scholarly journals Scaling and singularity characteristics of solar wind and magnetospheric fluctuations

2002 ◽  
Vol 9 (2) ◽  
pp. 149-162 ◽  
Author(s):  
Z. Vörös ◽  
D. Jankovičová ◽  
P. Kovács
Keyword(s):  
Solar Wind ◽  
Magnetic Data ◽  
Data Sets ◽  
Magnetic Fluctuations ◽  
Mhd Turbulence ◽  
Magnetic Turbulence ◽  
Self Organized ◽  
Interaction Processes ◽  
Ae Index ◽  
Self Organized Criticality

Abstract. Preliminary results are presented which suggest that scaling and singularity characteristics of solar wind and ground-based magnetic fluctuations appear to be a significant component in the solar wind-magnetosphere interaction processes. Of key importance is the intermittence of the "magnetic turbulence" as seen in ground-based and solar wind magnetic data. The methods used in this paper (estimation of flatness and multifractal spectra) are commonly used in the studies of fluid or MHD turbulence. The results show that single observatory characteristics of magnetic fluctuations are different from those of the multi-observatory AE-index. In both data sets, however, the influence of the solar wind fluctuations is recognizable. The correlation between the scaling/singularity features of solar wind magnetic fluctuations and the corresponding geomagnetic response is demonstrated in a number of cases. The results are also discussed in terms of patchy reconnection processes in the magnetopause and forced and/or self-organized criticality (F/SOC) of internal magnetosphere dynamics.

scholarly journals Low frequency 1/<i>f</i>-like fluctuations of the AE-index as a possible manifestation of self-organized criticality in the magnetosphere

1998 ◽  
Vol 16 (12) ◽  
pp. 1580-1588 ◽  
Author(s):  
V. M. Uritsky ◽  
M. I. Pudovkin
Keyword(s):  
Solar Wind ◽  
Power Spectrum ◽  
Low Frequency ◽  
Solar Wind Plasma ◽  
Mhd Waves ◽  
Current Layer ◽  
Sandpile Model ◽  
Self Organized ◽  
Ae Index ◽  
Self Organized Criticality

Abstract. Low frequency stochastic variations of the geomagnetic AE-index characterized by 1/f b-like power spectrum (where f is a frequency) are studied. Based on the analysis of experimental data we show that the Bz-component of IMF, velocity of solar wind plasma, and the coupling function of Akasofu are insufficient factors to explain these behaviors of the AE-index together with the 1/f b fluctuations of geomagnetic intensity. The effect of self-organized criticality (SOC) is proposed as an internal mechanism to generate 1/f b fluctuations in the magnetosphere. It is suggested that localized spatially current instabilities, developing in the magnetospheric tail at the initial substorm phase can be considered as SOC avalanches or dynamic clusters, superposition of which leads to the 1/f b fluctuations of macroscopic characteristics in the system. Using the sandpile model of SOC, we undertake numerical modeling of space-localized and global disturbances of magnetospheric current layer. Qualitative conformity between the disturbed dynamics of self-organized critical state of the model and the main phases of real magnetospheric substorm development is demonstrated. It is also shown that power spectrum of sandpile model fluctuations controlled by real solar wind parameters reproduces all distinctive spectral features of the AE fluctuations.Key words. Magnetospheric physics (MHD waves and instabilities; solar wind · magnetosphere interactions; storms and substroms).

scholarly journals On the probability distribution function of small-scale interplanetary magnetic field fluctuations

2004 ◽  
Vol 22 (10) ◽  
pp. 3751-3769 ◽  
Author(s):  
R. Bruno ◽  
V. Carbone ◽  
L. Primavera ◽  
F. Malara ◽  
L. Sorriso-Valvo ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Robust Statistics ◽  
Interplanetary Space ◽  
Parametric Instability ◽  
Field Vector ◽  
Small Scale ◽  
Magnetic Fluctuations ◽  
Mhd Turbulence ◽  
The One

