The Magnetospheric “Zebra Stripes”: A Tracer of Near-Earth Space Dynamics

2021 ◽  
Author(s):  
Solène Lejosne ◽  
Forrest S. Mozer
Keyword(s):  
Electric Fields ◽  
Radiation Belt ◽  
Periodic Structures ◽  
High Energy ◽  
High Energy Resolution ◽  
Stripe Pattern ◽  
Near Earth Space ◽  
The Earth ◽  
Space Dynamics ◽  
First Time

<p>High-energy resolution measurements of energetic (tens to hundreds of keV) electron fluxes in the Earth’s inner radiation belt and slot region (below L~ 3) revealed the presence of drift-periodic structures named the “zebra stripes”.</p><p>We show that analyzing the characteristics of the zebra stripes provides a new tool to shed light on important, yet mostly uncharted drivers of the Earth’s inner magnetosphere, namely, (a) radial displacements of geomagnetically trapped particles in the inner belt and slot region, and (b) electric field variations in the subauroral region.</p><p>With the large database of high-quality observations provided by the NASA Van Allen Probes mission, it is for the first time possible to perform long-term statistical analysis of the zebra stripe pattern.</p><p>Because Earth-like zebra stripes were also recently discovered at Saturn, the analysis of the zebra stripes present at Earth could constitute a benchmark to determine the electric fields and associated radiation belt dynamics at other magnetized planets.</p>

scholarly journals RADIATION HAZARD ON EARTH AND IN NEAR-EARTH SPACE DURING MAGNETIC FIELD INVERSION

2019 ◽  
Vol 47 (1) ◽  
pp. 129-131
Author(s):  
O.O. Tsareva ◽  
V.Yu. Popov ◽  
H.V. Malova ◽  
E.P. Popova ◽  
M.V. Podzolko ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Energy ◽  
Field Configuration ◽  
Radiation Hazard ◽  
Dynamo Model ◽  
Earth Space ◽  
Near Earth Space ◽  
The Earth ◽  
The Magnetic Field ◽  
Field Inversion

Recent observations, such as the magnetic field strength decrease, a magnetic poles shifts and the South Atlantic anomaly increase, may indicate the beginning of the Earth’s magnetic field inversion. According to the geomagnetic dynamo model, the dipole component of the magnetic field is zeroed at the inversion time, and the quadrupole one becomes dominant. To assess the occurrence of radiation hazards on the Earth’s surface and in near-Earth space at the time of magnetic field inversion, a numerical model was developed that made it possible to compare the GCR and SCR fluxes (at minima and maxima of solar activity) penetrating the Earth (taking into account the atmosphere) and the ISS in periods of the dipole and quadrupole fields dominance. It was found that during the period of inversion the flow of GCR (high-energy particles) can increase no more than three times over the entire surface of the Earth and the radiation dose will not exceed permissible one for man. Also, a change of the magnetic field configuration will redistribute areas of increased radiation on the Earth’s surface (today these are the poles of the Earth), which can adversely affect people’s health in these areas.

High-pressure X-ray science on the ultimate storage ring

2014 ◽  
Vol 21 (5) ◽  
pp. 1077-1083 ◽  
Author(s):  
Malcolm I. McMahon
Keyword(s):  
High Pressure ◽  
High Energy ◽  
Storage Rings ◽  
Nuclear Scattering ◽  
New Techniques ◽  
X Ray ◽  
The Earth ◽  
New Generation ◽  
First Time ◽  
Insight Into

The advent of the ESRF, APS and SPring-8 third-generation synchrotron sources in the mid-1990s heralded a golden age of high-pressure X-ray science. The high-energy monochromatic micro-focused X-ray beams from these storage rings, combined with the new high-pressure diffraction and spectroscopy techniques developed in the late 1980s, meant that researchers were immediately able to make detailed structural studies at pressures comparable with those at the centre of the Earth, studies that were simply not possible only five years previously. And new techniques, such as X-ray inelastic scattering and X-ray nuclear scattering, became possible at high pressure for the first time, providing wholly-new insight into the behaviour of materials at high densities. The arrival of new diffraction-limited storage rings, with their much greater brightness, and ability to achieve focal-spot diameters for high-energy X-ray beams of below 1 µm, offers the possibility of a new generation of high-pressure science, both extending the scope of what is already possible, and also opening ways to wholly-new areas of investigation.

scholarly journals Laboratory and near-earth space plasma as a key to the plasma universe

