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The Large Area Telescope (LAT) onboard the Fermi gamma-ray observatory continuously scans the sky in an energy range from 50 MeV to 1 TeV. The telescope has identified over 6000 gamma-ray emitting sources, approximately half of which are classified as active galactic nuclei (AGN). However, not all of these gamma-ray sources have known redshift values for the reason that redshift estimation following traditional methods can be an expensive, challenging task. Alternatively, as an effort to robustly predict the AGN redshift values, many researchers have recently turned to machine learning methods. However, while the focus has primarily been on predicting specific values, real-world data often allows us only to predict conditional probability distributions, constrained by conditional entropy [ H (Y | X)]. In our study, we employ the Hierarchical Correlation Reconstruction approach to inexpensively predict complex conditional probability distributions, including multimodal ones. This is achieved through independent Mean Squared Error estimation of multiple moment-like parameters, combined into reconstruction of the conditional distribution. By employing linear regression for this purpose, we can develop interpretable models where coefficients describe the contributions of features to conditional moments. This article extends the original approach by incorporating Canonical Correlation Analysis for feature optimization and l1 'lasso' regularization. Our primary focus is on the practical problem of predicting the redshift of AGN using data from the Fourth Fermi -LAT Data Release 3 (4LAC-DR3) data set. [ABSTRACT FROM AUTHOR]

Machine learning has emerged as a powerful tool in the field of gamma-ray astrophysics. The algorithms can distinguish between different source types, such as blazars and pulsars, and help uncover new insights into the high-energy universe. The Large Area Telescope onboard the Fermi gamma-ray telescope has significantly advanced our understanding of the Universe. The instrument has detected a large number of gamma-ray-emitting sources, among which a significant number of objects have been identified as active galactic nuclei. The sample is primarily composed of blazars; however, more than one-third of these sources are either of an unknown class or lack a definite association with a low-energy counterpart. In this work, we employ multiple machine learning algorithms to classify the sources based on their other physical properties. In particular, we utilized smart initialization techniques and self-supervised learning for classifying blazars into BL Lacertae (BL Lac, also BLL) objects and flat-spectrum radio quasars (FSRQs). The core advantage of the algorithm is its simplicity, usage of minimum number of features and easy deployment due to lesser number of parameters without compromising on the performance along with increase in inference speed (at least seven times more than existing algorithms). As a result, the best-performing model is deployed on multiple platforms so that any user irrespective of their coding background can use the tool. The model predicts that out of the 1115 sources of uncertain type in the 4FGL-DR3 catalogue, 820 can be classified as BL Lacs and 295 can be classified as FSRQs. [ABSTRACT FROM AUTHOR]

With the advancement of technology, machine learning-based analytical methods have pervaded nearly every discipline in modern studies. Particularly, a number of methods have been employed to estimate the redshift of gamma-ray loud active galactic nuclei (AGN), which are a class of supermassive black hole systems known for their intense multi-wavelength emissions and violent variability. Determining the redshifts of AGNs is essential for understanding their distances, which, in turn, sheds light on our current understanding of the structure of the nearby universe. However, the task involves a number of challenges, such as the need for meticulous follow-up observations across multiple wavelengths and astronomical facilities. In this study, we employ a simple yet effective deep learning model with a single hidden layer having 64 neurons and a dropout of 0.25 in the hidden layer on a sample of AGNs with known redshifts from the latest AGN catalogue, 4LAC-DR3, obtained from Fermi-LAT. We utilized their spectral, spatial, and temporal properties to robustly predict the redshifts of AGNs as well quantify their associated uncertainties by modifying the model using two different variational inference methods. We achieve a correlation coefficient of 0.784 on the test set from the frequentist model and 0.777 and 0.778 from both the variants of variational inference, and, when used to make predictions on the samples with unknown redshifts, we achieve mean predictions of 0.421, 0.415, and 0.393, with standard deviations of 0.258, 0.246, and 0.207 from the models, respectively. [ABSTRACT FROM AUTHOR]