Abstract. In spite of a large number of papers dedicated to the study of MHD turbulence in the solar wind there are still some simple questions which have never been sufficiently addressed, such as: a) Do we really know how the magnetic field vector orientation fluctuates in space? b) What are the statistics followed by the orientation of the vector itself? c) Do the statistics change as the wind expands into the interplanetary space? A better understanding of these points can help us to better characterize the nature of interplanetary fluctuations and can provide useful hints to investigators who try to numerically simulate MHD turbulence. This work follows a recent paper presented by some of the authors which shows that these fluctuations might resemble a sort of random walk governed by Truncated Lévy Flight statistics. However, the limited statistics used in that paper did not allow for final conclusions but only speculative hypotheses. In this work we aim to address the same problem using more robust statistics which, on the one hand, forces us not to consider velocity fluctuations but, on the other hand, allows us to establish the nature of the governing statistics of magnetic fluctuations with more confidence. In addition, we show how features similar to those found in the present statistical analysis for the fast speed streams of solar wind are qualitatively recovered in numerical simulations of the parametric instability. This might offer an alternative viewpoint for interpreting the questions raised above.

scholarly journals Solar cycle dependence of scaling in solar wind fluctuations

2008 ◽  
Vol 15 (3) ◽  
pp. 445-455 ◽  
Author(s):  
S. C. Chapman ◽  
B. Hnat ◽  
K. Kiyani
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Momentum Flux ◽  
Magnetic Fluctuations ◽  
Mhd Turbulence ◽  
Scaling Properties ◽  
Two Component ◽  
Energy And Momentum ◽  
Cycle Dependence

Abstract. In this review we collate recent results for the statistical scaling properties of fluctuations in the solar wind with a view to synthesizing two descriptions: that of evolving MHD turbulence and that of a scaling signature of coronal origin that passively propagates with the solar wind. The scenario that emerges is that of coexistent signatures which map onto the well known "two component" picture of solar wind magnetic fluctuations. This highlights the need to consider quantities which track Alfvénic fluctuations, and energy and momentum flux densities to obtain a complete description of solar wind fluctuations.

scholarly journals Emergence of intermittent structures and reconnection in MHD turbulence

2010 ◽  
Vol 6 (S274) ◽  
pp. 116-119
Author(s):  
Antonella Greco ◽  
Sergio Servidio ◽  
William H. Matthaeus ◽  
Pablo Dmitruk
Keyword(s):  
Numerical Simulation ◽  
Solar Wind ◽  
Magnetic Reconnection ◽  
Numerical Algorithms ◽  
Magnetic Fluctuations ◽  
Mhd Turbulence ◽  
Local Origin ◽  
Tangential Discontinuities

AbstractIn recent analyses of numerical simulation and solar wind dataset, the idea that the magnetic discontinuities may be related to intermittent structures that appear spontaneously in MHD turbulence has been explored in details. These studies are consistent with the hypothesis that discontinuity events founds in the solar wind might be of local origin as well, i.e. a by-product of the turbulent evolution of magnetic fluctuations.Using simulations of 2D MHD turbulence, we are exploring a possible link between tangential discontinuities and magnetic reconnection. The goal is to develop numerical algorithms that may be useful for solar wind applications.

STATISTICAL PROPERTIES OF SOLAR FLARES AND COMPARISON TO OTHER IMPULSIVE ENERGY RELEASE EVENTS

2009 ◽  
Vol 23 (28n29) ◽  
pp. 5609-5618 ◽  
Author(s):  
FABIO LEPRETI ◽  
VLADIMIR G. KOSSOBOKOV ◽  
VINCENZO CARBONE
Keyword(s):  
Solar Flare ◽  
Energy Release ◽  
Solar Flares ◽  
Statistical Properties ◽  
Universal Curve ◽  
Mhd Turbulence ◽  
Natural Systems ◽  
Self Organized ◽  
Self Organized Criticality ◽  
Impulsive Processes

Impulsive energy release events are observed in many natural systems. Solar flares are certainly among the most remarkable examples of such processes. In the last years the study of solar flare statistical properties has received considerable attention in the context of solar flare models based on different approaches, such as Self Organized Criticality (SOC) or magnetohydrodynamic (MHD) turbulence. In this talk the main statistical properties of solar flares will be presented and compared to those of other well known impulsive processes, such as earthquakes and soft γ-ray flashes occurring on neutron stars. It is shown that the these phenomena are characterized by different statistics that cannot be rescaled onto a single, universal curve and that this holds even for the same phenomenon, when observed in different periods or at different locations. Our results indicate apparent complexity of impulsive energy release processes, which neither follow a common behavior nor could be attributed to a universal physical mechanism.

scholarly journals Auroral precipitation fading before and at substorm onset: ionospheric and geostationary signatures

