Browsing by Author "Pawan Kumar"

Now showing 1 - 20 of 24

A new asymmetric loss function for estimation of any parameter
(DAV College, 2020) Dinesh Kumar; Pawan Kumar; Pradip Kumar; Umesh Singh; Prashant Kumar Chaurasia
A new asymmetric loss function which is suitable for estimation of location as well as scale and other parameters has been introduced. To check the superiority of the proposed loss function over some existing and exploited loss functions such as squared error loss function (SELF), general entropy loss function (GELF), LINEX loss function and Logarithmic-SELF (LSELF), we have calculated the Bayes estimators of the parameterθ of exponential distribution under SELF, GELF, LINEX loss function, Logarithmic- SELF (LSELF) and the proposed exponential squared error loss function (ESELF) for complete sample from the exponential distribution. A data set has been considered to show its application to the real problems. The simulation study is carried out to compare the performance of Bayes estimators in terms of their posterior risks. © 2020 DAV College. All rights reserved.
Beneficial elements: New Players in improving nutrient use efficiency and abiotic stress tolerance
(Springer Science and Business Media B.V., 2023) Rajesh Kumar Singhal; Shah Fahad; Pawan Kumar; Prince Choyal; Talha Javed; Dinesh Jinger; Prabha Singh; Debanjana Saha; Prathibha Md; Bandana Bose; H. Akash; N.K. Gupta; Rekha Sodani; Devanshu Dev; Dalpat Lal Suthar; Ke Liu; Matthew Tom Harrison; Shah Saud; Adnan Noor Shah; Taufiq Nawaz
Plant requires seventeen essential mineral elements for proper growth and functioning classified as macro and micro-nutrients. Apart from these, cerium (Ce), cobalt (Co), iodine (I), aluminum (Al), selenium (Se), sodium (Na), lanthanum (La), silicon (Si), titanium (Ti), and vanadium (V) are evolving as pivotal bio-stimulants in plant growth and providing stress tolerance. Although, they are not mandatory for all plants directly but when they are supplemented, promote the plant growth positively and simulate multiple abiotic and biotic stresses tolerance. Though, these elements have crucial role in plant growth, still obscurethe uptake, transport and molecular understanding as much of macro and micronutrients. However, in recent years scientists are giving more emphasis to explore their mechanisms associated with enhancing antioxidant defense, stress responsive proteins accumulation, and transcription factors under variety of stresses. Likely, they are also crosstalk with other essential elements and plant growth regulators (PGRs) (salicylic acid, SA; jasmonic acid, JA), which is crucial for signaling network perception and regulate plant growth. Recent technologies developed in the field of nanotechnology assist in the further understanding of their uptake, transport and functions at cellular level andoptimizing their concentrations for better plant growth. Bio-fortification of crops with beneficial elements provides some cues regarding their importance in plant growth and also in human balance nutrition. To considering the importance of these compound, this review aimed to explore the uptake and transport mechanisms of beneficial elements and their function in plant development. Consequently, we pinpoint the crosstalk’s between PGRs and other mineral elements, which advance their crucial role during plant mineral nutrition and growth signaling. At the end, this review focused on the crucial role and mechanisms associated with these elements under multiple abiotic stresses that open exciting avanues in several directions related to crop stress breeding program. © 2022, The Author(s), under exclusive licence to Springer Nature B.V.
