scholarly journals Earth’s magnetotail as the reservoir of accelerated single- and multicharged oxygen ions replenishing radiation belts

2020 ◽  
Author(s):  
Elena Parkhomenko ◽  
Vladimir Kalegaev ◽  
Helmi Malova ◽  
Mikhail Panasyuk ◽  
Victor Popov ◽  
...  
Keyword(s):  
Numerical Model ◽  
Time Scale ◽  
Large Scale ◽  
Radiation Belt ◽  
Ring Current ◽  
Outer Region ◽  
Radiation Belts ◽  
Proton Radiation ◽  
Oxygen Ions ◽  
Oxygen Ion

<p>In this work we are studying multicharged oxygen ion acceleration during substorms in the Earth's magnetotail as the source of ring current replenishment by energetic ion population. We used measurements obtained by the CRRES spacecraft for the comparison of experimental spectra of oxygen charge state in the outer region of the ring current and proton radiation belt with model results. We present a numerical model that allows to evaluate acceleration of oxygen ions O+-O+8 in the course of two possible perturbation processes: A) passage of multiple dipolarization fronts in the magnetotail; B) passage of fronts followed by electromagnetic turbulence. It is shown that acceleration processes depend on particle charges and time scale of electric field variations. Oxygen ions O+8 with average initial energies 12 keV are accelerated efficiently during multiple dipolarization processes of type (A) and their energies increased up to 7.4 MeV, whereas ions O+1 with the same energies were energized up to 1.9 МeV. It is shown that oxygen ions O+-O+2 are able to penetrate into the ring/radiation belts region with L between L=4.5 and L=7.5 in the process of plasma transfer on dipolarization fronts. For oxygen O+-O+8 the additional acceleration mechanism is required, such as large-scale electromagnetic turbulence, when the ions can get energies comparable with experimentally observed ones in the indicated range of L shell values. It is shown that the taking into account electromagnetic fluctuations, accompanying magnetic dipolarization, may explain the appearance of oxygen ion flows with energies greater than 3MeV in the near- Earth’s space.</p>

scholarly journals MODEL OF THE INTERACTION OF OXYGEN IONS O+-O+2 WITH DIPOLAZATION FRONTS DURING ELECTROMAGNETIC TURBULENCE IN THE EARTH’S MAGNETOTAIL

2019 ◽  
Vol 47 (1) ◽  
pp. 94-96
Author(s):  
E.I. Parkhomenko ◽  
V.Yu. Popov ◽  
H.V. Malova ◽  
L.M. Zelenyi
Keyword(s):  
Particle Acceleration ◽  
Numerical Model ◽  
Time Scale ◽  
Energy Spectra ◽  
Field Variation ◽  
Plasma Particle ◽  
Oxygen Ions ◽  
A Current ◽  
Different Time Scales ◽  
Accelerated Particles

The paper is devoted to studying processes of plasma particle acceleration in the process of magnetic dipolazations in a current sheet of Earth’s magnetotail. A numerical model is constructed that allows evaluation of oxygen ions O+ – O+2 acceleration in two possible scenarios: (A) Passage of multiple dipolazation fronts; (B) Passage of fronts followed by largescale electromagnetic turbulence. The energy spectra of two types of accelerated particles are obtained: oxygen O+ and O+2. It is shown that, at different time scales, predominant variety acceleration of particle populations occurs in scenarios (A)–(B). Thus the closer the time scale of the field variation to the ions gyroperiod, the more effective is the transfer of energy from fields to particles. Oxygen ions O+2 are accelerated efficiently in multiple dipolazation process (B) and increase energy up to 3 MeV , whereas ions O+ - up to 1.7 МeV. It is shown that accounting for electromagnetic fluctuations, accompanying magnetic dipolazation, may explain the appearance of streams of oxygen ions with energies greater than 3MeV in Earth’s magnetotail.

scholarly journals The atmospheric implications of radiation belt remediation

2006 ◽  
Vol 24 (7) ◽  
pp. 2025-2041 ◽  
Author(s):  
C. J. Rodger ◽  
M. A. Clilverd ◽  
Th. Ulich ◽  
P. T. Verronen ◽  
E. Turunen ◽  
...  
Keyword(s):  
Large Scale ◽  
Radiation Belt ◽  
Geomagnetic Storms ◽  
Operation Time ◽  
Solar Proton ◽  
Radiation Belts ◽  
Navigation Systems ◽  
Neutral Atmosphere ◽  
Radio Communication ◽  
Nuclear Explosions

