scholarly journals Non-equilibrium ionization by a periodic electron beam

2018 ◽  
Vol 610 ◽  
pp. A67 ◽  
Author(s):  
Elena Dzifčáková ◽  
Jaroslav Dudík
Keyword(s):  
Electron Beam ◽  
Simple Model ◽  
Energy Release ◽  
High Energy ◽  
Time Dependent ◽  
Ionization Equilibrium ◽  
Synthetic Spectra ◽  
High Energy Particles ◽  
Accelerated Particles ◽  
Non Equilibrium

Context. Transition region (TR) spectra typically show the Si IV 1402.8 Å line to be enhanced by a factor of 5 or more compared to the neighboring O IV 1401.2 Å, contrary to predictions of ionization equilibrium models and the Maxwellian distribution of particle energies. Non-equilibrium effects in TR spectra are therefore expected. Aims. To investigate the combination of non-equilibrium ionization and high-energy particles, we apply the model of the periodic electron beam, represented by a κ-distribution that recurs at periods of several seconds, to plasma at chromospheric temperatures of 104 K. This simple model can approximate a burst of energy release involving accelerated particles. Methods. Instantaneous time-dependent charge states of silicon and oxygen were calculated and used to synthesize the instantaneous and period-averaged spectra of Si IV and O IV. Results. The electron beam drives the plasma out of equilibrium. At electron densities of Ne = 1010 cm−3, the plasma is out of ionization equilibrium at all times in all cases we considered, while for a higher density of Ne = 1011 cm−3, ionization equilibrium can be reached toward the end of each period, depending on the conditions. In turn, the character of the period-averaged synthetic spectra also depends on the properties of the beam. While the case of κ = 2 results in spectra with strong or even dominant O IV, higher values of κ can approximate a range of observed TR spectra. Spectra similar to typically observed spectra, with the Si IV 1402.8 Å line about a factor 5 higher than O IV 1401.2 Å, are obtained for κ = 3. An even higher value of κ = 5 results in spectra that are exclusively dominated by Si IV, with negligible O IV emission. This is a possible interpretation of the TR spectra of UV (Ellerman) bursts, although an interpretation that requires a density that is 1–3 orders of magnitude lower than for equilibrium estimates.

scholarly journals Particle Acceleration in Solar Flares and Coronal Mass Ejections

2000 ◽  
Vol 195 ◽  
pp. 15-25
Author(s):  
R. P. Lin
Keyword(s):  
Particle Acceleration ◽  
Energy Release ◽  
Coronal Mass Ejections ◽  
Solar Flares ◽  
Gamma Ray ◽  
Solar Energetic Particle ◽  
High Energy ◽  
Total Rate ◽  
Solar Energetic Particle Events ◽  
High Energy Particles

The Sun accelerates ions up to tens of GeV and electrons up to 100s of MeV in solar flares and coronal mass ejections. The energy in the accelerated tens-of-keV electrons and possibly ~1 MeV ions constitutes a significant fraction of the total energy released in a flare, implying that the particle acceleration and flare energy release mechanisms are intimately related. The total rate of energy release in transients from flares down to microflares/nanoflares may be significant for heating the active solar corona.Shock waves driven by fast CMEs appear to accelerate the high-energy particles in large solar energetic particle events detected at 1 AU. Smaller SEP events are dominated by ~1 to tens-of-keV electrons, with low fluxes of up to a few MeV/nucleon ions, typically enriched in 3He. The acceleration in gamma-ray flares appears to resemble that in these small electron-3He SEP events.

scholarly journals Particle acceleration at colliding shock waves

2020 ◽  
Vol 494 (3) ◽  
pp. 3166-3176 ◽  
Author(s):  
T Vieu ◽  
S Gabici ◽  
V Tatischeff
Keyword(s):  
Shock Waves ◽  
High Energy ◽  
Time Dependent ◽  
Shock Acceleration ◽  
Diffusive Shock Acceleration ◽  
Mathematical Methods ◽  
Accretion Flows ◽  
Self Similar Solution ◽  
Self Similar ◽  
Accelerated Particles

