alfven waves excited on geomagnetic field lines when the conjugate ionospheres display strong asymmetry in conductivity. In this paper, we have examined the characteristics of these waves by analyzing two years (2007–2008) of magnetometer data from the geostationary satellite GOES-11. These waves are predominantly identified during quiet geomagnetic conditions based on interhemispheric conductivity contrast and opposite signs of wave reflection coefficients at the conjugate ionospheres. The observed frequencies are used in a numerical model to compute the equatorial ion density by assuming that the plasma consists only of protons at geostationary height during quiet conditions. The number density of protons thus obtained is compared with an empirical model. The phase difference between the waves observed at the satellite and northern conjugate ground station is in accord with model expectations for quarter mode waves. We also for the first time report the occurrence of an event depicting harmonically structured quarter wave oscillations. Statistical analysis of the seasonal and MLT (Magnetic local time) dependence of these oscillations shows that they mostly occur during solstices and around terminators (i.e. dawn and dusk time). In addition, it is observed that occurrence is more prevalent during dawn in the June solstice and dusk during the December solstice.