1988 ◽  
Vol 6 (3) ◽  
pp. 437-452 ◽  
Author(s):  
Carl-Gunne Fälthammar
Keyword(s):  
Electric Fields ◽  
Chemical Separation ◽  
Space Plasma ◽  
High Energy ◽  
Stored Energy ◽  
Near Earth Space ◽  
Neutral Gas ◽  
Rapid Release ◽  
Plasma State

Experiments in the laboratory and in situ measurements in space represent an essential, but often overlooked, key to reliable understanding of our plasma universe. This will be illustrated by discussing several fundamental aspects of matter in the plasma state. They include (1) conduction of electric current, (2) magnetic-field aligned electric fields, (3) acceleration of charged particles to high energy, (4) coupling between magnetic fields and the motion of matter, (5) rapid release of magnetically stored energy, (6) chemical separation, and (7) critical-velocity interaction between plasma and neutral gas.

Thermospheric Neutral Winds: A Driver of the Earth’s Inner Radiation Belt to Be Reckoned With

2021 ◽  
Author(s):  
Solène Lejosne ◽  
Naomi Maruyama ◽  
Richard S. Selesnick ◽  
Mariangel Fedrizzi
Keyword(s):  
Electric Fields ◽  
Radiation Belt ◽  
Coupled Model ◽  
Plasma Dynamics ◽  
Time Asymmetry ◽  
Neutral Winds ◽  
Tidal Motion ◽  
The Earth ◽  
Field Lines ◽  
The Impact

<p>Neutral winds have long been viewed as a driver of Jupiter’s radiation belts. On the other hand, the impact of thermospheric neutral winds in driving plasma dynamics in the Earth’s inner magnetosphere is yet to be quantified. We now have the appropriate combination of data and physics-based model to address this fundamental science question.</p><p>In this work, we revisit the local time asymmetry of the equatorial electron intensity observed in the innermost radiation belt (L=1.30). We combine in-situ field and particle observations, together with a physics-based coupled model, RCM-CTIPe, to determine whether the dynamo electric fields produced by tidal motion of upper atmospheric winds flowing across the Earth’s magnetic field lines are the main drivers of the drift-shell distortion observed in the Earth’s inner radiation belt.</p><p>Our results provide a first quantification of the contribution of the neutral wind in transporting the trapped energetic particles of the Earth’s inner radiation belt.</p>

scholarly journals High-resolution X-ray absorption spectroscopy as a probe of crystal-field and covalency effects in actinide compounds

2016 ◽  
Vol 113 (29) ◽  
pp. 8093-8097 ◽  
Author(s):  
Sergei M. Butorin ◽  
Kristina O. Kvashnina ◽  
Johan R. Vegelius ◽  
Daniel Meyer ◽  
David K. Shuh
Keyword(s):  
Absorption Spectroscopy ◽  
Ground State ◽  
High Energy ◽  
High Energy Resolution ◽  
Crystalline Electric Field ◽  
X Ray ◽  
Anderson Impurity Model ◽  
First Time ◽  
X Ray Absorption

Applying the high-energy resolution fluorescence-detection (HERFD) mode of X-ray absorption spectroscopy (XAS), we were able to probe, for the first time to our knowledge, the crystalline electric field (CEF) splittings of the5fshell directly in the HERFD-XAS spectra of actinides. Using ThO2as an example, data measured at the Th 3dedge were interpreted within the framework of the Anderson impurity model. Because the charge-transfer satellites were also resolved in the HERFD-XAS spectra, the analysis of these satellites revealed that ThO2is not an ionic compound as previously believed. The Th6doccupancy in the ground state was estimated to be twice that of the Th5fstates. We demonstrate that HERFD-XAS allows for characterization of the CEF interaction and degree of covalency in the ground state of actinide compounds as it is extensively done for 3dtransition metal systems.

High energy resolution spectrometer for the dedicated STEM

1984 ◽  
Vol 42 ◽  
pp. 558-559 ◽  
Author(s):  
P.E. Batson
Keyword(s):  
Collection Efficiency ◽  
Core Loss ◽  
Beam Current ◽  
High Energy ◽  
High Energy Resolution ◽  
Acquisition Time ◽  
Good Definition ◽  
Loss Analysis ◽  
Definition Of ◽  
Acceleration Voltage

Use of the STEM to obtain precise electronic information has been hampered by the lack of energy loss analysis capable of a resolution and accuracy comparable to the 0.3eV energy width of the Field Emission Source. Recent work by Park, et. al. and earlier by Crewe, et. al. have promised magnetic sector devices that are capable of about 0.75eV resolution at collection angles (about 15mR) which are great enough to allow efficient use of the STEM probe current. These devices are also capable of 0.3eV resolution at smaller collection angles (4-5mR). The problem that arises, however, lies in the fact that, even with the collection efficiency approaching 1.0, several minutes of collection time are necessary for a good definition of a typical core loss or electronic transition. This is a result of the relatively small total beam current (1-10nA) that is available in the dedicated STEM. During this acquisition time, the STEM acceleration voltage may fluctuate by as much as 0.5-1.0V.