In this study, we carry out a comprehensive variability analysis of the BL Lac object 4FGL J2202.7+4216 detected by the Fermi- LAT, over a period of more than 3 yr, from 2019 April 27 to 2022 August 09. We detect the presence of quasi-periodic fluctuations with a period of ∼100 d with a confidence level exceeding 4σ. We also tentatively detect two other quasi-periodic fluctuations with a period of ∼75 and ∼50 d, which persist over the entire duration of observation. This is the first time such a variability feature pertaining to this source is being reported. We propose that the observed quasi-periodic oscillations may be related to the precession of the blazar jet with a high Lorentz factor or to the motion of a plasma blob through the helical structure of the jet. The harmonicity among the detected periodicities suggests the global p-mode oscillations of the thick disc to be a plausible mechanism as well. For a decisive conclusion on the physical origin of such fluctuation, further multiwavelength complementary observations, especially very long baseline interferometric observations, would be required. [ABSTRACT FROM AUTHOR]

Here we present the first optical photometric monitoring results of a sample of 12 newly discovered blazars from the ICRF – Gaia CRF astrometric link. The observations were performed from April 2013 to August 2019 using eight telescopes located in Europe. For a robust test for the brightness and colour variability, we use Abbé criterion and F-test. Moreover, linear fittings are performed to investigate the relation in the colour-magnitude variations of the blazars. Variability was confirmed in the case of 10 sources; two sources, 1429+249 and 1556+335 seem to be possibly variable. Three sources (1034+574, 1722+119, and 1741+597) have displayed large amplitude brightness change of more than one magnitude. We found that the seven sources displayed bluer-when-brighter variations, and one source showed redder-when-brighter variations. We briefly explain the various AGN emission models which can explain our results. [ABSTRACT FROM AUTHOR]

Flaring episodes in blazars represent one of the most violent processes observed in extra-galactic objects. Studies of such events shed light on the energetics of the physical processes occurring in the innermost regions of blazars, which cannot otherwise be resolved by any current instruments. In this work, we present some of the largest and most rapid flares captured in the optical band in the blazars 3C 279, OJ 49, S4 0954+658, TXS 1156+295, and PG 1553+113. The source flux was observed to increase by nearly ten times within a time-scale of a few weeks. We applied several methods of time series analysis and symmetry analysis. Moreover, we also performed searches for periodicity in the light curves of 3C 279, OJ 49 and PG 1553+113 using the Lomb–Scargle method and found plausible indications of quasi-periodic oscillations (QPOs). In particular, the 33- and 22-day periods found in 3C 279, i.e. a 3:2 ratio, are intriguing. These violent events might originate from magnetohydrodynamical instabilities near the base of the jets, triggered by processes modulated by the magnetic field of the accretion disc. We present a qualitative treatment as the possible explanation for the observed large amplitude flux changes in both the source-intrinsic and source-extrinsic scenarios. [ABSTRACT FROM AUTHOR]

We present a first systematic time series study of a sample of blazars observed by the Transiting Exoplanet Survey Satellite (TESS). By cross matching the positions of the sources in the TESS observations with those from Roma-BZCAT, 29 blazars including both BL Lacerate objects and flat-spectrum radio quasars were identified. The observation lengths of the 79 light curves of the sources, across all sectors on which the targets of interest have been observed by TESS , range between 21.25 and 28.2 d. The light curves were analysed using various methods of time series analysis. The results show that the sources exhibit significant variability with fractional variability spanning between 1.41 per cent and 53.84 per cent. The blazar flux distributions were studied by applying normal and log-normal probability density function models. The results indicate that optical flux histogram of the sources are consistent with normal probability density function with most of them following bimodal distribution as opposed to unimodal distribution. This suggests that the days-time-scale optical variability is contributed either by two different emission zones or two distinct states of short-term activity in blazars. Power spectral density analysis was performed by using the power spectral response method and the true power spectra of unevenly sampled light curves were estimated. The power spectral slopes of the light curves ranged from 1.7 to 3.2. [ABSTRACT FROM AUTHOR]

