Complexity and Intermittent Turbulence in Space Plasmas

Sporadic and localized interactions of coherent structures arising from plasma resonances can be the origin of "complexity" of the coexistence of non- propagating spatiotemporal fluctuations and propagating modes in space plasmas. Numerical simulation results are presented to demonstrate the intermittent character of the non-propagating fluctuations. The technique of the dynamic renormalization-group is introduced and applied to the study of scale invariance of such type of multiscale fluctuations. We also demonstrate that the particle interactions with the intermittent turbulence can lead to the efficient energization of the plasma populations. An example related to the ion acceleration processes in the auroral zone is provided

ROMA (Rank-Ordered Multifractal Analysis) for intermittent fluctuations with global crossover behavior

Rank-Ordered Multifractal Analysis (ROMA), a recently developed technique that combines the ideas of parametric rank ordering and one parameter scaling of monofractals, has the capabilities of deciphering the multifractal characteristics of intermittent fluctuations. The method allows one to understand the multifractal properties through rank-ordered scaling or non-scaling parametric variables. The idea of the ROMA technique is applied to analyze the multifractal characteristics of the auroral zone electric field fluctuations observed by SIERRA. The observed fluctuations span across contiguous multiple regimes of scales with different multifractal characteristics. We extend the ROMA technique such that it can take into account the crossover behavior -- with the possibility of collapsing probability distributions functions (PDFs) -- over these contiguous regimes.Comment: 24 pages, 18 figure

Active auroral arc powered by accelerated electrons from very high altitudes

オーロラ粒子の加速領域が超高高度まで広がっていたことを解明 －オーロラ粒子の加速の定説を覆す発見－. 京都大学プレスリリース. 2021-01-20.Bright, discrete, thin auroral arcs are a typical form of auroras in nightside polar regions. Their light is produced by magnetospheric electrons, accelerated downward to obtain energies of several kilo electron volts by a quasi-static electric field. These electrons collide with and excite thermosphere atoms to higher energy states at altitude of ~ 100 km; relaxation from these states produces the auroral light. The electric potential accelerating the aurora-producing electrons has been reported to lie immediately above the ionosphere, at a few altitudes of thousand kilometres1. However, the highest altitude at which the precipitating electron is accelerated by the parallel potential drop is still unclear. Here, we show that active auroral arcs are powered by electrons accelerated at altitudes reaching greater than 30, 000 km. We employ high-angular resolution electron observations achieved by the Arase satellite in the magnetosphere and optical observations of the aurora from a ground-based all-sky imager. Our observations of electron properties and dynamics resemble those of electron potential acceleration reported from low-altitude satellites except that the acceleration region is much higher than previously assumed. This shows that the dominant auroral acceleration region can extend far above a few thousand kilometres, well within the magnetospheric plasma proper, suggesting formation of the acceleration region by some unknown magnetospheric mechanisms

Magnetic field and energetic particle flux oscillations and high- frequency waves deep in the inner magnetosphere during substorm dipolarization: ERG observations

Using Exploration of energization and Radiation in Geospace (ERG or Arase) spacecraft data, we studied low-frequency magnetic field and energetic particle flux oscillations and high-frequency waves deep in the inner magnetosphere at a radial distance of ~4–5 during substorm dipolarization. The magnetic field oscillated alternately between dipole-like and taillike configuration at a period of 1 min during dipolarization. When the magnetic field was dipole-like, the parallel magnetic component of the Pi2 waves was at trough. Both energetic ion and electron fluxes with a few to tens of kiloelectronvolts enhanced out of phase, indicating that magnetosonic waves were in slow mode. Field-aligned currents also oscillated. These observations are consistent with signatures of ballooning instability. In addition, we found that broadband waves from the Pi1 range to above the electron cyclotron frequency tended to appear intermittently in the central plasma sheet near dipole-like configuration

Preface to the Special Issue on "Connection of Solar and Heliospheric Activities with Near-Earth Space Weather: Sun-Earth Connection"