Bioaccumulation of fluoride in plants and its microbially assisted remediation: A review of biological processes and technological performance
(MDPI, 2021) Rakesh Kumar; Rama Sinha; Pushpa Kumari Sharma; Nishita Ivy; Pawan Kumar; Nishi Kant; Aprajita Jha; Prakash Kumar Jha; Pankaj Kumar Gupta; Prabhakar Sharma; Rakesh Kumar Singh; Rajeev Pratap Singh; Ashok Ghosh; P.V. Vara Prasad
Fluoride is widely found in soil–water systems due to anthropogenic and geogenic activities that affect millions worldwide. Fluoride ingestion results in chronic and acute toxicity, including skeletal and dental fluorosis, neurological damage, and bone softening in humans. Therefore, this review paper summarizes biological processes for fluoride remediation, i.e., bioaccumulation in plants and microbially assisted systems. Bioremediation approaches for fluoride removal have recently gained prominence in removing fluoride ions. Plants are vulnerable to fluoride accumulation in soil, and their growth and development can be negatively affected, even with low fluoride content in the soil. The microbial bioremediation processes involve bioaccumulation, biotransformation, and biosorption. Bacterial, fungal, and algal biomass are ecologically efficient bioremediators. Most bioremediation techniques are laboratory-scale based on contaminated solutions; however, treatment of fluoride-contaminated wastewater at an industrial scale is yet to be investigated. Therefore, this review recommends the practical applicability and sustainability of microbial bioremediation of fluoride in different environments. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
Dependency modeling of a SOA based system through colored Petri Nets
(University of Zagreb, 2016) Pawan Kumar; Ratneshwer Gupta
Dependency relationships play an important role in testing, maintenance and configuration management of software systems. The informal dependency representations fail to observe behavioral connections among subsystems and cause ambiguity in representing different types of dependency relationships. Therefore, dependency in a software system requires a formal and unambiguous representation so that its correct effects can be visualized. In this paper, we present a Colored Petri Net based dependency analysis of a Service Oriented Architecture (SOA) based system that represents specification of dependency relationships and models the dependencies in a SOA based system at conceptual level. Different types of dependency relations are represented in a formal manner by using Service Algebra. A module SOA based system 'Online Bookshop' has been developed and used for the purpose of modeling and example demonstration. Such modeling can help in identification of inconsistency among services, and web services can be verified for safety and reliability.
Does unintended birth lead to zero dose of DPT vaccine among children aged 12–23 months in India?
(Taylor and Francis Ltd., 2024) Pritu Dhalaria; Pawan Kumar; Ajay Verma; Pretty Priyadarshini; Ajeet Kumar Singh; Bhupendra Tripathi; Arindam Ray
Zero-dose children pose a key challenge in immunization programs due to their association with access to the health system and primary healthcare services. Examining zero-dose aids an in-depth understanding of healthcare disparities among children and caregivers. The disparity in utilization of maternal and child health services raises concerns about the potential consequences of unintended pregnancies on vaccine uptake. The National Family Health Survey 2019–21 (NFHS-5) served as the data source, and the study analyzed information from 43,247 children aged 12–23 months. Sociodemographic variables such as birth order, wealth quintile, gender, social group, religion, residence, mother education, and delivery-related factors were considered. Statistical analysis involved weighted estimates, chi-square tests, and multivariate multinomial logistic regression. The results show that 9.14% of children from unintended pregnancies were zero-dose for the DPT vaccine, compared to only 6.69% of children from intended pregnancies in India, indicating a higher prevalence of zero-dose associated with unintended pregnancies. The regression analysis shows the adjusted odds among children from an unintended birth − 1.21 times higher for the zero-dose DPT vaccine as compared to the intended birth (AOR: 1.21, 95% CI: 1.06,1.38). Zero-dose immunization has become a crucial metric of childhood immunization performance, gaining prominence in national agendas, the IA 2030 framework, and Gavi’s 2021–25 strategy. The study findings highlight a significant association between unintended pregnancy and zero-dose DPT vaccination. The results provide compelling evidence that unintended pregnancies could be a potential risk factor for zero-dose DPT vaccination in low- and middle-income countries. © 2024 The Author(s). Published with license by Taylor & Francis Group, LLC.
