Modelling variability of solar activity cycles

Context. Solar activity cycles vary in amplitude and duration. The variations can be at least partly explained by fluctuations in dynamo parameters. Aims. We want to restrict uncertainty in fluctuating dynamo parameters and find out which properties of the fluctuations control the amplitudes of the magnetic field and energy in variable dynamo cycles. Methods. A flux-transport model for the solar dynamo with fluctuations of the Babcock-Leighton type $\alpha$-effect was applied to generate statistics of magnetic cycles for our purposes. The statistics were compared with data on solar cycle periods to restrict the correlation time of dynamo fluctuations. Results. A characteristic time of fluctuations in the $\alpha$-effect is estimated to be close to the solar rotation period. The fluctuations produce asymmetry between the times of rise and descent of dynamo cycles, the rise time being on average shorter. The affect of the fluctuations on cycle amplitudes depends on the phase of the cycle in which the fluctuations occur. Negative fluctuations (decrease in $\alpha$) in the rise phase delay decay of poloidal field and increase the cycle amplitude in toroidal field and magnetic energy. Negative fluctuation in the decline phase reduces the polar field at the end of a cycle and the amplitude of the next cycle. The low amplitude of the 24th solar cycle compared to the preceding 23rd cycle can be explained by this effect. Positive fluctuations in the descent phase enhance the magnetic energy of the next cycle by increasing the seed poloidal field for the next cycle. The statistics of the computed energies of the cycles suggest that superflares of $\ge 10^{34}$ erg are not possible on the Sun.Comment: 8 pages, 11 figures, A&A (accepted

Направляемый свойством поиск реляционных инвариантов

Property Directed Reachability (PDR) is an efficient and scalable approach to solving systems of symbolic constraints also known as Constrained Horn Clauses (CHC). In the case of non-linear CHCs, which may arise, e.g., from relational verification tasks, PDR aims to infer an inductive invariant for each uninterpreted predicate. However, in many practical cases this reasoning is not successful, as invariants should be derived for groups of predicates instead of individual predicates. The article describes a novel algorithm that identifies these groups automatically and complements the existing PDR technique. The key feature of the algorithm is that it does not require a possibly expensive synchronization transformation over the system of CHCs. We have implemented the algorithm on top of a up-to-date CHC solver Spacer. Our experimental evaluation shows that for some CHC systems, on which existing solvers diverge, our tool is able to discover relational invariants.Достижимость, направляемая свойством, (Property Directed Reachability, PDR) — эффективный и масштабируемый подход к решению систем символьных ограничений, известных как дизъюнкты Хорна с ограничениями (Constrained Horn Clauses, CHC). В случае нелинейных систем дизъюнктов, которые могут возникнуть, к примеру, из задач реляционной верификации, PDR выводит индуктивные инварианты для каждого неинтерпретированного предикатного символа. Тем не менее на практике автоматический вывод таких решений не удаётся, т.к. инварианты должны выводиться для групп предикатных символов вместо индивидуальных предикатных символов. В статье описан новый алгоритм, автоматически определяющий такие группы и обобщающий существующий подход PDR. Ключевая особенность алгоритма состоит в том, что он не требует потенциально дорогой синхронизирующей трансформации системы дизъюнктов Хорна. Алгоритм был реализован над современным решателем дизъюнктов Хорна Spacer. Эксперименты показывают, что полученная реализация успешно выводит реляционные инварианты для некоторых систем дизъюнктов, на которых существующие решатели не завершаются

CYBERCRIME IN RUSSIA: CURRENT CHALLENGES AND GOOD PRACTICES IN COMBATING CYBERCRIME

Globalization and the rapid development of computer and IT technologies have led to the emergence of a new type of offence — cybercrime. This concept has not yet been legislated, and there is a problem of classification of crimes committed in cyberspace. The authors offer an analysis of current state of cybercrime in Russia for the last 10 years. An overview of modern countermeasures of cybercrime in Russia and abroad is presented. Some recommendations for ensuring corporate cyber security and promising areas of research are outlined

Transport coefficients of He+ ions in helium

Recent theoretical advances have made it possible to calculate ab initio interaction potentials for atomic ionatom collisions that are highly accurate, and to use the potentials to calculate gaseous ion transport coefficients that meet or exceed the accuracy with which they can be measured1-4. Hence gaseous ion transport data serve as stringent tests of the interaction potentials. Advances in the calculation of transport properties, unfortunately, have not included the situation where atomic ions move through their parent gases, where resonant charge transfer (RCT) can occur. The purpose of this paper is to fill this void

Influence of El Niño on parameters of the middle and upper atmosphere over Eastern Siberia according to reanalysis and model data in winter

One of the most important climate-forming phenomena in the ocean—atmosphere system is the El Niño Southern Oscillation (ENSO) events, which manifest themselves with varying intensity in almost all regions of the globe. The central regions of Eurasia are farthest from the tropics of the Pacific Ocean, the regions where ENSO originates. There are different points of view regarding the nature of the ENSO effect on these regions. In the presented work, the influence of ENSO on the upper atmosphere of the Northern Hemisphere and, in particular, on the upper atmosphere of Eastern Siberia is estimated using model calculations and reanalysis data. The results of the analysis show that the large-scale structures of the atmospheric response to the ENSO events in the Northern Hemisphere are similar according to modeling and reanalysis, yet the regions of Eastern Siberia are on the periphery of the main signal and there are significant differences in estimated effects from one case of El Niño and La Niña to another. In January, ENSO has the greatest impact on the middle atmosphere of the polar regions of the Northern Hemisphere. Over Eurasia and Eastern Siberia, the atmospheric response to the ENSO events turned out to be weak or absent