Phase dependent advection-diffusion in drift wave - zonal flow turbulence

In plasma turbulence theory, due to the complexity of the system with many non-linearly interacting waves, the dynamics of the phases is often disregarded and the so-called random-phase approximation (RPA) is used assuming the existence of a Chirikov-like criterion for the onset of wave stochasticity. The dynamical amplitudes are represented as complex numbers, $\psi = \psi_r + i\psi_i = ae^{i\theta}$, with the amplitudes slowly varying whereas the phases are rapidly varying and, in particular, distributed uniformly over the interval $[0;2\pi)$. However, one could expect that the phase dynamics can play a role in the self-organisation and the formation of coherent structures. In the same manner it is also expected that the RPA falls short to take coherent interaction between phases into account. In this work therefore, we studied the role of phase dynamics and the coupling of phases between different modes on the characteristic time evolution of the turbulent. We assume a simple turbulent system where the so-called stochastic oscillator model can be employed. The idea of interpreting turbulence by stochastic oscillators. The stochastic oscillator models can be derived from radical simplifications of the nonlinear terms in the Navier-Stokes or Gyro-Kinetic equations. In this particular case we adopt the basic equation for the stochastic oscillator model with passive advection and random forcing from Ref.Comment: Proceedings of the 43rd EPS Conference on Plasma Physics, July 4-8, Leuven, Belgium 201

Self-organisation of random oscillators with L\'evy stable distributions

A novel possibility of self-organized behaviour of stochastically driven oscillators is presented. It is shown that synchronization by L\'evy stable processes is significantly more efficient than that by oscillators with Gaussian statistics. The impact of outlier events from the tail of the distribution function was examined by artificially introducing a few additional oscillators with very strong coupling strengths and it is found that remarkably even one such rare and extreme event may govern the long term behaviour of the coupled system. In addition to the multiplicative noise component, we have investigated the impact of an external additive L\'evy distributed noise component on the synchronisation properties of the oscillators.Comment: Accepted in J. Phys. A: Math. Theor. (2017

Non-Linear Langevin and Fractional Fokker-Planck Equations for Anomalous Diffusion by Levy Stable Processes

The~numerical solutions to a non-linear Fractional Fokker--Planck (FFP) equation are studied estimating the generalized diffusion coefficients. The~aim is to model anomalous diffusion using an FFP description with fractional velocity derivatives and Langevin dynamics where L\'{e}vy fluctuations are introduced to model the effect of non-local transport due to fractional diffusion in velocity space. Distribution functions are found using numerical means for varying degrees of fractionality of the stable L\'{e}vy distribution as solutions to the FFP equation. The~statistical properties of the distribution functions are assessed by a generalized normalized expectation measure and entropy and modified transport coefficient. The~transport coefficient significantly increases with decreasing fractality which is corroborated by analysis of experimental data.Comment: 20 pages 7 figure

Non-local gyrokinetic model of linear ion-temperature-gradient modes

A theory of non-local linear ion-temperature-gradient (ITG) drift modes while retaining non-adiabatic electrons is presented, extending the previous work [S. Moradi, et al {\em Phys. Plasmas} {\bf 18}, 062106 (2011)]. A dispersion relation is derived to quantify the effects of the fractional velocity operator in the Fokker-Planck equation modified by temperature gradients and non-adiabatic electrons on the real frequency and growth rate. Solving the dispersion relation, it is shown here that as the plasma becomes more turbulent, it deviates from a Maxwellian distribution and becomes L\'{e}vy distributed. The resulting L\'{e}vy distribution of the plasma may thus significantly alter the transport. The relative effect of the fractional derivative is larger on the real frequency than on the growth rate of the ITG mode.Comment: 14pages 1 Figure submitted to Phys. Rev.

