Estimation of interrelation between chaotic observables

Čenys, Antanas; Lasiene, G.; Pyragas, K.

doi:10.1016/0167-2789(91)90130-2

Cited by 51 publications

(30 citation statements)

References 11 publications

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“…Our study did not address issues concerning unclear cause of death, or how the cause was determined or who determined it. Second, the Finnish statistics do not [34], might be used to overcome this limitation. However, non-linear dependences were beyond the scope of this study.…”

Section: Discussionmentioning

confidence: 99%

Variation and seasonal patterns of suicide mortality in Finland and Sweden since the 1750s

Holopainen

Helama²,

Björkenstam³

et al. 2013

Environ Health Prev Med

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Objectives Suicide mortality varies in both the short and long term. Our study examines suicide mortality in Finland and Sweden from the 1750s until today. The aim of our study is to detect any seasonal peaks in suicide rates and examine their temporal evolution to suggest a mechanism that may explain such peaks. Method We acquired the study material from the Finnish and Swedish cause of death statistics (257,341 deaths by suicide) and the relevant population gender structure data. We then separately calculated the annual male and female suicide rates per 100,000 inhabitants. We analysed the suicide peaks, calculating factors of proportionality for the available data by dividing the suicide rates in the peak months (May and October) by the annual suicide rates. Results Suicide rates in Finland and Sweden peak twice a year. Both men and women in both countries most often commit suicide in May. There is another peak in October, with the exception of Finnish men. These suicide peaks coincide with a temperature increase in May and the biggest annual drop in temperature in October. We also observed a monotonic long-term change in the Swedish statistics, but not in the Finnish data. Our hypothesis is that seasonal variation in suicide rates may be caused by abrupt temperature changes twice a year that trigger the activity in brown adipose tissue and deepen depression. Conclusion While the overall suicide mortality rates varied considerably, the monthly proportions in May did not. This finding suggests a routine factor underlying the spring peak in suicide mortality.

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Section: Discussionmentioning

confidence: 99%

Variation and seasonal patterns of suicide mortality in Finland and Sweden since the 1750s

Holopainen

Helama²,

Björkenstam³

et al. 2013

Environ Health Prev Med

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“…It is not assumed that a meaningful instantaneous phase can be extracted from the signals. Under these assumptions, directional couplings can in principle be detected by quantifying the probability with which close states of the driven dynamics are mapped to close states of the driving dynamics [8,9,13,14].…”

Section: Introductionmentioning

confidence: 99%

Reliable detection of directional couplings using rank statistics

2009

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To detect directional couplings from time series various measures based on distances in reconstructed state spaces were introduced. These measures can, however, be biased by asymmetries in the dynamics' structure, noise color, or noise level, which are ubiquitous in experimental signals. Using theoretical reasoning and results from model systems we identify the various sources of bias and show that most of them can be eliminated by an appropriate normalization. We furthermore diminish the remaining biases by introducing a measure based on ranks of distances. This rank-based measure outperforms existing distance-based measures concerning both sensitivity and specificity for directional couplings. Therefore, our findings are relevant for a reliable detection of directional couplings from experimental signals.

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“…The detection of causality from a time series is an intensively developing technique (Granger, 1988;Čenys, Lasiene and Pyragas, 1991;Sugihara et al, 2012;Ma, Aihara and Chen, 2014;van Nes et al, 2015) The CD method utilizes one observable (e.g. sunspot area) of an unknown dynamical system (e.g.…”

Section: Causality Detection Methodsmentioning

confidence: 99%

“…Primary testing of the CD method was performed by Čenys, Lasiene and Pyragas (1991) for coupled Hennon maps and these results were reproduced by Volobuev and Makarenko (2016). The coupled Hennon map is a classical chaotic system, but it does not reproduce any feature of solar activity so we try to use here the Van der Pol system as a test system.…”

Section: Causality Detection For Model Systemsmentioning

confidence: 99%

Long-Term Pulses of Dynamic Coupling Between Solar Hemispheres

Volobuev

Makarenko

2017

Sol Phys

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North-south (N-S) asymmetry of solar activity is a known statistical phenomenon but its significance is difficult to prove or theoretically explain. Here we consider each solar hemisphere as a separate dynamical system connected with the other hemisphere via an unknown coupling parameter. We use a non-linear dynamics approach to calculate the scale-dependent conditional dispersion (CD) of sunspots between hemispheres. Using daily Greenwich sunspot areas, we calculated the Neumann and Pearson chi-squared distances between CDs as indices showing the direction of coupling. We introduce an additional index of synchronization which shows the strength of coupling and allows us to discriminate between complete synchronization and independency of hemispheres. All indices are evaluated in a four-year moving window showing the evolution of coupling between hemispheres. We find that the driver-response interrelation changes between hemispheres have a few pulses during 130 years of Greenwich data with an at least 40 years-long period of unidirectional coupling. These sharp nearly simultaneous pulses of all causality indices are found at the decay of some 11-year cycles. The pulse rate of this new phenomenon of dynamic coupling is irregular: although the first two pulses repeat after 22-year Hale cycles, the last two pulses repeat after three and four 11-year cycles respectively. The last pulse occurs at the decay phase of Cycle 23 so the next pulse will likely appear during the decay of future Cycle 25 or later. This new phenomenon of dynamic coupling reveals additional constraints for understanding and modeling of the long-term solar activity cycles.

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Estimation of interrelation between chaotic observables

Cited by 51 publications

References 11 publications

Variation and seasonal patterns of suicide mortality in Finland and Sweden since the 1750s

Variation and seasonal patterns of suicide mortality in Finland and Sweden since the 1750s

Reliable detection of directional couplings using rank statistics

Long-Term Pulses of Dynamic Coupling Between Solar Hemispheres

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