2021/04/14 by Belén Acosta, Acosta, Belén, Denisse Pastén +4 · 1 citation
Economics, Econometrics and Finance · Computer Science · Physics and Astronomy · #Complex Systems and Time Series Analysis #Time Series Analysis and Forecasting #Statistical Mechanics and Entropy
paper · pdf · doi:10.48550/arxiv.2104.06623
One of the fundamental open questions in plasma physics is the role of\nnon-thermal particles distributions in poorly collisional plasma environments,\na system commonly found throughout the Universe, e.g. the solar wind and the\nEarth's magnetosphere correspond to natural plasma physics laboratories in\nwhich turbulent phenomena can be studied. Our study perspective is born from\nthe method of Horizontal Visibility Graph (HVG) that has been developed in the\nlast years to analyze time series avoiding the tedium and the high\ncomputational cost that other methods offer. Here we build a complex network\nbased on directed HVG technique applied to magnetic field fluctuations time\nseries obtained from Particle In Cell (PIC) simulations of a magnetized\ncollisionless plasma to distinguish the degree distributions and calculate the\nKullback-Leibler Divergence (KLD) as a measure of relative entropy of data sets\nproduced by processes that are not in equilibrium. First, we analyze the\nconnectivity probability distribution for the undirected version of HVG finding\nhow the Kappa distribution for low values of \κ tends to be an\nuncorrelated time series, while the Maxwell-Boltzmann distribution shows a\ncorrelated stochastic processes behavior. Then, we investigate the degree of\ntemporary irreversibility of magnetic fluctuations self-generated by the\nplasma, comparing the case of a thermal plasma (described by a Maxwell-Botzmann\nvelocity distribution function) with non-thermal Kappa distributions. We have\nshown that the KLD associated to the HVG is able to distinguish the level of\nreversibility associated to the thermal equilibrium in the plasma because the\ndissipative degree of the system increases as the value of \κ parameter\ndecreases and the distribution function departs from the Maxwell-Boltzmann\nequilibrium.\n