Abstract. High altitude nuclear explosions (HANEs) and geomagnetic storms can produce large scale injections of relativistic particles into the inner radiation belts. It is recognised that these large increases in >1 MeV trapped electron fluxes can shorten the operational lifetime of low Earth orbiting satellites, threatening a large, valuable population. Therefore, studies are being undertaken to bring about practical human control of the radiation belts, termed "Radiation Belt Remediation" (RBR). Here we consider the upper atmospheric consequences of an RBR system operating over either 1 or 10 days. The RBR-forced neutral chemistry changes, leading to NOx enhancements and Ox depletions, are significant during the timescale of the precipitation but are generally not long-lasting. The magnitudes, time-scales, and altitudes of these changes are no more significant than those observed during large solar proton events. In contrast, RBR-operation will lead to unusually intense HF blackouts for about the first half of the operation time, producing large scale disruptions to radio communication and navigation systems. While the neutral atmosphere changes are not particularly important, HF disruptions could be an important area for policy makers to consider, particularly for the remediation of natural injections.

Large-scale Motion of Solar Filaments

2000 ◽  
Vol 179 ◽  
pp. 205-208
Author(s):  
Pavel Ambrož ◽  
Alfred Schroll
Keyword(s):  
Magnetic Flux ◽  
Proper Motion ◽  
Time Scale ◽  
Large Scale ◽  
Accuracy Of Measurements ◽  
Solar Filaments ◽  
General Movement ◽  
Scale Motion ◽  
Velocity Scatter

AbstractPrecise measurements of heliographic position of solar filaments were used for determination of the proper motion of solar filaments on the time-scale of days. The filaments have a tendency to make a shaking or waving of the external structure and to make a general movement of whole filament body, coinciding with the transport of the magnetic flux in the photosphere. The velocity scatter of individual measured points is about one order higher than the accuracy of measurements.

scholarly journals Graphene-Based Artificial Synapses with Tunable Plasticity

2021 ◽  
Vol 17 (4) ◽  
pp. 1-21
Author(s):  
He Wang ◽  
Nicoleta Cucu Laurenciu ◽  
Yande Jiang ◽  
Sorin Cotofana
Keyword(s):  
Synaptic Plasticity ◽  
Weight Change ◽  
Time Scale ◽  
Large Scale ◽  
Synaptic Weight ◽  
Low Voltage ◽  
Logic Gates ◽  
Full Potential ◽  
Back Gate ◽  
Input Spike

Design and implementation of artificial neuromorphic systems able to provide brain akin computation and/or bio-compatible interfacing ability are crucial for understanding the human brain’s complex functionality and unleashing brain-inspired computation’s full potential. To this end, the realization of energy-efficient, low-area, and bio-compatible artificial synapses, which sustain the signal transmission between neurons, is of particular interest for any large-scale neuromorphic system. Graphene is a prime candidate material with excellent electronic properties, atomic dimensions, and low-energy envelope perspectives, which was already proven effective for logic gates implementations. Furthermore, distinct from any other materials used in current artificial synapse implementations, graphene is biocompatible, which offers perspectives for neural interfaces. In view of this, we investigate the feasibility of graphene-based synapses to emulate various synaptic plasticity behaviors and look into their potential area and energy consumption for large-scale implementations. In this article, we propose a generic graphene-based synapse structure, which can emulate the fundamental synaptic functionalities, i.e., Spike-Timing-Dependent Plasticity (STDP) and Long-Term Plasticity . Additionally, the graphene synapse is programable by means of back-gate bias voltage and can exhibit both excitatory or inhibitory behavior. We investigate its capability to obtain different potentiation/depression time scale for STDP with identical synaptic weight change amplitude when the input spike duration varies. Our simulation results, for various synaptic plasticities, indicate that a maximum 30% synaptic weight change and potentiation/depression time scale range from [-1.5 ms, 1.1 ms to [-32.2 ms, 24.1 ms] are achievable. We further explore the effect of our proposal at the Spiking Neural Network (SNN) level by performing NEST-based simulations of a small SNN implemented with 5 leaky-integrate-and-fire neurons connected via graphene-based synapses. Our experiments indicate that the number of SNN firing events exhibits a strong connection with the synaptic plasticity type, and monotonously varies with respect to the input spike frequency. Moreover, for graphene-based Hebbian STDP and spike duration of 20ms we obtain an SNN behavior relatively similar with the one provided by the same SNN with biological STDP. The proposed graphene-based synapse requires a small area (max. 30 nm 2 ), operates at low voltage (200 mV), and can emulate various plasticity types, which makes it an outstanding candidate for implementing large-scale brain-inspired computation systems.