In this paper, I present a qualitative discussion on the prospect of production of ultra-high photons in blazars. The sources are a subclass of active galactic nuclei which host supermassive black holes and fire relativistic jets into the intergalactic medium. The kpc-scale jets are believed to be dominated by Poynting flux and constitute one of the most efficient cosmic particle accelerators, that potentially are capable of accelerating the particles up to EeV energies. Recent IceCube detection of astrophysical neutrino emissions, in coincidence with the enhanced gamma-ray from Tev blazar TXS 0506 + 056, further supports hadronic models of blazar emissions in which particle acceleration processes, such as relativistic shocks, magnetic re-connection, and relativistic turbulence, could energize hadrons, e.g., protons, up to energies equivalent to billions of Lorentz factors. The ensuing photo-pionic processes may then result in gamma-rays accompanied by neutrino flux. Furthermore, the fact that blazars are the dominant source of observed TeV emission encourages search for signatures of acceleration scenarios that would lead to the creation of ultra-high-energy photons. [ABSTRACT FROM AUTHOR]

The study of short-term variability properties in AGN jets has the potential to shed light on their particle acceleration and emission mechanisms. We report results from a 4-d coordinated multiwavelength campaign on the highly peaked blazar (HBL) Mkn 421 in 2019 January. We obtained X-ray data from AstroSAT, BVRI photometry with the Whole Earth Blazar Telescope (WEBT), and TeV data from First G-APD Cherenkov Telescope to explore short-term multiwavelength variability in this HBL. The X-ray continuum is rapidly variable on time-scales of tens of ks. Fractional variability amplitude increases with energy across the synchrotron hump, consistent with previous studies; we interpret this observation in the context of a model with multiple cells whose emission spectra contain cutoffs that follow a power-law distribution. We also performed time-averaged and time-resolved (time-scales of 6 ks) spectral fits; a broken power-law model fits all spectra well; time-resolved spectral fitting reveals the usual hardening when brightening behaviour. Intra-X-ray cross-correlations yield evidence for the 0.6–0.8 keV band to likely lead the other bands by an average of 4.6 ± 2.6 ks, but only during the first half of the observation. The source displayed minimal night-to-night variability at all wavebands thus precluding significant interband correlations during our campaign. The broad-band SED is modelled well with a standard one-zone leptonic model, yielding jet parameters consistent with those obtained from previous SEDs of this source. [ABSTRACT FROM AUTHOR]

The X-ray emission from blazars has been widely investigated using several space telescopes. In this work, we explored statistical properties of the X-ray variability in the blazars S5 0716+714, OJ 287, Mkn 501, and RBS 2070 using the archival observations from the XMM-Newton telescope between the period 2002–2020. Several methods of timing and spectral analyses, including fractional variability, minimum variability time-scale, power spectral density analyses, and countrate distribution, were performed. In addition, we fitted various spectral models to the observations, as well as estimated hardness ratio. The results show that the sources are moderately variable within the intraday time-scale. Three of the four sources exhibited a clear bi-modal pattern in their countrate distribution, revealing possible indication of two distinct countrate states, that is, hard and soft countrate states. The slope indices of the power spectral density were found to be centred around 0.5. Furthermore, the spectra of the sources were fitted with single power law, broken power law, log-parabolic, and blackbody + log-parabolic models (the latter only for OJ 287). We conclude that for most of the observations log-parabolic model was the best fit. The power-spectral-density analysis revealed the variable nature of PSD slopes in the source light curves. The results of this analysis could indicate the non-stationary nature of the blazar processes on intraday time-scales. The observed features can be explained within the context of current blazar models, in which the non-thermal emission mostly arises from kilo-pc scale relativistic jets. [ABSTRACT FROM AUTHOR]

The Cosmic Ray Extremely Distributed Observatory (CREDO) pursues a global research strategy dedicated to the search for correlated cosmic rays, so-called Cosmic Ray Ensembles (CRE). Its general approach to CRE detection does not involve any a priori considerations, and its search strategy encompasses both spatial and temporal correlations, on different scales. Here we search for time clustering of the cosmic ray events collected with a small sea-level extensive air shower array at the University of Adelaide. The array consists of seven one-square-metre scintillators enclosing an area of 10 m × 19 m. It has a threshold energy ~0.1 PeV, and records cosmic ray showers at a rate of ~6 mHz. We have examined event arrival times over a period of over 2.5 years in two equipment configurations (without and with GPS timing), recording ~300 k events and ~100 k events. We determined the event time spacing distributions between individual events and the distributions of time periods which contained specific numbers of multiple events. We find that the overall time distributions are as expected for random events. The distribution which was chosen a priori for particular study was for time periods covering five events (four spacings). Overall, these distributions fit closely with expectation, but there are two outliers of short burst periods in data for each configuration. One of these outliers contains eight events within 48 s. The physical characteristics of the array will be discussed together with the analysis procedure, including a comparison between the observed time distributions and expectation based on randomly arriving events. [ABSTRACT FROM AUTHOR]

