scholarly journals Gyroresonant wave-particle interactions with chorus waves during extreme depletions of plasma density in the Van Allen radiation belts

2021 ◽  
Vol 7 (5) ◽  
pp. eabc0380
Author(s):  
Hayley J. Allison ◽  
Yuri Y. Shprits ◽  
Irina S. Zhelavskaya ◽  
Dedong Wang ◽  
Artem G. Smirnov
Keyword(s):  
Plasma Density ◽  
Particle Interactions ◽  
Number Density ◽  
Chorus Waves ◽  
Energetic Radiation ◽  
Radiation Belt Electrons ◽  
Diffusive Acceleration ◽  
Extreme Cold ◽  
Plasma Depletion

The Van Allen Probes mission provides unique measurements of the most energetic radiation belt electrons at ultrarelativistic energies. Simultaneous observations of plasma waves allow for the routine inference of total plasma number density, a parameter that is very difficult to measure directly. On the basis of long-term observations in 2015, we show that the underlying plasma density has a controlling effect over acceleration to ultrarelativistic energies, which occurs only when the plasma number density drops down to very low values (~10 cm–3). Such low density creates preferential conditions for local diffusive acceleration of electrons from hundreds of kilo–electron volts up to >7 MeV. While previous models could not reproduce the local acceleration of electrons to such high energies, here we complement the observations with a numerical model to show that the conditions of extreme cold plasma depletion result in acceleration up to >7 MeV.

Radiation belt electron acceleration during periods of low plasma density

2021 ◽  
Author(s):  
Hayley Allison ◽  
Yuri Shprits ◽  
Irina Zhelavskaya ◽  
Dedong Wang ◽  
Artem Smirnov
Keyword(s):  
Plasma Density ◽  
Cold Plasma ◽  
Radiation Belt ◽  
Electron Acceleration ◽  
Number Density ◽  
Chorus Waves ◽  
Radiation Belt Electrons ◽  
Plasma Depletion

<p>Electrons in the Van Allen radiation belts can have energies in excess of 7 MeV. We present a unique way of analyzing phase space density data which demonstrates that local acceleration is capable of heating electrons up to 7 MeV. The Van Allen Probes mission not only provided unique measurements of ultra-relativistic radiation belt electrons, but also simultaneous observations of plasma waves that allowed for the routine inference of total plasma number density. Based on long-term observations, we show that the underlying plasma density has a controlling effect over local acceleration to ultra-relativistic energies, which occurs only when the plasma number density drops down to very low values (~10 cm<sup>-3</sup>). The VERB-2D model is used to simulate ultra-relativistic electron acceleration during an event which exhibits an extreme cold plasma depletion. The results show that a reduced electron plasma density allows chorus waves to efficiently resonate with electrons up to ultra-relativistic energies, producing enhancements from 100s of keV up to >7 MeV via local diffusive acceleration. We analyse statistically the observed chorus wave power during ultra-relativistic enhancement events, considering the contribution from both upper and lower band chorus waves. The PINE density model allows for the investigation of global magnetospheric density changes. We analyze the how the global cold plasma density changes during ultra-relativistic enhancement events and compare to in-situ point measurements of the plasma density.</p>

scholarly journals A Comparison of Radial Diffusion Coefficients in 1-D and 3-D Long-Term Radiation Belt Simulations

2020 ◽  
Author(s):  
Alexander Drozdov ◽  
Hayley Allison ◽  
Yuri Shprits ◽  
Nikita Aseev
Keyword(s):  
Radiation Belt ◽  
Low Frequency ◽  
Radial Diffusion ◽  
Ulf Waves ◽  
Electron Radiation ◽  
Particle Interactions ◽  
Physical Mechanisms ◽  
Modeling And Forecasting ◽  
Radiation Belt Electrons