Drought stress responses and inducing tolerance by seed priming approach in plants
(Elsevier B.V., 2022) Debanjana Saha; Prince Choyal; Udit Nandan Mishra; Prajjal Dey; Bandana Bose; Prathibha MD; Narendra Kumar Gupta; Brijesh Kumar Mehta; Pawan Kumar; Saurabh Pandey; Jyoti Chauhan; Rajesh Kumar Singhal
Field crops are subjected to drought at different growth stages and cause for substantial yield loss in major crops, thus threaten to global food security. The crop researcher have evaluated numerous physiological, biochemical and molecular strategies to combat drought stresses but these approaches are not enough in present scenario. Therefore, it is argued that plants can be primed by assorted organic and in-organic promoters for excelling fortitude under stress conditions. Hence, seed priming with different agents is an auspicious area of research in stress biology and crop stress management, for conferring tolerance when plants are subjected to drought stress. However, the adaptation and tolerance mechanisms of drought stress are complex and quantitative in nature, which have been explored at physiological, biochemical and molecular levels thoroughly in this review. The concept of stress memory and its implication in future generation has also been discussed. Finally, in this review the challenges and opportunities of seed priming with effective application in crop stress management along with expanding the knowledge on deep understanding of drought stress tolerance to reduce the future yield gap are discussed thoroughly. © 2022
ESTIMATION AND APPLICATION OF A NEW GENERALIZATION OF EXPONENTIAL DISTRIBUTION
(Gnedenko Forum, 2025) Deepak Kumar; Prashant Kumar Chaurasia; Pawan Kumar; A. Sahoo
In statistical literature, several lifetime distributions exist for real phenomena. And one of the methods to find new lifetime distribution by existing baseline distribution such a method is known as the transformation method. In this article, we proposed a generalization of the existing transformation by introducing the additional shape parameter. Here, we considered baseline distributions as an exponential distribution. Various statistical properties of the new lifetime distribution, such as survival function, hazard rate function, cumulative hazard rate function, moments, quantile function, and order statistics, have been discussed. Demonstrate the applicability and suitability of the proposed distribution. Here, we focus only on the estimation of the parameters likes MLE, LSE and also to check long-run behaviour of the estimators. © 2025, Gnedenko Forum. All rights reserved.
Exploring landscape of measles vaccination coverage: A step towards measles elimination goal in India
(Elsevier Ltd, 2024) Pritu Dhalaria; Pawan Kumar; Ajay Verma; Pretty Priyadarshini; Ajeet Kumar Singh; Bhupendra Tripathi; Gunjan Taneja
Introduction: Measles remains a critical public health concern causing significant morbidity and mortality globally. Despite the success of measles vaccination programs, challenges persist, particularly in India. This study investigates dose-wise measles vaccination coverage and explores gaps in immunization focusing on zero-dose, one-dose, and two-dose coverage among children aged 24–35 months. Data sources and methodology: The National Family Health Survey 2019–21 (NFHS-5) served as the data source and the study analyzed information from 43,864 children aged 24–35 months. Sociodemographic variables such as birth order, wealth quintile, gender, social group, religion, residence, mother education, delivery-related factors, and media exposure were considered. Statistical analysis involved weighted estimates, chi-square tests, and multivariate multinomial logistic regression. Results: The study revealed that challenges persist in achieving optimal measles vaccination coverage. Analysis by sociodemographic factors highlighted disparities in coverage, with variations in zero dose prevalence across states and districts. The percentage of zero-dose children was significantly higher, with 11.5% of children in India remaining to receive any measles vaccination. Factors influencing vaccine coverage include birth order, age, wealth quintile, social group, religion, residence, maternal education, place of delivery, media exposure, and mode of delivery. The findings from the spatial analysis show the clustering of zero-dose children is high in the northeastern states of India. Discussion: Measles zero-dose