Optical observations of a sample of 12 Îł -ray-bright blazars from four optical data archivesâ€"American Association of Variable Star Observers, Small and Moderate Aperture Research Telescope System, Catalina, and Steward Observatoryâ€"are compiled to create densely sampled light curves spanning more than a decade. As a part of the blazar multiwavelength studies, several methods of analysis, e.g., flux distribution and rmsâ€"flux relation, are performed on the observations with the aim to compare the results with the similar ones in the Îł -ray band presented in Bhatta & Dhital. It is found that, similar to the Îł -ray band, blazars display significant variability in the optical band that can be characterized with lognormal flux distribution and a power-law dependence of rms on flux. It could be an indication of a possible inherent linear rmsâ€"flux relation, yet the scatter in the data does not allow to rule out other possibilities. When comparing variability properties in the two bands, the blazars in the Îł -rays are found to exhibit stronger variability with a steeper possible linear rmsâ€"flux relation and a flux distribution that is more skewed toward higher fluxes. The cross-correlation study shows that except for source 3C 273, the overall optical and the Îł -ray emission in the sources are highly correlated, suggesting a cospatial existence of the particles responsible for both the optical and Îł -ray emission. Moreover, sources S5 0716+714, Mrk 421, Mrk 501, PKS 1424-418, and PKS 2155-304 revealed possible evidence of quasiperiodic oscillations in the optical emission with the characteristic timescales, which are comparable to those in the Îł -ray band detected in our previous work. [ABSTRACT FROM AUTHOR]

Linear time series analysis, mainly the Fourier transform-based methods, has been quite successful in extracting information contained in the ever-modulating light curves of active galactic nuclei, and thereby contribute in characterizing the general features of supermassive black hole systems. In particular, the statistical properties of γ-ray variability of blazars are found to be fairly represented by flicker noise in the temporal frequency domain. However, these conventional methods have not been able to fully encapsulate the richness and the complexity displayed in the light curves of the sources. In this work, to complement our previous study on a similar topic, we perform nonlinear time series analysis of the decade-long Fermi/LAT observations of 20 γ-ray bright blazars. The study is motivated to address one of the most relevant queries: whether the dominant dynamical processes leading to the observed γ-ray variability are of deterministic or stochastic nature. For the purpose, we perform recurrence quantification analysis of the blazars and directly measure the quantities, which suggest that the dynamical processes in blazars could be a combination of deterministic and stochastic processes, while some of the source light curves revealed significant deterministic content. The result, with possible implication of strong disk-jet connection in blazars, could prove to be significantly useful in constructing models that can explain the rich and complex multiwavelength observational features in active galactic nuclei. In addition, we estimate the dynamical timescales, so-called trapping timescales, in the order of a few weeks. [ABSTRACT FROM AUTHOR]

Smallholder farmers in Nepal are vulnerable to climate change-related extreme weather events. Adaptation in the agriculture sector is needed to mitigate social, economic, and ecological impacts from increasing levels of hazard activity. To examine this issue, a household survey of 350 farmers in the Terai region of Nepal was carried out to assess farmers' risk perceptions towards three common extreme weather events (floods, cold spells, and heat waves) and to explore their intended responses to cope with future impacts. The intended common adaptation strategies include changes in farm management, seeking off-farm employment, emergency management planning, purchasing crop insurance, and the raising of awareness. Threat appraisal is the strongest predictor of the number of intended adaptation strategies adopted in response to slow-onset hazards (heat waves and cold spells), while coping appraisal is the major predictor of the number of intended adaptation strategies adopted to mitigate flood risk, a rapid onset hazard. Crop insurance and off-farm employment are farmers' most preferred flood adaptation strategies, while crop insurance is the most preferred adaptation strategy for heat waves and cold spells. Other variables such as the number of past implemented strategies, experience with extreme events, community organisation membership, and access to credit and extension services were also significantly associated with farmers' choices for adaptation strategies in response to the three extreme events. This information can be used to tailor community-centred communication about potential threats from different extreme weather events and government technical and financial support, which will be crucial for farmers to adapt effectively to climate change-related weather extremes. [ABSTRACT FROM AUTHOR]