<p>Radial diffusion is one of the dominant physical mechanisms that drives acceleration andloss of the radiation belt electrons due to wave-particle interactions with ultra-low frequency (ULF) waves, which makes it very important for radiation belt modeling and forecasting.  We investigate the sensitivity of several parameterizations of the radial diffusion including Brautigam and Albert (2000), Ozeke et al. (2014), Ali et al. (2016), and Liu et al. (2016) on long-term radiation belt modeling using the Versatile Electron Radiation Belt (VERB) code.  Following previous studies, we first perform 1-D radial diffusion simulations.  To take into account effects of local acceleration and loss, we perform additional 3-D simulations, including pitch-angle, energy and mixed diffusion.</p>

scholarly journals Effect of plasma density on diffusion rates due to wave particle interactions with chorus and plasmaspheric hiss: extreme event analysis

2014 ◽  
Vol 32 (8) ◽  
pp. 1059-1071 ◽  
Author(s):  
A. Sicard-Piet ◽  
D. Boscher ◽  
R. B. Horne ◽  
N. P. Meredith ◽  
V. Maget
Keyword(s):  
Electron Density ◽  
Plasma Density ◽  
Radiation Belts ◽  
Cumulative Distribution ◽  
Cumulative Probability ◽  
Particle Interactions ◽  
Energy Diffusion ◽  
Chorus Waves ◽  
Diffusion Rates ◽  
Wave Particle Interactions

Abstract. Wave particle interactions play an important role in controlling the dynamics of the radiation belts. The purpose of this study is to estimate how variations in the plasma density can affect diffusion rates resulting from interactions between chorus waves and plasmaspheric hiss with energetic particles and the resulting evolution of the energetic electron population. We perform a statistical analysis of the electron density derived from the plasma wave experiment on the CRRES satellite for two magnetic local time sectors corresponding to near midnight and near noon. We present the cumulative probability distribution of the electron plasma density for three levels of magnetic activity as measured by Kp. The largest densities are seen near L* = 2.5 while the smallest occur near L* = 6. The broadest distribution, corresponding to the greatest variability, occurs near L* = 4. We calculate diffusion coefficients for plasmaspheric hiss and whistler mode chorus for extreme values of the electron density and estimate the effects on the radiation belts using the Salammbô model. At L* = 4 and L* = 6, in the low density case, using the density from the 5th percentile of the cumulative distribution function, electron energy diffusion by chorus waves is strongest at 2 MeV and increases the flux by up to 3 orders of magnitude over a period of 24 h. In contrast, in the high density case, using the density from the 95th percentile, there is little acceleration at energies above 800 keV at L* = 6, and virtually no acceleration at L* = 4. In this case the strongest energy diffusion occurs at lower energies around 400 keV where the flux at L* = 6 increases 3 orders of magnitude.

Interface Energy-driven Indium Whisker Growth on Ceramic Substrates 

2021 ◽  
Author(s):  
Shuai Li ◽  
Yushuang Liu ◽  
Peigen Zhang ◽  
Yan Zhang ◽  
Chengjie Lu ◽  
...  
Keyword(s):  
Whisker Growth ◽  
Interface Energy ◽  
Mitigation Strategy ◽  
Max Phase ◽  
Number Density ◽  
Ceramic Substrates ◽  
Liquid Indium ◽  
Reliability Of Electronics

Abstract The mechanism behind spontaneous growth of metal whiskers is essential to develop lead-free whisker mitigation strategy for the sake of long-term reliability of electronics, and has been sought for several decades. However, a consensus about it still lacks, and a host of factors influencing the phenomenon have been investigated, but the role of interface energy has not been paid adequate attention. In this study, the whisker growth propensities of ball-milled Ti2InC/In and non-MAX phase TiC/In and SiC/In are comparatively studied in the terms of the wettability, thermal behavior and crystal structures. The wetting angles of indium with Ti2InC, TiC, and SiC (144.4°, 155.7°, and 142.2°, respectively) are large and quite close, indicating the poor wettability between liquid indium and the three ceramics. The thermal behaviors of all the three systems have obvious changes after ball milling. The number density of indium whiskers on ball-milled Ti2InC are significantly greater than those on the TiC and SiC substrates, which is explained based on interface energy and the crystal structure difference of the ceramic substrates.