children pose a significant obstacle to achieving elimination goals. Spatial analysis identifies clusters of unvaccinated populations guiding targeted interventions. The study aligns with global initiatives such as the Immunization Agenda 2030 emphasizing equitable vaccine access and discusses how India can tailor its strategies to achieve the goal. Lessons from polio eradication efforts inform strategies for measles elimination, stressing the importance of high-quality data and surveillance. The study underscores the urgency of addressing last-mile measles vaccination gaps in India. Spatially targeted interventions informed by sociodemographic factors can enhance immunization coverage. Achieving measles elimination requires sustained efforts and leveraging lessons from successful vaccination campaigns. The study findings have the potential to contribute to informed decision-making, supporting India's roadmap for the measles and rubella elimination goal. © 2024 The Author(s)
Exploring the reliability of polar field rise rate as a precursor for an early prediction of solar cycle
(Oxford University Press, 2023) Akash Biswas; Bidya Binay Karak; Pawan Kumar
The prediction of the strength of an upcoming solar cycle has been a long-standing challenge in the field of solar physics. The inherent stochastic nature of the underlying solar dynamo makes the strength of the solar cycle vary in a wide range. Till now, the polar precursor methods and the dynamo simulations that use the strength of the polar field at the cycle minimum to predict the strength of the following cycle have gained reasonable consensus by providing convergence in the predictions for Solar Cycles 24 and 25. Recently, it has been shown that just by using the observed correlation of the polar field rise rate with the peak of the polar field at the cycle minimum and the amplitude of the following cycle, a reliable prediction can be made much earlier than the cycle minimum. In this work, we perform surface flux transport (SFT) simulations to explore the robustness of this correlation against the stochastic fluctuations of bipolar magnetic region (BMR) tilt properties including anti-Joy and anti-Hale type anomalous BMRs, and against the variation of meridional flow speed. We find that the observed correlation is a robust feature of the solar cycles and thus it can be utilized for a reliable prediction of the solar cycle much earlier than the cycle minimum - the usual landmark of the solar cycle prediction. © 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
High yield synthesis of electrolyte heating assisted electrochemically exfoliated graphene for electromagnetic interference shielding applications
(Royal Society of Chemistry, 2015) Prashant Tripathi; Ch. Ravi Prakash Patel; Abhishek Dixit; Avanish Pratap Singh; Pawan Kumar; M.A. Shaz; Ritu Srivastava; Govind Gupta; S.K. Dhawan; Bipin Kumar Gupta; O.N. Srivastava
Herein, we demonstrate a facile one pot synthesis of graphene nanosheets by electrochemical exfoliation of graphite. In the present study, we report a significant increase in the yield of graphene by electrolyte heating assisted electrochemical exfoliation method. The obtained results of heating assisted electrochemically exfoliated graphene (utilizing H2SO4 + KOH + DW) synthesis clearly exhibit that the yield increases ∼4.5 times i.e. from ∼17% (room temperature) to ∼77% (at 80°C). A plausible mechanism for the enhanced yield based on lattice expansion and vibration of intercalated ions has been put forward and discussed in details. The quality of graphene was examined by Raman, XPS, FTIR, AFM, SEM, TEM/HRTEM and TGA techniques. The Raman as well as morphogenesis results confirm the quality of the graphene nanosheets. We have used this graphene as electromagnetic interference shielding material where a comparatively large quantity of graphene is required. This graphene exhibits enhanced shielding effectiveness (46 dB at 1 mm thickness of stacked graphene sheets in frequency region 12.4 to 18 GHz) as compared to conventional electromagnetic interference shielding materials, which is greater than the recommended limit (∼30 dB) for techno-commercial applications. Thus the present work is suggestive for future studies on enhancement of yield of high quality graphene by proposed method and the use of synthesized graphene in electromagnetic interference shielding and other possible applications. © The Royal Society of Chemistry 2015.