1997 ◽  
Vol 15 (8) ◽  
pp. 967-983 ◽  
Author(s):  
K. Kauristie ◽  
T. I. Pulkkinen ◽  
A. Huuskonen ◽  
R. J. Pellinen ◽  
H. J. Opgenoorth ◽  
...  
Keyword(s):  
Solar Wind ◽  
Electron Flux ◽  
Plasma Pressure ◽  
Substorm Onset ◽  
Magnetic Data ◽  
Continuous Energy ◽  
Ae Index ◽  
Before And After ◽  
Fading Effect ◽  
Spatio Temporal

Abstract. Rapid fading of auroral activity a few minutes before substorm breakup has earlier been analyzed in case-studies. Here we report on a study in which all-sky camera (ASC) and magnetic data over 3 years were examined to find breakups that were accompanied by a preceding fading. To illustrate typical features of the fading effect we analyze three events in detail and discuss seven other events to find the spatial and temporal behavior of the fading and the global conditions favoring this phenomenon, which is not associated with every breakup. In these ten events the precipitation diminished typically for about 2 min and a local breakup followed after 2–3 min. Usually the arc which broke up had faded earlier. Comparison with geostationary electron flux recordings shows that in many cases the global onset had already taken place when the fading was recorded at a different longitude. Thus fading is not just a growth-phase phenomenon as often thought, but can also appear as a precursor of the approaching auroral bulge. The AE index and solar-wind data reveal that the fading has a tendency to take place during magnetically disturbed conditions caused by continuous energy input from the solar wind. Furthermore, while a widely recognized phenomenon, we have found that the fading prior to breakup is not a very common feature in the spatio-temporal scale of auroral ASC recordings. In many cases the deepness of the fading had a longitudinal dependence, which leads to the suggestion that this phenomenon is related to azimuthal gradients in the tail magnetic field and/or plasma pressure. Possible scenarios causing fading both before and after the onset are discussed based on a few previously presented theoretical auroral-arc models.

scholarly journals From pre-storm activity to magnetic storms: a transition described in terms of fractal dynamics

2006 ◽  
Vol 24 (12) ◽  
pp. 3557-3567 ◽  
Author(s):  
G. Balasis ◽  
I. A. Daglis ◽  
P. Kapiris ◽  
M. Mandea ◽  
D. Vassiliadis ◽  
...  
Keyword(s):  
Solar Wind ◽  
Magnetic Storm ◽  
General Character ◽  
Critical Feature ◽  
Storm Activity ◽  
Dst Index ◽  
Self Organized ◽  
Main Driver ◽  
Scaling Parameters ◽  
Self Organized Criticality

Abstract. We show that distinct changes in scaling parameters of the Dst index time series occur as an intense magnetic storm approaches, revealing a gradual reduction in complexity. The remarkable acceleration of energy release – manifested in the increase in susceptibility – couples to the transition from anti-persistent (negative feedback) to persistent (positive feedback) behavior and indicates that the occurence of an intense magnetic storm is imminent. The main driver of the Dst index, the VBSouth electric field component, does not reveal a similar transition to persistency prior to the storm. This indicates that while the magnetosphere is mostly driven by the solar wind the critical feature of persistency in the magnetosphere is the result of a combination of solar wind and internal magnetospheric activity rather than solar wind variations alone. Our results suggest that the development of an intense magnetic storm can be studied in terms of "intermittent criticality" that is of a more general character than the classical self-organized criticality phenomena, implying the predictability of the magnetosphere.

scholarly journals Do the solar flares originating from an individual active region follow a random process or a memory-dependent correlation?

2020 ◽  
Vol 494 (1) ◽  
pp. 975-982
Author(s):  
W H Lei ◽  
C Li ◽  
F Chen ◽  
S J Zhong ◽  
Z G Xu ◽  
...  
Keyword(s):  
Active Region ◽  
Random Process ◽  
Waiting Time ◽  
Solar Flares ◽  
Three Dimensional ◽  
Mhd Turbulence ◽  
Self Organized ◽  
Self Organized Criticality ◽  
Cycle 24 ◽  
Non Linear System

ABSTRACT We investigate the waiting time statistics of solar flares both in a flare-productive active region (AR 12673) of the solar cycle 24 and in a three-dimensional magnetohydrodynamic (MHD) simulated AR. The statistical models of a discrete random process and a continuous memory-dependent process are applied to interpret the waiting time distributions (WTDs) of solar flares. Our results indicate that the occurrence of a solar flare in an individual AR maintains a certain amount of memory, and probably arises from MHD turbulence rather than from intermittent avalanches in a self-organized criticality system. It differs from the occurrence of ‘super flares’ when treating the star/Sun as a single non-linear system.

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