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 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.

Foreshock ULF fluctuations near the Moon: THEMIS observations

2021 ◽  
Author(s):  
Anna Salohub ◽  
Jana Šafránková ◽  
Zdeněk Němeček
Keyword(s):  
Solar Wind ◽  
Rest Frame ◽  
Low Frequency ◽  
Solar Wind Plasma ◽  
Turbulent Plasma ◽  
Bow Shock ◽  
Ulf Waves ◽  
The Moon ◽  
Shock Surface ◽  
The Earth

&lt;p&gt;The foreshock is a region filled with a turbulent plasma located upstream the Earth&amp;#8217;s bow shock where interplanetary magnetic field (IMF) lines are connected to the bow shock surface. In this region, ultra-low frequency (ULF) waves are generated due to the interaction of the solar wind plasma with particles reflected from the bow shock back into the solar wind. It is assumed that excited waves grow and they are convected through the solar wind/foreshock, thus the inner spacecraft (close to the bow shock) would observe larger wave amplitudes than the outer (far from the bow shock) spacecraft. The paper presents a statistical analysis of excited ULF fluctuations observed simultaneously by two closely separated THEMIS spacecraft orbiting the Moon under a nearly radial IMF. We found that ULF fluctuations (in the plasma rest frame) can be characterized as a mixture of transverse and compressional modes with different properties at both locations. We discuss the growth and/or damping of ULF waves during their propagation.&lt;/p&gt;

SELF-ORGANIZED CRITICALITY IN AN ASEXUAL MODEL?

2000 ◽  
Vol 11 (06) ◽  
pp. 1257-1262 ◽  
Author(s):  
COLIN CHISHOLM ◽  
NAEEM JAN ◽  
PETER GIBBS ◽  
AYŞE ERZAN
Keyword(s):  
Steady State ◽  
Recent Work ◽  
Critical Behavior ◽  
Critical State ◽  
Small Perturbations ◽  
Sandpile Model ◽  
Self Organized ◽  
Search For Self ◽  
Self Organized Criticality

Recent work has shown that the distribution of steady state mutations for an asexual "bacteria" model has features similar to that seen in Self-Organized Critical (SOC) sandpile model of Bak et al. We investigate this coincidence further and search for "self-organized critical" state for bacteria but instead find that the SOC sandpile critical behavior is very sensitive; critical behavior is destroyed with small perturbations effectively when the absorption of sand is introduced. It is only in the limit when the length of the genome of the bacteria tends to infinity that SOC properties are recovered for the asexual model.

scholarly journals Fractal analysis for the ULF data during the 1993 Guam earthquake to study prefracture criticality

2006 ◽  
Vol 13 (4) ◽  
pp. 409-412 ◽  
Author(s):  
Y. Ida ◽  
M. Hayakawa
Keyword(s):  
Fractal Analysis ◽  
Main Shock ◽  
Epicentral Distance ◽  
Sense Of Self ◽  
Low Frequency ◽  
Large Earthquake ◽  
Self Organized ◽  
Self Organized Criticality ◽  
Electromagnetic Signature

Abstract. An extremely large earthquake (with magnitude of 8.2) happened on 8 August 1993 near the Guam island, and ultra-low-frequency (ULF) (frequency less than 1 Hz) electromagnetic fields were measured by 3-axis induction magnetometers at an observing station (with the epicentral distance of 65 km) with sampling frequency of 1 Hz. In order to study electromagnetic signature of prefracture criticality, we have undertaken the fractal (mono-fractal) analysis by means of the Higuchi's method for the ULF data during the 1993 Guam earthquake. Then, it is found that the fractal dimension exhibits five maxima 99, 75, 52, 21, and 9–4 days before the earthquake main shock, which suggests the ULF electromagnetic signature of nonlinear evolution (in the sense of self-organized criticality) taking place in the lithosphere just before the 1993 large Guam earthquake. That is, there take place step-like changes in the lithosphere during the long-term of the order of several months before the main shock.

scholarly journals The RPW Low Frequency Receiver (LFR) on Solar Orbiter: in-situ LF electric and magnetic field measurements of the solar wind expansion

2020 ◽  
Author(s):  
Thomas Chust ◽  
Olivier Le Contel ◽  
Matthieu Berthomier ◽  
Alessandro Retinò ◽  
Fouad Sahraoui ◽  
...  
Keyword(s):  
Solar Wind ◽  
Low Frequency ◽  
Field Measurements ◽  
Solar Wind Plasma ◽  
Wind Condition ◽  
The Sun ◽  
Nasa Mission ◽  
Magnetic Field Measurements ◽  
Electric And Magnetic Field

&lt;p&gt;Solar Orbiter (SO) is an ESA/NASA mission for exploring the Sun-Heliosphere connection which has been launched in February 2020. The Low Frequency Receiver (LFR) is one of the main subsystems of the Radio and Plasma Wave (RPW) experiment on SO. It is designed for characterizing the low frequency (~0.1Hz&amp;#8211;10kHz) electromagnetic fields &amp; waves which develop, propagate, interact, and dissipate in the solar wind plasma. In correlation with particle observations it will help to understand the heating and acceleration processes at work during its expansion. We will present the first LFR data gathered during the Near Earth Commissioning Phase, and will compare them with MMS data recorded in similar solar wind condition.&lt;/p&gt;

Generation of magnetic and particle Pc5 pulsations during the recovery phase of strong magnetic storms

2010 ◽  
Vol 466 (2123) ◽  
pp. 3363-3390 ◽  
Author(s):  
V. Pilipenko ◽  
O. Kozyreva ◽  
V. Belakhovsky ◽  
M. J. Engebretson ◽  
S. Samsonov
Keyword(s):  
Solar Wind ◽  
Spatial Structure ◽  
Stable State ◽  
Low Frequency ◽  
Solar Wind Plasma ◽  
Recovery Phase ◽  
Magnetic Storms ◽  
Relativistic Electrons ◽  
Oscillatory Systems ◽  
Using Data

The dynamics of intense ultra-low-frequency (ULF) activity during three successive strong magnetic storms during 29–31 October 2003 are considered in detail. The spatial structure of Pc5 waves during the recovery phases of these storms is considered not only from the perspective of possible physical mechanisms, but as an important parameter of the ULF driver of relativistic electrons. The global structure of these disturbances is studied using data from a worldwide array of magnetometers and riometers augmented with data from particle detectors and magnetometers on board magnetospheric satellites (GOES, LANL). The local spatial structure is examined using the IMAGE magnetometers and Finnish riometer array. Though a general similarity between the quasi-periodic magnetic and riometer variations is observed, their local propagation patterns turn out to be different. To interpret the observations, we suggest a hypothesis of coupling between two oscillatory systems—a magnetospheric magnetohydrodynamic (MHD) waveguide/resonator and a system consisting of turbulence + electrons. We propose that the observed Pc5 oscillations are the result of MHD waveguide excitation along the dawn and dusk flanks of the magnetosphere. The magnetospheric waveguide turns out to be in a meta-stable state under high solar wind velocities, and quasi-periodic fluctuations of the solar wind plasma density stimulate the waveguide excitation.

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