Quasi-periodic oscillations (QPO) originating from innermost regions of blazars can provide unique perspective of some of the burning issues in blazar studies including disk–jet connection, launch of relativistic jets from the central engine, and other extreme conditions near the fast rotating supermassive black holes. However, a number of hurdles associated with searching QPOs in blazars e.g. red-noise dominance, modest significance of the detection, and periodic modulation lasting for only a couple of cycles, make it difficult to estimate the true significance of the detection. In this work, we report a ∼ 330-d QPO in the Fermi/LAT observations of the blazar Mrk 501 spanning nearly a decade. To establish consistency of the result, we adopted multiple approaches to the time-series analysis and employed four widely known methods. Among these, the Lomb–Scargle periodogram and weighted wavelet z -transform represent frequency-domain-based methods whereas epoch folding and z-transformed discrete auto-correlation function are time-domain-based analyses. The power spectrum response method was followed to properly account for the red-noise, largely inherent in blazar light curves. Both local and global significance of the signal were found to be above 99 per cent over possible spurious detection. In the context where not many γ-ray QPOs have been reported to last more than 5 cycles, this might be one of the few instances where we witness a sub-year time-scale γ-ray QPO persisting nearly 7 cycles. A number of possible scenarios linked with binary supermassive black hole, relativistic jets, and accretion discs can be invoked to explain the transient QPO. [ABSTRACT FROM AUTHOR]

In this work, we present the results of our multi-band microvariability study of the famous blazar BL Lac. We performed microvariablity observations of the source in the optical VRI bands for four nights in 2016. We studied the intranight flux and spectral variability of the source in detail with an objective to characterize microvariability in the blazars, a frequently observed phenomenon in blazars. The results show that the source often displays a fast flux variability with an amplitude as large as ~0.2 magnitude within a few hours, and that the color variability in the similar time scales can be characterized as "bluer-when-brighter" trend. We also observed markedly curved optical spectrum during one of the nights. Furthermore, the correlation between multi-band emission shows that in general the emission in all the bands are highly correlated; and in one of the nights V band emission was found to lead the I band emission by ~13 min. The search for characteristic timescale using z-transformed auto-correlation function and the structure function analyses reveals characteristic timescale of ~50 min in one of the R band observations. We try to explain the observed results in the context of the passage of shock waves through the relativistic outflows in blazars. [ABSTRACT FROM AUTHOR]

While impacts of climate change on agricultural systems have been widely researched, there is still limited understanding of what agricultural innovations have evolved over time in response to both climatic and non-climatic drivers. Although there has been some progress in formulating national adaptation policies and strategic planning in different countries of South Asia, research to identify local-level adaptive strategies and practices is still limited. Through eight case studies and a survey of 300 households in 15 locations in India, Nepal and Bangladesh, this paper generates empirical evidence on emerging agricultural innovations in contrasting socio-economic, geographical and agro-ecological contexts. The study demonstrates that several farm practices (innovations) have emerged in response to multiple drivers over time, with various forms of institutional and policy support, including incentives to reduce risks in the adoption of innovative practice. It further shows that there is still limited attempt to systematically mainstream adaptation innovations into local, regional and national government structures, policies and planning processes. The paper shows that the process of farm-level adaptation through innovation adoption forms an important avenue for agricultural adaptation in South Asia. A key implication of this finding is that there is a need for stronger collaborations between research institutions, extension systems, civil society and the private sector actors to enhance emerging adaptive innovations at the farm level. [ABSTRACT FROM AUTHOR]

