The role of nonlinear toroidal flux loss due to flux emergence in the long-term evolution of the solar cycle

A striking feature of the solar cycle is that at the beginning, sunspots appear around mid-latitudes, and over time the latitudes of emergences migrate towards the equator. The maximum level of activity varies from cycle to cycle. For strong cycles, the activity begins early and at higher latitudes with wider sunspot distributions than for weak cycles. The activity and the width of sunspot belts increase rapidly and begin to decline when the belts are still at high latitudes. However, in the late stages of the cycles, the level of activity, and properties of the butterfly wings all have the same statistical properties independent of the peak strength of the cycles. We have modelled these features using Babcock-Leighton type dynamo model and shown that the toroidal flux loss from the solar interior due to magnetic buoyancy is an essential nonlinearity that leads to all the cycles decline in the same way.Comment: IAU proceedings based on the contributed talk presented at IAU Symposium 365 in Yerevan, Armeni

Exploring the predictability of the solar cycle from the polar field rise rate: Results from observations and simulations

The inherent stochastic and nonlinear nature of the solar dynamo makes the strength of the solar cycles vary in a wide range, making it difficult to predict the strength of an upcoming solar cycle. Recently, our work has shown that by using the observed correlation of the polar field rise rate with the peak of polar field at cycle minimum and amplitude of following cycle, an early prediction can be made. In a follow-up study, we perform SFT simulations to explore the robustness of this correlation against variation of meridional flow speed, and against stochastic fluctuations of BMR tilt properties that give rise to anti-Joy and anti-Hale type anomalous BMRs. The results suggest that the observed correlation is a robust feature of the solar cycle and can be utilized for a reliable prediction of peak strength of a cycle at least 2 to 3 years earlier than the minimum.Comment: IAU proceedings based on the poster presented at IAU Symposium 365 in Yerevan, Armeni

Exploring the reliability of polar field rise rate as a precursor for an early prediction of solar cycle

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 has 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 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 solar cycle much earlier than the cycle minimum, the usual landmark of the solar cycle prediction.Comment: Under review in MNRA

Long-term modulation of solar cycles

Solar activity has a cyclic nature with the ~11-year Schwabe cycle dominating its variability on the interannual timescale. However, solar cycles are significantly modulated in length, shape and magnitude, from near-spotless grand minima to very active grand maxima. The ~400-year-long direct sunspot-number series is inhomogeneous in quality and too short to study robust parameters of long-term solar variability. The cosmogenic-isotope proxy extends the timescale to twelve millennia and provides crucial observational constraints of the long-term solar dynamo modulation. Here, we present a brief up-to-date overview of the long-term variability of solar activity at centennial--millennial timescales. The occurrence of grand minima and maxima is discussed as well as the existing quasi-periodicities such as centennial Gleissberg, 210-year Suess/de Vries and 2400-year Hallstatt cycles. It is shown that the solar cycles contain an important random component and have no clock-like phase locking implying a lack of long-term memory. A brief yet comprehensive review of the theoretical perspectives to explain the observed features in the framework of the dynamo models is presented, including the nonlinearity and stochastic fluctuations in the dynamo. We keep gaining knowledge of the processes driving solar variability with the new data acquainted and new models developed.Comment: Accepted for Space Science Revie

Superparamagnetic Nanoparticles in Exploratory Energy Research

Superparamagnetic nanoparticles are a special class of nanoparticles that exhibit hyperthermic effects when placed under an alternating magnetic field. The applications of these particles have been previously limited to biomedical fields, as an alternative to traditional cancer treatment, targeted drug delivery systems, and to enhance MRI contrast. The potential for use in energy and propulsion applications has been less explored, despite the vast promise these particles provide. The magnetic hyperthermia that results from superparamagnetism could benefit an engine’s efficiency by preheating the fuel, thus reducing the energy required to perform combustion. Two types of nanoparticles, Cu0.1Ni0.9Mn2O4 and magnetite (Fe3O4), were synthesized via the coprecipitation method and coated with oleic acid and PEG5000 to promote dispersion. These particles were then characterized using x-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). The heating properties were investigated through the use of an externally applied alternating magnetic field (AMF) and the measured corresponding temperature rise over time. This exploratory research shows great promise for the potential application of these nanoparticles as a fuel additive to enhance engine performance and suggests further research in this area should be conducted