High-performance field emission device utilizing vertically aligned carbon nanotubes-based pillar architectures
(American Institute of Physics Inc., 2018) Bipin Kumar Gupta; Garima Kedawat; Amit Kumar Gangwar; Kanika Nagpal; Pradeep Kumar Kashyap; Shubhda Srivastava; Satbir Singh; Pawan Kumar; Sachin R. Suryawanshi; Deok Min Seo; Prashant Tripathi; Mahendra A. More; O.N. Srivastava; Myung Gwan Hahm; Dattatray J. Late
The vertical aligned carbon nanotubes (CNTs)-based pillar architectures were created on laminated silicon oxide/silicon (SiO2/Si) wafer substrate at 775 °C by using water-assisted chemical vapor deposition under low pressure process condition. The lamination was carried out by aluminum (Al, 10.0 nm thickness) as a barrier layer and iron (Fe, 1.5 nm thickness) as a catalyst precursor layer sequentially on a silicon wafer substrate. Scanning electron microscope (SEM) images show that synthesized CNTs are vertically aligned and uniformly distributed with a high density. The CNTs have approximately 2-30 walls with an inner diameter of 3-8 nm. Raman spectrum analysis shows G-band at 1580 cm-1 and D-band at 1340 cm-1. The G-band is higher than D-band, which indicates that CNTs are highly graphitized. The field emission analysis of the CNTs revealed high field emission current density (4mA/cm2 at 1.2V/μm), low turn-on field (0.6 V/μm) and field enhancement factor (6917) with better stability and longer lifetime. Emitter morphology resulting in improved promising field emission performances, which is a crucial factor for the fabrication of pillared shaped vertical aligned CNTs bundles as practical electron sources. © 2018 Author(s).
Immunomodulatory effect of dietary Spirulina platensis in type II collagen induced arthritis in rats
(2010) Narendra Kumar; Pawan Kumar; Surendra Singh
Spirulina platensis, a filamentous, multicellular microalga, is grown in certain countries as food for human and animal consumption. It is also used to derive additives in pharmaceuticals and foods. The present study was undertaken to examine the immunomodulatory effect of S. platensis in collagen induced arthritis (CIA) in rats. From the zero day of induction of arthritis, S. platensis (200 and 400 mg kg-1) was administered orally to arthritic rats up to 45 days. The arthritis score, serum pro-inflammatory cytokine, anti-collagen antibody level, delayed type hypersensitivity (DTH) response to collagen and histology of paw joints were measured as marker of inflammation in arthritis. S. platensis significantly reduced the levels of pro-inflammatory cytokine (TNF-α, IL-1β and IL-6), arthritis score and synovial cell infiltration that had been increased in arthritic rats. Conclusion: These finding indicates that S. platensis had immunomodulatory effect via modulation of multiple pathways of inflammation.
Influence of Dy3+doping concentration on crystal structure and optical absorption of SnO2nanoparticles
(Elsevier Ltd, 2021) Pawan Kumar; Monu Jakhar; Vaibhav Chauhan; Praveen C. Pandey
The present work focuses on studying the effect of Dy doping on the structural and optical properties of SnO2nanoparticles. We prepared the pure and Dy3+(1, 2, 3 and 4 at %) doped SnO2nanoparticles sample using the co-precipitation method. Three different techniques XRD, UV- Vis & FTIR spectroscopy, have been used to characterize the prepared sample. X- Ray diffraction was used to determine the crystal structure and crystallite size of the prepared sample. Structural analysis by XRD confirms the substitution of Dy3+atoms on the sites of the host matrix (SnO2). Tetragonal rutile structure is formed by pure and Dy- doped at different concentrations. UV-VIS spectroscopy was used to study the optical properties of the sample. Optical study shows that the prepared sample is highly transparent and absorption increases with Dy doping concentration due to the increase of defect state. The band gap of the sample was found to decrease with increasing Dy concentration, this is due to defect level formation below the conduction band. FTIR spectroscopy determines the molecular geometry, inter and intermolecular interaction and type of functional group present in the prepared sample. © 2021 Elsevier Ltd. All rights reserved.
Lanthanide doped dual-mode nanophosphor as a spectral converter for promising next generation solar cells
(2014) A.K. Singh; S.K. Singh; Pawan Kumar; Bipin Kumar Gupta; R. Prakash; S.B. Rai
Herein, we have successfully synthesized a lanthanide based dual-mode nanophosphor (Y0.975Yb0.020 Ho0.005VO4), capable to emit both by down-shifting and upconversion processes, via facile combustion method. The dual-mode emission in phosphor materials is still an unexplored area. The present work covers the study of structure, surface morphology, luminescent behavior and decay profile of the synthesized nanophosphor. The nanophosphor exhibits strong green emission (corresponding to 5F4, 5S2 → 5I8 transition of Ho3+ ion) on UV excitation (λex = 318 nm), via an excited state energy transfer from the charge transfer band of [VO4]3- to 5F4 state of Ho3+ ions. On the other hand, an efficient red emission of Ho3+ (5F5 → 5I8) is obtained upon infrared excitation (λex = 976 nm). We propose that the dual-mode nanophosphor could be an exceptional prospect to incorporate in next generation solar cell applications. © 2014 by American Scientific Publishers.