Farmers in the Indo-Gangetic Plains are constantly seeking ways to adapt to changing circumstances and opportunities that include new technologies, institutions, policies, socio-economic and cultural shifts, as well as a changing climate. The relationship between rainfall and local livelihoods is important to devise policies to improve adaptive capacity of farmers to different drivers of changes. The present study investigates whether the spatial variations in rainfall have prompted the location-specific livelihood diversification by using data from 2660 farm families in the climatic risk areas in India, Nepal and Bangladesh. The results show a higher on-farm livelihood diversification in the areas with high rainfall (1500-2100 mm) compared to medium (900-1500 mm) and very high rainfall regimes (>2100 mm). Based on this study, the optimal range of rainfall for better agricultural livelihood in the context of changing environmental circumstances is from 1500 to 2100 mm. In terms of farm practices changed (proxy of adaptability), farmers responded more frequently to the market-related drivers than climatic stressors. Farmers in climate vulnerable areas (Bihar and coastal Bangladesh for instance) responded more to climatic stressors than those living in relatively less vulnerable areas (Terai for instance). The results imply that livelihood strategies should be tailor-made along the climatic resources such as rainfall, considering other biophysical and socio-economic variations at the spatial scale. Identifying household and farm-level coping strategies along the rainfall gradient can also be useful in targeting interventions to build resilience to shocks. [ABSTRACT FROM AUTHOR]

Concerns over climate change and climatic variability are growing in South Asia because of the potential detrimental impacts of these phenomena on livelihoods. Such growing concerns demonstrate a need to assess how farmers simultaneously cope with extreme events and adapt to climatic variability. Based on household surveys of 2660 farm families conducted in Nepal's Terai, coastal Bangladesh, and the Indian state of Bihar, this paper seeks to (1) explore farmers’ coping strategies under adverse weather events; (2) identify key adaptation measures used by farmers; and (3) explore the policy interventions required to adjust agriculture to climatic variability. The study reveals that migration is the most important coping strategy of the households in Bihar and coastal Bangladesh, while reliance on credit markets is the most important in Terai. Farmers in the areas with higher rainfall variability pursue a higher number of coping strategies compared to farmers in areas with lower rainfall variability. Food available months are also higher in areas with higher rainfall variability. Across all sites, the most frequently mentioned adaptive practices are changing cropping patterns and adoption of resilient crop varieties. A large number of farmers place emphasis on breeding crop varieties that tolerate adverse weather. Governments should implement a number of planned activities to cope with adverse events, with the aim that these activities would be synergistic with adaptation to climate change. [ABSTRACT FROM PUBLISHER]

In Uganda, Ghana and Bangladesh, participatory tools were used for a socio-economic and gender analysis of three topics: climate-smart agriculture (CSA), climate analogue approaches, and climate and weather forecasting. Policy and programme-relevant results were obtained. Smallholders are changing agricultural practices due to observations of climatic and environmental change. Women appear to be less adaptive because of financial or resource constraints, because of male domination in receiving information and extension services and because available adaptation strategies tend to create higher labour loads for women. The climate analogue approach (identifying places resembling your future climate so as to identify potential adaptations) is a promising tool for increasing farmer-to-farmer learning, where a high degree of climatic variability means that analogue villages that have successfully adopted new CSA practices exist nearby. Institutional issues related to forecast production limit their credibility and salience, particularly in terms of women's ability to access and understand them. The participatory tools used in this study provided some insights into women's adaptive capacity in the villages studied, but not to the depth necessary to address women's specific vulnerabilities in CSA programmes. Further research is necessary to move the discourse related to gender and climate change beyond the conceptualization of women as a homogenously vulnerable group in CSA programmes. [ABSTRACT FROM PUBLISHER]

There is significant interest in determining the role of climate-induced shocks as a prominent driver on migration decisions of different groups of farmers in South Asia. Using data from a survey of 2,660 farm-families and focused group discussions in Bihar (India), Terai (plains) (Nepal) and coastal Bangladesh, we employed logistic regression to investigate household response towards migration and gender dimensions of adverse climatic events. The results suggest that migration decisions depend on farmers' unique resource profiles: (a) households that use migration to improve their resilience, mostly resource rich households; (b) households that have no alternative but to migrate, mostly poor farmers; and (c) households who cannot migrate due to different socio-economic obligations, mostly farmers with intermediate level of income that also includes women, children and elderly of different income profiles. These profiles represent a spectrum with households within a profile being closer to one or the other of the profiles on either side. They are not mutually exclusive and serve as a point of departure for further research to refine key explanatory variables. Given that some members of the household pursue migration as a result of adverse climatic events, government strategies are required to mitigate risks at destinations and create opportunities for the trapped populations. [ABSTRACT FROM AUTHOR]