This special issue of the Terrestrial, Atmospheric and Oceanic Sciences (TAO) presents a small collection of the materials presented at the 2011 International Space Plasma Symposium (ISPS), held at National Cheng-Kung University (NCKU) in Tainan, Taiwan, Republic of China (ROC), from August 15 - 19, 2011. The purpose of the Symposium was to bring space physicists together to present their recent research results and discuss some outstanding questions in, but not limited to, the solar corona, interplanetary medium, planetary magnetosphere and ionospheres. A total number of 59 papers were presented at the Symposium by scientists from 11 countries and regions

Renormalization-group study of a sandpile (FSOC)analog for magnetospheric activity

It has been suggested that the dynamics of the magnetotail may exhibit forced and/or self-organized critical behaviour. Recent analysis of experimental data seem to be in concert with this idea. These suggestions and indications have re-motivated interest in sandpile (avalanche) models. Some examples of specific interest for geomagnetic activity have the property that internal avalanches exhibit inverse power law statistics whereas systemwide avalanches have a well-defined mean. Here we apply the concept of a renormalization group to such a model. We demonstrate that invariant analysis based on the renormalization-group theory can explain the power law distribution of energy release by internal avalanches in then large-scale regime of these systems

Complexity Induced Anisotropic Bimodal Intermittent Turbulence in Space Plasmas

The "physics of complexity" in space plasmas is the central theme of this exposition. It is demonstrated that the sporadic and localized interactions of magnetic coherent structures arising from the plasma resonances can be the source for the coexistence of nonpropagating spatiotemporal fluctuations and propagating modes. Non-Gaussian probability distribution functions of the intermittent fluctuations from direct numerical simulations are obtained and discussed. Power spectra and local intermittency measures using the wavelet analyses are presented to display the spottiness of the small-scale turbulent fluctuations and the non-uniformity of coarse-grained dissipation that can lead to magnetic topological reconfigurations. The technique of the dynamic renormalization group is applied to the study of the scaling properties of such type of multiscale fluctuations. Charged particle interactions with both the propagating and nonpropagating portions of the intermittent turbulence are also described

Analytical determination of power-law index for the Chapman et al. sandpile (FSOC) analog for magnetospheric activity - a renormalization-group analysis

Recent suggestion and experimental indications that the magnetotail dynamics exhibit self-organized critical behavior have re-motivated interest in sandpile (avalanche) models. Some examples of specific interest for geomagnetic activity have the property that internal avalanches exhibit inverse power law statistics whereas systemwide avalanches have a well-defined mean. Here, we apply the concept of renormalization group to such a model. We demonstrate that invariant analysis based on the renormalization-group theory can explain the power law distribution of energy release by internal avalanches in the large-scale regime of these systems

Low-energy particle experiments–electron analyzer (LEPe) onboard the Arase spacecraft

Abstract In this report, we describe the low-energy electron instrument LEPe (low-energy particle experiments–electron analyzer) onboard the Arase (ERG) spacecraft. The instrument measures a three-dimensional distribution function of electrons with energies of $$\sim 19$$ ∼ 19  eV–19 keV. Electrons in this energy range dominate in the inner magnetosphere, and measurement of such electrons is important in terms of understanding the magnetospheric dynamics and wave–particle interaction. The instrument employs a toroidal tophat electrostatic energy analyzer with a passive 6-mm aluminum shield. To minimize background radiation effects, the analyzer has a background channel, which monitors counts produced by background radiation. Background counts are then subtracted from measured counts. Electronic components are radiation tolerant, and 5-mm-thick shielding of the electronics housing ensures that the total dose is less than 100 kRad for the one-year nominal mission lifetime. The first in-space measurement test was done on February 12, 2017, showing that the instrument functions well. On February 27, the first all-instrument run test was done, and the LEPe instrument measured an energy dispersion event probably related to a substorm injection occurring immediately before the instrument turn-on. These initial results indicate that the instrument works fine in space, and the measurement performance is good for science purposes