Self-organized Criticality in Compact Plasmas

Sivron, R.

doi:10.1086/311516

Cited by 7 publications

(4 citation statements)

References 39 publications

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“…Statistics of the fluctuations in the light curve from Cygnus X-1, observed in hard X-rays with Ginga and Chandra, exhibit complex 1/f noise spectra and size distributions of peak fluxes with very steep powerlaw slopes of α P ≈ 7.1 Mineshige and Negoro 1999), which have been interpreted in terms of SOC models applied to accretion disks (Mineshige et al 1994a,b;Takeuchi et al 1995;Mineshige and Negoro 1999). A SOC interpretation was also suggested for the VY Scl-type cataclysmic variable KR Aurigae (Kato et al 2002;Dobrotka et al 2012), UU Aqr (Dobrotka et al 2012), and for the broad-line radio galaxy 3C-390.3 (Leighly and O'Brien 1997), for the Seyfert I MCG- 6-30-15 (Sivron and Goralski 1998;Sivron 1998), or for the extreme narrow-line Seyfert 1 galaxy IRAS 13224-3909 (Gaskell 2004), which all exhibit a highly intermittent variability on top of a shot noise background like Cygnus X-1.…”

Section: Black Holes and Accretion Disksmentioning

confidence: 96%

25 Years of Self-Organized Criticality: Solar and Astrophysics

et al. 2014

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Shortly after the seminal paper "Self-Organized Criticality: An explanation of 1/f noise" by Bak et al. (1987), the idea has been applied to solar physics, in "Avalanches and the Distribution of Solar Flares" by Lu and Hamilton (1991). In the following years, an inspiring cross-fertilization from complexity theory to solar and astrophysics took place, where the SOC concept was initially applied to solar flares, stellar flares, and magnetospheric substorms, and later extended to the radiation belt, the heliosphere, lunar craters, the asteroid belt, the Saturn ring, pulsar glitches, soft X-ray repeaters, blazars, black-hole objects, cosmic rays, and boson clouds. The application of SOC concepts has been performed by numerical cellular automaton simulations, by analytical calculations of statistical (powerlaw-like) distributions based on physical scaling laws, and by observational tests of theoretically predicted size distributions and waiting time distributions. Attempts have been undertaken to import physical models into the numerical SOC toy models, such as the discretization of magneto-hydrodynamics (MHD) processes. The novel applications stimulated also vigorous debates about the discrimination between SOC models, SOC-like, and non-SOC processes, such as phase transitions, turbulence, random-walk diffusion, percolation, branching processes, network theory, chaos theory, fractality, multi-scale, and other complexity phenomena. We review SOC studies from the last 25 years and highlight new trends, open questions, and future challenges, as discussed during two recent ISSI workshops on this theme

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Section: Black Holes and Accretion Disksmentioning

confidence: 96%

25 Years of Self-Organized Criticality: Solar and Astrophysics

et al. 2014

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“…Applications to solar flares have been given by Lu and Hamilton (1991) and Lu et al (1993) and to accretionary discs by Dendy et al (1998). Applications to plasma physics have been given by Carreras et al (1996), Kishimoto et al (1996), Medvedev et al (1996), Sivron (1998), andRhodes et al (1999). Field et al (1995), Zieve et al (1996), Olson et al (1997), Bassler andPaczuski (1998), andProzorov andGiller (1999) have considered vortex avalanches in super-conductors.…”

Section: Other Applications In the Physical Sciencesmentioning

confidence: 99%

Self-organized criticality

1999

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The concept of self-organized criticality was introduced to explain the behaviour of the sandpile model. In this model, particles are randomly dropped onto a square grid of boxes. When a box accumulates four particles they are redistributed to the four adjacent boxes or lost off the edge of the grid. Redistributions can lead to further instabilities with the possibility of more particles being lost from the grid, contributing to the size of each 'avalanche'. These model 'avalanches' satisfied a power-law frequency-area distribution with a slope near unity. Other cellular-automata models, including the slider-block and forest-fire models, are also said to exhibit self-organized critical behaviour. It has been argued that earthquakes, landslides, forest fires, and species extinctions are examples of self-organized criticality in nature. In addition, wars and stock market crashes have been associated with this behaviour. The forest-fire model is particularly interesting in terms of its relation to the critical-point behaviour of the sitepercolation model. In the basic forest-fire model, trees are randomly planted on a grid of points. Periodically in time, sparks are randomly dropped on the grid. If a spark drops on a tree, that tree and adjacent trees burn in a model fire. The fires are the 'avalanches' and they are found to satisfy power-law frequency-area distributions with slopes near unity. This forest-fire model is closely related to the site-percolation model, that exhibits critical behaviour. In the forest-fire model there is an inverse cascade of trees from small clusters to large clusters, trees are lost primarily from model fires that destroy the largest clusters. This quasi steady-state cascade gives a power-law frequency-area distribution for both clusters of trees and smaller fires. The site-percolation model is equivalent to the forest-fire model without fires. In this case there is a transient cascade of trees from small to large clusters and a power-law distribution is found only at a critical density of trees.

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“…If the optical emission correlates to the released energy of the avalanches, this model results in a red noise light curve. A more general motivation on SOC in BL Lac objects is given by the models of SOC in compact plasmas (Sivron 1998) and astronomical shocks (Malkov et al 2000). At long time scales the effect of SOC may be limited by the effective size of the emitting region.…”

Section: Introductionmentioning

confidence: 99%

Long-term optical variability of PKS 2155-304

Kastendieck

Ashley

Horns

2011

A&A

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Aims. The optical variability of the blazar PKS 2155-304 is investigated to characterise the red noise behaviour at largely different time scales from 20 days to O(>10 yrs). Methods. The long-term optical light curve of PKS 2155-304 is assembled from archival data as well as from so-far unpublished observations mostly carried out with the ROTSE-III and the ASAS robotic telescopes. A forward folding technique is used to determine the best-fit parameters for a model of a power law with a break in the power spectral density function (PSD). The best-fit parameters are estimated using a maximum-likelihood method with simulated light curves in conjunction with the Lomb-Scargle periodogram and the first-order structure function (SF). In addition, a new approach based upon the so-called multiple fragments variance function (MFVF) is introduced and compared to the other methods. Simulated light curves have been used to confirm the reliability of these methods as well as to estimate the uncertainties of the best-fit parameters. Results. The light curve is consistent with the assumed broken power-law PSD. All three methods agree within the estimated uncertainties with the MFVF providing the most accurate results. The red-noise behaviour of the PSD in frequency f follows a power law with f −β , β = 1.8 +0.1 −0.2 and a break towards f 0 at frequencies lower than f min = (2.7 +2.2 −1.6 yrs) −1 .

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Self-organized Criticality in Compact Plasmas

Cited by 7 publications

References 39 publications

25 Years of Self-Organized Criticality: Solar and Astrophysics

25 Years of Self-Organized Criticality: Solar and Astrophysics

Self-organized criticality

Long-term optical variability of PKS 2155-304

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