PCM Transformation: Properties and Their Estimation
(River Publishers, 2021) Dinesh Kumar; Pawan Kumar; Pradip Kumar; Sanjay Kumar Singh; Umesh Singh
In the present piece of work, we are going to propose a new trigonometry based transformation called PCM transformation. We have been obtained its various statistical properties such as survival function, hazard rate function, reverse-hazard rate function, moment generating function, median, stochastic ordering etc. Maximum Likelihood Estimator (MLE) method under classical approach and Bayesian approaches are tackled to obtain the estimate of unknown parameter. A real dataset has been applied to check its fitness on the basis of fitting criterions Akaike Information criterion (AIC), Bayesian Information criterion (BIC), log-likelihood (-LL) and Kolmogrov-Smirnov (KS) test statistic values in real sense. A simulation study is also being conducted to assess the estimator’s long-term attitude and compared over some chosen distributions. © 2021 River Publishers.
Preliminary investigation reveals novel pathological consequences of bluetongue virus-1 infection in the endocrine glands of pregnant Indian sheep
(Taylor and Francis Ltd., 2024) Rohit Singh; Karam Pal Singh; Rajendra Singh; Vidya Singh; Pawan Kumar; Rajat Varshney; Akanksha Yadav; Akash Mote; Mukesh Gangwar; N. Babu Prasath
Bluetongue virus (BTV), a major peril to the sheep industry, infects a wide range of the cells in the infected animals including mononuclear, dendritic and epithelial cells. However, little is known about its tropism for the secretory epithelial cells of endocrine glands and the pathogenesis it induces. The aim of the study was to assess the BTV load, antigen distribution in the tissue of the pituitary, thyroid as well as adrenal glands and associated histopathological consequences. BTV antigens were localized using immunohistochemistry in the thyroid’s epithelial cells, zona fasciculata and zona reticularis cells and the anterior pituitary epithelial cells. The real-time PCR portrayed the high viral load in adrenals at 7th days postinoculation (DPI) and in thyroid and pituitary glands at 15th DPI. Serum examination revealed variation in the T-3 and T-4 of infected animals in comparison to the control group. Caspase-3 immunolocalization revealed BTV-1 induces apoptosis in the affected cells of endocrine gland of infected animals. Further, this study signifies the tropism of BTV in the novel sites (endocrine glands) of the host that might be one of the reasons for the poor performance of infected animals. © 2023 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
Probing the variations in the timing of the Sun's polar magnetic field reversals through observations and surface flux transport simulations
(Oxford University Press, 2023) Elena M. Golubeva; Akash Biswas; Anna I. Khlystova; Pawan Kumar; Bidya Binay Karak
The polar field reversal is a crucial process in the cyclic evolution of the large-scale magnetic field of the Sun. Various important characteristics of a solar cycle, such as its duration and strength, and also the cycle predictability, are determined by the polar field reversal time. While the regular measurements of solar magnetic field have been accumulated for more than half a century, there is no consensus in the heliophysics community concerning the interpretation of the Sun's polar field measurements and especially the determination of polar field reversal time. There exists a severe problem of non-reproducibility in the reported results even from studies of the same observational data set, and this causes an obstacle to make more accurate forecasts of solar cycle. Here, we analyze the solar magnetograms from four instruments for the last four cycles, to provide a more correct interpretation of the polar field observations and to find more accurate time of the reversals. We show the absence of triple (multiple) reversals in Cycles 21-24, significant variations in the time interval between reversals in the hemispheres and in the time interval between a reversal and a cycle beginning. In order to understand the origin of the reversal time variation, we perform Surface Flux Transport (SFT) simulations and find out that the presence of the 'anomalous' bipolar magnetic regions (BMRs) in different phases of a cycle can cause cycle-to-cycle variations of the reversal time within the similar range found in observations. © The Author(s) 2023 .