Observation of High-Energy Particles in the Inner Radiation Belt by the HEP Instrument of the Arase Satellite

2020 ◽  
Vol 18 (6) ◽  
pp. 398-403
Author(s):  
Honoka TODA ◽  
Wataru MIYAKE ◽  
Takefumi MITANI ◽  
Takeshi TAKASHIMA ◽  
Yoshizumi MIYOSHI ◽  
...  
Keyword(s):  
Radiation Belt ◽  
High Energy ◽  
High Energy Particles

scholarly journals Mechanochemical Synthesis and Nitrogenation of the Nd1.1Fe10CoTi Alloy for Permanent Magnet

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3854
Author(s):  
Hugo Martínez Sánchez ◽  
George Hadjipanayis ◽  
Germán Antonio Pérez Alcázar ◽  
Ligia Edith Zamora Alfonso ◽  
Juan Sebastián Trujillo Hernández
Keyword(s):  
Mechanochemical Synthesis ◽  
Applied Field ◽  
Volume Fraction ◽  
Synthesis Method ◽  
High Energy ◽  
Direction Parallel ◽  
Best Value ◽  
Heat Treated ◽  
Bcc Phase ◽  
First Time

In this work, the mechanochemical synthesis method was used for the first time to produce powders of the nanocrystalline Nd1.1Fe10CoTi compound from Nd2O3, Fe2O3, Co and TiO2. High-energy-milled powders were heat treated at 1000 °C for 10 min to obtain the ThMn12-type structure. Volume fraction of the 1:12 phase was found to be as high as 95.7% with 4.3% of a bcc phase also present. The nitrogenation process of the sample was carried out at 350 °C during 3, 6, 9 and 12 h using a static pressure of 80 kPa of N2. The magnetic properties Mr, µ0Hc, and (BH)max were enhanced after nitrogenation, despite finding some residual nitrogen-free 1:12 phase. The magnetic values of a nitrogenated sample after 3 h were Mr = 75 Am2 kg–1, µ0Hc = 0.500 T and (BH)max = 58 kJ·m–3. Samples were aligned under an applied field of 2 T after washing and were measured in a direction parallel to the applied field. The best value of (BH)max~114 kJ·m–3 was obtained for 3 h and the highest µ0Hc = 0.518 T for 6 h nitrogenation. SEM characterization revealed that the particles have a mean particle size around 360 nm and a rounded shape.

scholarly journals Insights on forming N,O-coordinated Cu single-atom catalysts for electrochemical reduction CO2 to methane

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yanming Cai ◽  
Jiaju Fu ◽  
Yang Zhou ◽  
Yu-Chung Chang ◽  
Qianhao Min ◽  
...  
Keyword(s):  
Energy Barrier ◽  
Active Sites ◽  
Theoretical Calculations ◽  
High Energy ◽  
Single Atom ◽  
Faradaic Efficiency ◽  
High Energy Barrier ◽  
Catalytic Sites ◽  
Electron Reduction ◽  
First Time

AbstractSingle-atom catalysts (SACs) are promising candidates to catalyze electrochemical CO2 reduction (ECR) due to maximized atomic utilization. However, products are usually limited to CO instead of hydrocarbons or oxygenates due to unfavorable high energy barrier for further electron transfer on synthesized single atom catalytic sites. Here we report a novel partial-carbonization strategy to modify the electronic structures of center atoms on SACs for lowering the overall endothermic energy of key intermediates. A carbon-dots-based SAC margined with unique CuN2O2 sites was synthesized for the first time. The introduction of oxygen ligands brings remarkably high Faradaic efficiency (78%) and selectivity (99% of ECR products) for electrochemical converting CO2 to CH4 with current density of 40 mA·cm-2 in aqueous electrolytes, surpassing most reported SACs which stop at two-electron reduction. Theoretical calculations further revealed that the high selectivity and activity on CuN2O2 active sites are due to the proper elevated CH4 and H2 energy barrier and fine-tuned electronic structure of Cu active sites.

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