Homer’s the Odyssey and Taskin-e-Shirazi’s Falaknaz Nameh: A Comparative Study of the Role of Women

The book Falak Naz Nameh is among the love-epic couplets and one of the lyrical works of the Persian Literature in the thirteenth century AH which shares some similar epical features with European romance and was said by a poet of Arab descent named Yaqub ibn Masud with the pen name of Taskin-e-Shirazi. The present inquiry has a comparative look at the aforementioned book and the epic written by Homer (the blind Greek poet) and compares and contrasts women in both epic books. Through a profound view, the similarities and differences of the two foregoing poets with regard to women were investigated and scrutinized. In both stories, the presence and participation of women are among the main focuses and some or all part of the epics are based on their roles and activities; moreover, the logical and reasonable procedure of the story are taken by them. Therefore, the topic of woman and the part she plays are among significant features in both epopees, for women are the causes of the establishment and continuation of what happens in the two stories

The role of phase dynamics in a stochastic model of a passively advected scalar

Collective synchronous motion of the phases is introduced in a model for the stochastic passive advection-diffusion of a scalar with external forcing. The model for the phase coupling dynamics follows the well known Kuramoto model paradigm of limit-cycle oscillators. The natural frequencies in the Kuramoto model are assumed to obey a given scale dependence through a dispersion relation of the drift-wave form $-\beta\frac{k}{1+k^2}$, where $\beta$ is a constant representing the typical strength of the gradient. The present aim is to study the importance of collective phase dynamics on the characteristic time evolution of the fluctuation energy and the formation of coherent structures. Our results show that the assumption of a fully stochastic phase state of turbulence is more relevant for high values of $\beta$, where we find that the energy spectrum follows a $k^{-7/2}$ scaling. Whereas for lower $\beta$ there is a significant difference between a-synchronised and synchronised phase states, and one could expect the formation of coherent modulations in the latter case.Comment: Accepted for publication in Physics of Plasma

Charged particle dynamics in the presence of non-Gaussian L\'evy electrostatic fluctuations

Full orbit dynamics of charged particles in a $3$-dimensional helical magnetic field in the presence of $\alpha$-stable L\'evy electrostatic fluctuations and linear friction modeling collisional Coulomb drag is studied via Monte Carlo numerical simulations. The L\'evy fluctuations are introduced to model the effect of non-local transport due to fractional diffusion in velocity space resulting from intermittent electrostatic turbulence. The probability distribution functions of energy, particle displacements, and Larmor radii are computed and showed to exhibit a transition from exponential decay, in the case of Gaussian fluctuations, to power law decay in the case of L\'evy fluctuations. The absolute value of the power law decay exponents are linearly proportional to the L\'evy index $\alpha$. The observed anomalous non-Gaussian statistics of the particles' Larmor radii (resulting from outlier transport events) indicate that, when electrostatic turbulent fluctuations exhibit non-Gaussian L\'evy statistics, gyro-averaging and guiding centre approximations might face limitations and full particle orbit effects should be taken into account.Comment: 5 pages, 5 figures. Accepted as a letter in Physics of Plasma

An Analysis of the Link between Metacognitive Beliefs and Academic Health-oriented Lifestyle Preventive Behaviours Mediated by Self-efficacy during the COVID-19 Pandemic

[EN] The outbreak of the coronavirus and its ramifications, including lockdown and shutting down of many learning centers magnified the necessity of turning to virtual learning, has given rise to concerns about students learning and their reaction to the new teaching methods and the challenges they entail. The present study attempts to examine the link between metacognitive beliefs and behaviors that prevent health-oriented lifestyles through academic self-efficacy during the COVID-19 pandemic. The statistical sample consisted of 239 randomly selected undergraduate students of engineering at Azad University of Shahre-e Rey in the second semester of 1399-1400. The data were gathered using academic health-oriented life style test Salehzadeh et al. (2018) Academic Self-Efficacy Beliefs Questionnaire (ASEBQ), and Wells Metacognition Questionnaire-30 (MCQ-30). Findings of the study indicated that metacognitive beliefs are related to behaviors preventing academic health-oriented life style factors, such as learned helplessness and effort withdrawal, through self-efficacy. It is suggested that, According to the positive relationship that exists between metacognitive strategies and academic achievement. As well as these strategies are scalability learners need to be trained in skills such as self-regulation self- monitoring planning and goal setting. Until they dominate decided cognitive strategies and professors can also encourage students to use orientation by designing assignments, teaching study strategies, and using new teaching methods.Moradi, F.; Aghaei Sabet, S.; Soufi, S. (2022). An Analysis of the Link between Metacognitive Beliefs and Academic Health-oriented Lifestyle Preventive Behaviours Mediated by Self-efficacy during the COVID-19 Pandemic. Multidisciplinary Journal for Education, Social and Technological Sciences. 9(1):39-58. https://doi.org/10.4995/muse.2022.1687939589