Induced breeding, embryonic and larval development of Macrognathus pancalus (Hamilton, 1822) under captive condition

The present study was carried out to enumerate induced breeding technique and larval development of Macrognathus pancalus (Hamilton, 1822) reared under captivity. Five different doses of Ovasis hormone (T1, T2, T3, T4, and T5) with 3 replicas each were administered to the matured brooders to standardize the breeding performance of the target species. The results indicated variation in fertilization rate, latency period, egg output and hatching rate in response to different treatments. Spawning was occurred between 20-24 hrs of injection in all the experiments at 26.33±0.88°C water temperature. Among all the experimental trials, the highest fertilization rate was observed in T3 (96.15±0.60) of E2 and the highest hatching rate was observed in T3 (92.49±1.00) of E2. The present work elucidated the viability of seed production of M. pancalus reared under confined condition which will useful for aquaculture and conservation

The KiHM-9: A Novel Self-Deploying PicoSat Antenna Design for Reflectarray Antennas

Reflectarray antennas are popular on satellites for their ability to achieve similar performance to parabolic antennas in a more compact volume. This project shows how integrating novel technologies achieves the benefits of larger antennas while maintaining the advantages of small satellites. The objective of this research is to create a reflectarray antenna for a holographic metasurface that utilizes the volume surrounding a CubeSat when stowed, incorporates a novel pin-less hinge, includes a self-deploying and stabilizing joint, and is manufactured out of space-grade materials. By using hinges embedded with membranes and magnets, issues with lubrication and outgassing may be avoided, and the same motion and stability of pin-joints may be maintained with no external structure required. These technologies also result in a self-deploying and self-stabilizing design. The Radii Controlled Embedded Lamina (RadiCEL) hinge design was incorporated into the final model and allows the geometry of the hinge joint to be specifically tuned to control the stress in the hinge membrane while minimizing required hinge volume. Metal meshes were used as membrane joints, increasing the durability and robustness of the hinge. Feasibility of the RadiCEL joint is shown through fatigue testing of various materials at a range of hinge radii. The testing shows the viability of metal meshes, as well as other common membranes. Magnets were used in a MaLO configuration, which allowed for a smaller footprint in the antenna and required no external actuation or power source to deploy and stabilize the antenna. Various prototypes of the system were manufactured and are presented. Modeling and testing efforts presented create various opportunities to build on current research to improve mission capability by increasing antenna gain while eliminating peripherals required for antenna deployment

Study of self drug administration among second professional medical students

Background: Self-medication is very common in our day to day life which is an unhealthy and risky practice. Present study was done to determine the knowledge, attitude and practice among second professional medical students.Methods: A questionnaire related to self-medication with consent was prepared and distributed among the students of second professional. Data was collected and analysed the results expressed as counts and percentages.Results: Total 100 students participated in the study for taking self-medication and was no need to visit the doctor for minor illness. In maximum students, source of information of the drugs used for self-medication pharmacological based and learning process in the college. The source of drug was medical store. Most of the students took self-medication for loose motion and headache followed by cough, cold and fever. Out of total 100 students most of the students took paracetamol tablet as self-medication.Conclusions: This study showed that second professional medical students after studying pharmacological books they do not use any wrong medicine as self-medication. High level of awareness of second professional students has minimized self medication

MonkeyDB: effectively testing correctness under weak isolation levels

Modern applications, such as social networking systems and e-commerce platforms are centered around using large-scale storage systems for storing and retrieving data. In the presence of concurrent accesses, these storage systems trade off isolation for performance. The weaker the isolation level, the more behaviors a storage system is allowed to exhibit and it is up to the developer to ensure that their application can tolerate those behaviors. However, these weak behaviors only occur rarely in practice and outside the control of the application, making it difficult for developers to test the robustness of their code against weak isolation levels. This paper presents MonkeyDB, a mock storage system for testing storage-backed applications. MonkeyDB supports a key-value interface as well as SQL queries under multiple isolation levels. It uses a logical specification of the isolation level to compute, on a read operation, the set of all possible return values. MonkeyDB then returns a value randomly from this set. We show that MonkeyDB provides good coverage of weak behaviors, which is complete in the limit. We test a variety of applications for assertions that fail only under weak isolation. MonkeyDB is able to break each of those assertions in a small number of attempts. © 2021 Owner/Author