Space storm as a phase transition

Wanliss, J. A.; Dobias, Peter

doi:10.1016/j.jastp.2007.01.001

Cited by 38 publications

(40 citation statements)

References 43 publications

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“…This transition is indicated by the change from β(t) < 2 prior to the storm onset and β(t) > 2 for some time after the onset. These observations are consistent with conclusions obtained by Alava (2003), Chang et al (2003Chang et al ( , 2004, Balasis et al (2006), and Wanliss and Dobias (2007). The obvious presence of fractal scaling behaviour at all times, and the variation in scaling exponents from quiet to active intervals, suggest that the non-equilibrium mag- Fig.…”

Section: Discussionsupporting

confidence: 91%

“…This result is in accordance with the entropy decrease shown by Balasis et al (2008Balasis et al ( , 2009. A transition from a random to a correlated state was actually observed and discussed during the active periods of storm in the Dst index and the SYM-H index (Wanliss, 2005a;Wanliss and Dobias, 2007).…”

Section: Discussionsupporting

confidence: 89%

“…Some previous works have demonstrated the statistical self-affinity properties observed in the geomagnetic times series (Chang, 1999;Sitnov et al, 2001;Uritsky et al, 2001Uritsky et al, , 2006Kovacs et al, 2001;Lui, 2002;Wanliss, 2005a;Balasis et al, 2006;Wanliss and Dobias, 2007).…”

Section: Introductionmentioning

confidence: 96%

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Wavelet-based multiscale analysis of geomagnetic disturbance

Zaourar¹,

Hamoudi²,

Mandéa

et al. 2013

Earth Planet Sp

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The dynamics of external contributions to the geomagnetic field is investigated by applying time-frequency methods to magnetic observatory data. Fractal models and multiscale analysis enable obtaining maximum quantitative information related to the short-term dynamics of the geomagnetic field activity. The stochastic properties of the horizontal component of the transient external field are determined by searching for scaling laws in the power spectra. The spectrum fits a power law with a scaling exponent β, a typical characteristic of self-affine time-series. Local variations in the power-law exponent are investigated by applying wavelet analysis to the same time-series. These analyses highlight the self-affine properties of geomagnetic perturbations and their persistence. Moreover, they show that the main phases of sudden storm disturbances are uniquely characterized by a scaling exponent varying between 1 and 3, possibly related to the energy contained in the external field. These new findings suggest the existence of a long-range dependence, the scaling exponent being an efficient indicator of geomagnetic activity and singularity detection. These results show that by using magnetogram regularity to reflect the magnetosphere activity, a theoretical analysis of the external geomagnetic field based on local power-law exponents is possible.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionsupporting

confidence: 89%

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Wavelet-based multiscale analysis of geomagnetic disturbance

Zaourar¹,

Hamoudi²,

Mandéa

et al. 2013

Earth Planet Sp

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“…It is known that the Earth's magnetospheric dynamics is characterized by persistent dynamic correlations (e.g., Dobias and Wanliss, 2009) and near-criticality dynamics (e.g., Consolini, 2002;Wanliss and Uritsky, 2010), which are correlated features in self-organized critical systems in stationary conditions also away from the critical point (Woodard et al, 2007). Furthermore, the persistent character of the magnetospheric dynamics has been shown to undergo dynamical changes during magnetic storms and substorms (e.g., Wanliss, 2005;Balasis et al, 2006;Wanliss and Dobias, 2007). These points suggest that the more complex observed relation between the multifractional nature and the intermittent character of the geomagnetic fluctuations (see, e.g., Figs.…”

Section: Discussionmentioning

confidence: 99%

“…It has been found that the fractal character of several geomagnetic time series, for example those relative to the geomagnetic indices AE, Dst and SYM-H, changes during magnetic storms and substorms (Uritsky and Pudovkin, 1998;Wanliss, 2005;Balasis et al, 2006;Wanliss and Dobias, 2007;Dobias and Wanliss, 2009). In particular, it has been noticed that the self-similarity properties of these time series change when an intense magnetospheric/geomagnetic activity event approaches.…”

Section: Introductionmentioning

confidence: 99%

Intermittency and multifractional Brownian character of geomagnetic time series

Consolini

Marco

Michelis

2013

Nonlin. Processes Geophys.

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The Earth's magnetosphere exhibits a complex behavior in response to the solar wind conditions. This behavior, which is described in terms of mutifractional Brownian motions, could be the consequence of the occurrence of dynamical phase transitions. On the other hand, it has been shown that the dynamics of the geomagnetic signals is also characterized by intermittency at the smallest temporal scales. Here, we focus on the existence of a possible relationship in the geomagnetic time series between the multifractional Brownian motion character and the occurrence of intermittency. In detail, we investigate the multifractional nature of two long time series of the horizontal intensity of the Earth's magnetic field as measured at L'Aquila Geomagnetic Observatory during two years (2001 and 2008), which correspond to different conditions of solar activity. We propose a possible double origin of the intermittent character of the small-scale magnetic field fluctuations, which is related to both the multifractional nature of the geomagnetic field and the intermittent character of the disturbance level. Our results suggest a more complex nature of the geomagnetic response to solar wind changes than previously thought

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On the local Hurst exponent of geomagnetic field fluctuations: Spatial distribution for different geomagnetic activity levels

Michelis

Consolini

2015

JGR Space Physics

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This study attempts to characterize the spatial distribution of the scaling features of the short time scale magnetic field fluctuations obtained from 45 ground-based geomagnetic observatories distributed in the Northern Hemisphere. We investigate the changes of the scaling properties of the geomagnetic field fluctuations by evaluating the local Hurst exponent and reconstruct maps of this index as a function of the geomagnetic activity level. These maps permit us to localize the different latitudinal structures responsible for disturbances and related to the ionospheric current systems. We find that the geomagnetic field fluctuations associated with the different ionospheric current systems have different scaling features, which can be evidenced by the local Hurst exponent. We also find that in general, the local Hurst exponent for quiet magnetospheric periods is higher than that for more active periods suggesting that the dynamical processes that are activated during disturbed times are responsible for changes in the nature of the geomagnetic field fluctuations.

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Space storm as a phase transition

Cited by 38 publications

References 43 publications

Wavelet-based multiscale analysis of geomagnetic disturbance

Wavelet-based multiscale analysis of geomagnetic disturbance

Intermittency and multifractional Brownian character of geomagnetic time series

On the local Hurst exponent of geomagnetic field fluctuations: Spatial distribution for different geomagnetic activity levels

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