Interaction of ring current and radiation belt protons with ducted plasmaspheric hiss: 1. Diffusion coefficients and timescales

1994 ◽  
Vol 99 (A3) ◽  
pp. 4069 ◽  
Author(s):  
J. U. Kozyra ◽  
C. E. Rasmussen ◽  
R. H. Miller ◽  
L. R. Lyons
Keyword(s):  
Diffusion Coefficients ◽  
Radiation Belt ◽  
Ring Current

Earth's magnetotail as the reservoir of accelerated single‐ and multicharged oxygen ions replenishing radiation belts

2021 ◽  
Author(s):  
M. I. Panasyuk ◽  
E. I. Zhukova ◽  
V. V. Kalegaev ◽  
H. V. Malova ◽  
V.Yu. Popov ◽  
...  
Keyword(s):  
Radiation Belts ◽  
Oxygen Ions

On the effect of ULF waves on the outer radiation belt during geomagnetic storms

2021 ◽  
Author(s):  
Christopher Lara ◽  
Pablo S. Moya ◽  
Victor Pinto ◽  
Javier Silva ◽  
Beatriz Zenteno
Keyword(s):  
Relativistic Electron ◽  
Radiation Belt ◽  
Geomagnetic Storms ◽  
Cumulative Effect ◽  
Radiation Belts ◽  
Ulf Waves ◽  
Relativistic Electrons ◽  
Relative Role ◽  
Outer Radiation Belt ◽  
Ulf Wave

<p>The inner magnetosphere is a very important region to study, as with satellite-based communications increasing day after day, possible disruptions are especially relevant due to the possible consequences in our daily life. It is becoming very important to know how the radiation belts behave, especially during strong geomagnetic activity. The radiation belts response to geomagnetic storms and solar wind conditions is still not fully understood, as relativistic electron fluxes in the outer radiation belt can be depleted, enhanced or not affected following intense activity. Different studies show how these results vary in the face of different events. As one of the main mechanisms affecting the dynamics of the radiation belt are wave-particle interactions between relativistic electrons and ULF waves. In this work we perform a statistical study of the relationship between ULF wave power and relativistic electron fluxes in the outer radiation belt during several geomagnetic storms, by using magnetic field and particle fluxes data measured by the Van Allen Probes between 2012 and 2017. We evaluate the correlation between the changes in flux and the cumulative effect of ULF wave activity during the main and recovery phases of the storms for different position in the outer radiation belt and energy channels. Our results show that there is a good correlation between the presence of ULF waves and the changes in flux during the recovery phase of the storm and that correlations vary as a function of energy. Also, we can see in detail how the ULF power change for the electron flux at different L-shell We expect these results to be relevant for the understanding of the relative role of ULF waves in the enhancements and depletions of energetic electrons in the radiation belts for condition described.</p>

scholarly journals Use of recent geoid models to estimate mean dynamic topography and geostrophic currents in South Atlantic and Brazil Malvinas confluence

2012 ◽  
Vol 60 (1) ◽  
pp. 41-48
Author(s):  
Alexandre Bernardino Lopes ◽  
Joseph Harari
Keyword(s):  
Numerical Model ◽  
Large Scale ◽  
Singular Spectrum Analysis ◽  
Satellite System ◽  
South Atlantic ◽  
Dynamic Topography ◽  
Geostrophic Currents ◽  
Mean Dynamic Topography ◽  
Level Model

The use of geoid models to estimate the Mean Dynamic Topography was stimulated with the launching of the GRACE satellite system, since its models present unprecedented precision and space-time resolution. In the present study, besides the DNSC08 mean sea level model, the following geoid models were used with the objective of computing the MDTs: EGM96, EIGEN-5C and EGM2008. In the method adopted, geostrophic currents for the South Atlantic were computed based on the MDTs. In this study it was found that the degree and order of the geoid models affect the determination of TDM and currents directly. The presence of noise in the MDT requires the use of efficient filtering techniques, such as the filter based on Singular Spectrum Analysis, which presents significant advantages in relation to conventional filters. Geostrophic currents resulting from geoid models were compared with the HYCOM hydrodynamic numerical model. In conclusion, results show that MDTs and respective geostrophic currents calculated with EIGEN-5C and EGM2008 models are similar to the results of the numerical model, especially regarding the main large scale features such as boundary currents and the retroflection at the Brazil-Malvinas Confluence.

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