Size Determination in Chemically Grown PbS Nano Particles Using Different Theoretical Approach
(John Wiley and Sons Inc, 2023) Vinay Kumar; Pranav Kumar; B. Bhattacharya; Mustafa A. Alheety; Ibrahim Zakariya'u; Pawan Kumar
Chemical bath method is adopted for growth of lead sulfide nano particles in methanolic solution of Pb(No3)2. Sulfur exchange is achieved by the controlled reaction of Na2S. The optical absorption studies have been done for obtained colloidal solution. The prepared particles are characterized by UV/Visible absorption spectra in the range 700–250 nm and the corresponding energy band gaps have been calculated assuming the effective masses of the electrons and holes in the nano particles to be same as that of bulk. The particle size has been determined by using the Wang Mahler and Brus L.E. Theoretical approaches. It is found that without using any capping agent the band gap of the compound gradually increases as the size of the particle decreases. © 2023 Wiley-VCH GmbH.
Solar cycle variability induced by stochastic fluctuations of BMR properties and at different amounts of dynamo supercriticality
(Cambridge University Press, 2023) Pawan Kumar
Understanding the irregular variation of the solar cycle is crucial due to its significant impact on global climates and the heliosphere. Since the polar magnetic field determines the amplitude of the next solar cycle, variations in the polar field can lead to fluctuations in the solar cycle. We have explored the variability of the solar cycle at different levels of dynamo supercriticality. We observe that the variability depends on the dynamo operation regime, with the near-critical regime exhibiting more variability than the supercritical regime. Furthermore, we have explored the effects of the irregular BMR properties (emergence rate, latitude, tilt, and flux) on the polar field and the solar cycle. We find that they all produce considerable variation in the solar cycle; however, the variation due to the tilt scatter is the largest. © The Author(s), 2024.
Some features of plasma bubble induced scintillations during the AICPITS campaigns of 1991
(2007) P.N. Vijayakumar; T.R. Tyagi; Lakha Singh; H. Chandra; G.D. Vyas; D.R.K. Rao; B.M. Pathan; A. Iype; B. Ramsekaran; A. Naidu; S.M. Sadique; K.N. Iyer; K.N. Pathak; A.K. Gwal; Sushil Kumar; R.P. Singh; U.P. Singh; Birbal Singh; Pawan Kumar; G.N. Navneeth; P.V.S. Koparkar; P.V.S. Ramarao; P.T. Jaychandran; P. Sriram; R. Sethuraman; A. Dasgupta; K. Basu; R.G. Rastogi
The VHF scintillations were recorded at a chain of low-latitude stations in India as part of the All India Coordinated Programme of Ionospheric and Thermospheric Studies (AICPITS), using the 244 MHz radio beacon from the geo-stationary satellite FLEETSAT which was located at 73° E longitude. Data collected during the second campaign of September-October 1991 and analyzed jointly by the participating investigators are presented. The onset times of scintillation at pairs of stations at similar latitude but different longitudes can be used to estimate the eastward drift of the scintillation patches and its E-W extent. The maximum monthly mean occurrence for September 1991 is about 35% at Trivandrum and Tiruchendur, the stations close to dip equator. Occurrence is maximum for stations Annamalainagar, Payyanur and Anantpur (50 %), located slightly north of the dip equator. It decreases further north to 30 % at Nuzvid, Bombay, 20 % near anomaly crest region, 10 % at Agra and 8 % at Delhi, which is the northern most edge of the present observations. The occurrence frequency is slightly less than that observed during the campaign of March 1991. For the sake of completeness some very interesting features and dynamical characteristics of plasma bubble induced scintillations are included here based on digital records of scintillations made at Delhi during the two equinox data campaigns in March-April 1991 and September-October 1991.