Despite growing scientific consensus that agriculture is affected by climate change and variability, there is still limited knowledge on how agricultural systems respond to climate risks under different circumstances. Drawing on three case studies conducted in the Indo-Gangetic Plains, covering Nepal, Bangladesh, and the Indian state of Punjab, this article analyzes agricultural adaptation practices to climate change. In particular, we examine how farmers and other agricultural actors understand and respond to climate change. We identify a variety of adaptation practices related to changes in cropping system, technological innovations, and institutional changes. We also explore key challenges related to such emerging adaptive innovation processes in the region. [ABSTRACT FROM AUTHOR]

We present the results of a long-term study designed to investigate the nature of micro-variability in blazars carried out primarily at the Southeastern Association for Research in Astronomy (SARA) observatories. We analyzed micro-variability data of fifteen OVV quasars and BL Lac sources collected from 1995 to 2021. The data set consists of single-band light curves interspersed with multi-color and micro-variability observations. This paper reports over 900 nights of CCD observations. We also incorporated observations from other observers as well as observations gleaned from the literature into our analysis. We employed differential photometry to measure magnitudes and then construct the long-term and micro-variability light curves. Our results indicate that there is no correlation between the presence of micro-variations and the brightness of the source. We present a viable theory to explain the intermittent micro-variability as pulses of radiation emitted by individual turbulent cells in the relativistic jet, which are stimulated by a passing shock wave. We present model fits and test results for various data sets, including WEBT light curves, Kepler light curves and a TESS light curve. Although the consensus in the community is that blazar jets must be turbulent, the identification of micro-variations as manifestations of actual turbulent cells is important for modeling these turbulent jets. We can obtain estimates of cell sizes (assuming a shock speed), and the distribution of cell sizes derived from observations is consistent with numerical simulation predictions. [ABSTRACT FROM AUTHOR]

The Cosmic-Ray Extremely Distributed Observatory (CREDO) is a newly formed, global collaboration dedicated to observing and studying cosmic rays (CR) and cosmic-ray ensembles (CRE): groups of at least two CR with a common primary interaction vertex or the same parent particle. The CREDO program embraces testing known CR and CRE scenarios, and preparing to observe unexpected physics, it is also suitable for multi-messenger and multi-mission applications. Perfectly matched to CREDO capabilities, CRE could be formed both within classical models (e.g., as products of photon–photon interactions), and exotic scenarios (e.g., as results of decay of Super-Heavy Dark Matter particles). Their fronts might be significantly extended in space and time, and they might include cosmic rays of energies spanning the whole cosmic-ray energy spectrum, with a footprint composed of at least two extensive air showers with correlated arrival directions and arrival times. As the CRE are predominantly expected to be spread over large areas and, due to the expected wide energy range of the contributing particles, such a CRE detection might only be feasible when using all available cosmic-ray infrastructure collectively, i.e., as a globally extended network of detectors. Thus, with this review article, the CREDO Collaboration invites the astroparticle physics community to actively join or to contribute to the research dedicated to CRE and, in particular, to pool together cosmic-ray data to support specific CRE detection strategies. [ABSTRACT FROM AUTHOR]

The search for periodic signals from blazars has become a widely discussed topic in recent years. In the scenario that such periodic changes originate from the innermost regions of blazars, the signals bear imprints of the processes occurring near the central engine, which are mostly inaccessible to our direct view. Such signals provide insights into various aspect of blazar studies, including disk-jet connection, magnetic-field configuration and, more importantly, strong gravity near the supermassive black holes and release of gravitational waves from binary supermassive-black-hole systems. In this work, we report the detection of a periodic signal in the radio light curve of blazar J1043+2408 spanning ∼10.5 years. We performed multiple methods of time-series analysis, namely, epoch folding, Lomb–Scargle periodogram, and discrete autocorrelation function. All three methods consistently revealed a repeating signal with a periodicity of ∼560 days. To robustly account for the red-noise processes usually dominant in the blazar variability and other possible artefacts, a large number of Monte Carlo simulations were performed. This allowed us to estimate high significance (99.9% local and 99.4% global) against possible spurious detection. As possible explanations, we discuss a number of scenarios, including binary supermassive-black-hole systems, Lense–Thirring precession, and jet precession. [ABSTRACT FROM AUTHOR]