Simulations of the Relativistic Radiation Belt Electrons Using the VERB-3D Code

2021 ◽  
Author(s):  
Dedong Wang ◽  
Yuri Shprits ◽  
Alexander Drozdov ◽  
Nikita Aseev ◽  
Irina Zhelavskaya ◽  
...  
Keyword(s):  
Space Weather ◽  
Radiation Belt ◽  
Model Performance ◽  
Dynamic Evolution ◽  
Relativistic Electrons ◽  
Outer Radiation Belt ◽  
Chorus Waves ◽  
Van Allen Probes ◽  
Radiation Belt Electrons ◽  
Simulation Results

<p>Using the three-dimensional Versatile Electron Radiation Belt (VERB-3D) code, we perform simulations to investigate the dynamic evolution of relativistic electrons in the Earth’s outer radiation belt. In our simulations, we use data from the Geostationary Operational Environmental Satellites (GOES) to set up the outer boundary condition, which is the only data input for simulations. The magnetopause shadowing effect is included by using last closed drift shell (LCDS), and it is shown to significantly contribute to the dropouts of relativistic electrons at high $L^*$. We validate our simulation results against measurements from Van Allen Probes. In long-term simulations, we test how the latitudinal dependence of chorus waves can affect the dynamics of the radiation belt electrons. Results show that the variability of chorus waves at high latitudes is critical for modeling of megaelectron volt (MeV) electrons. We show that, depending on the latitudinal distribution of chorus waves under different geomagnetic conditions, they cannot only produce a net acceleration but also a net loss of MeV electrons. Decrease in high‐latitude chorus waves can tip the balance between acceleration and loss toward acceleration, or alternatively, the increase in high‐latitude waves can result in a net loss of MeV electrons. Variations in high‐latitude chorus may account for some of the variability of MeV electrons. </p><p>Our simulation results for the NSF GEM Challenge Events show that the position of the plasmapause plays a significant role in the dynamic evolution of relativistic electrons. We also perform simulations for the COSPAR International Space Weather Action Team (ISWAT) Challenge for the year 2017. The COSPAR ISWAT is a global hub for collaborations addressing challenges across the field of space weather. One of the objectives of the G3-04 team “Internal Charging Effects and the Relevant Space Environment” is model performance assessment and improvement. One of the expected outputs is a more systematic assessment of model performance under different conditions. The G3-04 team proposed performing benchmarking challenge runs. We ‘fly’ a virtual satellite through our simulation results and compare the simulated differential electron fluxes at 0.9 MeV and 57.27 degrees local pitch-angle with the fluxes measured by the Van Allen Probes. In general, our simulation results show good agreement with observations. We calculated several different matrices to validate our simulation results against satellite observations.</p>

scholarly journals The Distant DRAGNs Survey

1996 ◽  
Vol 175 ◽  
pp. 513-514
Author(s):  
J. D. B. Law-Green
Keyword(s):  
Flux Density ◽  
Ambient Medium ◽  
High Redshift ◽  
Galactic Nuclei ◽  
Cosmological Evolution ◽  
Radio Sources ◽  
Number Density ◽  
Extragalactic Radio Sources ◽  
Matched Samples

DRAGNs (Double Radio sources Associated with Galactic Nuclei, Leahy 1991) are the class of powerful extragalactic radio sources thought to be produced by the interaction of a jet with the ambient medium. They exhibit strong cosmological evolution in comoving number density; at z ≃ 2 the “classical double” FR II DRAGNs were ≃ 1000 times as common as they are now (Dunlop & Peacock 1990).To understand this, systematic studies of complete DRAGN samples at low and high z and differing levels of flux density are required, in order to resolve the P – z ambiguity. The Distant DRAGNs Survey is a long-term project to image with the VLA and MERLIN, matched samples of DRAGNs at high redshift.

scholarly journals Hatching delays in great tits and blue tits in response to an extreme cold spell: a long-term study

2018 ◽  
Vol 62 (8) ◽  
pp. 1437-1445 ◽  
Author(s):  
Michał Glądalski ◽  
Mirosława Bańbura ◽  
Adam Kaliński ◽  
Marcin Markowski ◽  
Joanna Skwarska ◽  
...  
Keyword(s):  
Cold Spell ◽  
Term Study ◽  
Long Term Study ◽  
Extreme Cold ◽  
Blue Tits
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