scholarly journals Spatially inhomogeneous acceleration of electrons in solar flares

2018 ◽  
Vol 612 ◽  
pp. A64 ◽  
Author(s):  
Duncan J. Stackhouse ◽  
Eduard P. Kontar
Keyword(s):  
Spectral Index ◽  
Solar Flares ◽  
Imaging Spectroscopy ◽  
Finite Size ◽  
High Energy ◽  
Diffusive Transport ◽  
Acceleration Region ◽  
Spatially Distributed ◽  
Flare Region ◽  
First Time

The imaging spectroscopy capabilities of the Reuven Ramaty high energy solar spectroscopic imager (RHESSI) enable the examination of the accelerated electron distribution throughout a solar flare region. In particular, it has been revealed that the energisation of these particles takes place over a region of finite size, sometimes resolved by RHESSI observations. In this paper, we present, for the first time, a spatially distributed acceleration model and investigate the role of inhomogeneous acceleration on the observed X-ray emission properties. We have modelled transport explicitly examining scatter-free and diffusive transport within the acceleration region and compare with the analytic leaky-box solution. The results show the importance of including this spatial variation when modelling electron acceleration in solar flares. The presence of an inhomogeneous, extended acceleration region produces a spectral index that is, in most cases, different from the simple leaky-box prediction. In particular, it results in a generally softer spectral index than predicted by the leaky-box solution, for both scatter-free and diffusive transport, and thus should be taken into account when modelling stochastic acceleration in solar flares.

scholarly journals The Model of the Impulsive Phase of Stellar Flares

1989 ◽  
Vol 104 (2) ◽  
pp. 297-300
Author(s):  
V.P. Grinin ◽  
V.V. Sobolev
Keyword(s):  
Radiative Transfer ◽  
Solar Flares ◽  
Charged Particles ◽  
Impulsive Phase ◽  
High Energy ◽  
Stellar Flares ◽  
Flare Region ◽  
Optical Continuum

AbstractThe arguments in favour of that the primary heating of the gas at the impulsive phase of stellar flares is caused by charged particles of higher energies than in the solar flares are given. It is shown that the model of the deep heating by high energy protons (E ≃ 10 MeV) or electrons (E ≃ 100 keV) with taken into account of the radiative transfer in flare region explane the main properties of the optical continuum of the flare.

Energetic electrons in solar flares: observational support for acceleration processes linked to magnetic reconnection

2021 ◽  
Author(s):  
Nicole Vilmer ◽  
Sophie Musset
Keyword(s):  
Solar Flares ◽  
Magnetic Energy ◽  
Imaging Spectroscopy ◽  
Active Regions ◽  
Coronal Magnetic Field ◽  
High Energy ◽  
X Rays ◽  
Energetic Electrons ◽  
Radio Imaging ◽  
Gyrosynchrotron Emission

<p>Efficient electron (and ion) acceleration is produced in association with solar flares. Energetic particles play a major role in the active Sun since they contain a large amount of the magnetic energy released during flares. Energetic electrons (and ions) interact with the solar atmosphere and produce high-energy X-rays and γ-rays. Energetic electrons also produce radio emission in a large frequency band through gyrosynchrotron emission processes in the magnetic fields of flaring active regions and conversion of plasma waves when e.g. propagating to the high corona towards the interplanetary medium. It is currently admitted that solar flares are powered by magnetic energy previously stored in the coronal magnetic field and that magnetic energy release is likely to occur on coronal currents sheets along regions of strong gradient of magnetic connectivity. However, understanding the connection between particle acceleration processes and the topology of the complex magnetic structures present in the corona is still a challenging issue. In this talk, we shall review some recent results derived from X-ray and radio imaging spectroscopy of solar flares bringing some new observational constraints on the localization of HXR/radio sources with respect to current sheets, termination shocks in the corona derived from EUV observations.</p>

scholarly journals Edward L. Chupp (1927–2017)

Eos ◽  
2018 ◽  
Vol 99 ◽  
Author(s):  
James Ryan ◽  
Martin Lee
Keyword(s):  
Gamma Rays ◽  
Solar Flares ◽  
Solar Physics ◽  
Cosmic Ray ◽  
High Energy ◽  
First Time

This pioneer in high-energy solar physics devised instruments for observing solar and cosmic ray emissions with which he detected, for the first time, nuclear gamma rays from solar flares.

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.

High energy electrons detected during solar flares

Solar Physics ◽  
1972 ◽  
Vol 23 (2) ◽  
pp. 487-500 ◽  
Author(s):  
C. Dilworth ◽  
D. Maccagni ◽  
F. Perotti ◽  
E. G. Tanzi ◽  
J. P. Mercier ◽  
...  
Keyword(s):  
Solar Flares ◽  
High Energy ◽  
High Energy Electrons

scholarly journals A High Capacity, Room Temperature, Hybrid Flow Battery Consisting of Liquid Na-Cs Anode and Aqueous NaI Catholyte

Batteries ◽  
2018 ◽  
Vol 4 (4) ◽  
pp. 60 ◽  
Author(s):  
Caihong Liu ◽  
Leon Shaw
Keyword(s):  
Room Temperature ◽  
Electrochemical Impedance ◽  
Coulombic Efficiency ◽  
High Capacity ◽  
High Energy ◽  
Flow Battery ◽  
Membrane Interfaces ◽  
Number Of Cycles ◽  
Novel Concept ◽  
First Time

In this study, we have proposed a novel concept of hybrid flow batteries consisting of a molten Na-Cs anode and an aqueous NaI catholyte separated by a NaSICON membrane. A number of carbonaceous electrodes are studied using cyclic voltammetry (CV) for their potentials as the positive electrode of the aqueous NaI catholyte. The charge transfer impedance, interfacial impedance and NaSICON membrane impedance of the Na-Cs ‖ NaI hybrid flow battery are analyzed using electrochemical impedance spectroscopy. The performance of the Na-Cs ‖ NaI hybrid flow battery is evaluated through galvanostatic charge/discharge cycles. This study demonstrates, for the first time, the feasibility of the Na-Cs ‖ NaI hybrid flow battery and shows that the Na-Cs ‖ NaI hybrid flow battery has the potential to achieve the following properties simultaneously: (i) An aqueous NaI catholyte with good cycle stability, (ii) a durable and low impedance NaSICON membrane for a large number of cycles, (iii) stable interfaces at both anode/membrane and cathode/membrane interfaces, (iv) a molten Na-Cs anode capable of repeated Na plating and stripping, and (v) a flow battery with high Coulombic efficiency, high voltaic efficiency, and high energy efficiency.

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