ABSTRACT We model the diffusive shock acceleration of particles in a system of two colliding shock waves and present a method to solve the time-dependent problem analytically in the test-particle approximation and high energy limit. In particular, we show that in this limit the problem can be analysed with the help of a self-similar solution. While a number of recent works predict hard (E−1) spectra for the accelerated particles in the stationary limit, or the appearance of spectral breaks, we found instead that the spectrum of accelerated particles in a time-dependent collision follows quite closely the canonical E−2 prediction of diffusive shock acceleration at a single shock, except at the highest energy, where a hardening appears, originating a bumpy feature just before the exponential cut-off. We also investigated the effect of the reacceleration of pre-existing cosmic rays by a system of two shocks, and found that under certain conditions spectral features can appear in the cut-off region. Finally, the mathematical methods presented here are very general and could be easily applied to a variety of astrophysical situations, including for instance standing shocks in accretion flows, diverging shocks, backward collisions of a slow shock by a faster shock, and wind–wind or shock–wind collisions.

scholarly journals Study on the escape timescale of high-energy particles from supernova remnants through thermal X-ray properties

2020 ◽  
Vol 72 (5) ◽  
Author(s):  
Hiromasa Suzuki ◽  
Aya Bamba ◽  
Ryo Yamazaki ◽  
Yutaka Ohira
Keyword(s):  
Power Law ◽  
Supernova Remnants ◽  
Gamma Ray ◽  
Cosmic Ray ◽  
High Energy ◽  
Spectral Shape ◽  
X Ray ◽  
Galactic Cosmic Ray ◽  
High Energy Particles ◽  
Accelerated Particles

Abstract In the current decade, GeV/TeV gamma-ray observations of several supernova remnants (SNRs) have implied that accelerated particles are escaping from their acceleration sites. However, when and how they escape from the SNR vicinities are yet to be understood. Recent studies have suggested that the particle escape might develop with thermal plasma ages of the SNRs. We present a systematic study on the time evolution of particle escape using thermal X-ray properties and gamma-ray spectra using 38 SNRs associated with GeV/TeV gamma-ray emissions. We conducted spectral fittings on the gamma-ray spectra using exponential cutoff power-law and broken power-law models to estimate the exponential cutoff or the break energies, both of which are indicators of particle escape. Plots of the gamma-ray cutoff/break energies over the plasma ages show similar tendencies to those predicted by analytical/numerical calculations of particle escape under conditions in which a shock is interacting with thin interstellar medium or clouds. The particle escape timescale is estimated as ∼100 kyr from the decreasing trends of the total energy of the confined protons with the plasma age. The large dispersions of the cutoff/break energies in the data may suggest an intrinsic variety of particle escape environments. This might be the cause of the complicated Galactic cosmic ray spectral shape measured on Earth.

scholarly journals The nature of seismic sources associated with a proton-reach solar flare

2007 ◽  
Vol 3 (S247) ◽  
pp. 59-65 ◽  
Author(s):  
Valentyna V. Zharkova ◽  
Serhij I. Zharkov
Keyword(s):  
Electron Beam ◽  
Solar Flare ◽  
Seismic Wave ◽  
Lower Energy ◽  
Seismic Waves ◽  
Power Laws ◽  
High Energy ◽  
Seismic Sources ◽  
Γ Rays ◽  
High Energy Particles

AbstractThe momenta and start times measured from the TD diagrams in 3 seismic sources observed in the flare of 28 October 2003 are compared with those delivered to the photosphere by different kinds of high energy particles as well as by the hydrodynamic shocks caused by these particles. The energetic protons with energy power laws combined with quasi-thermal ones are shown to form hydrodynamic shocks deeply in a flaring atmosphere which deliver the required momentum to the photosphere within a measured timescale. The seismic waves observed in two sources associated with γ-rays can be explained by the momenta produced by hydrodynamic shocks caused by mixed proton beams and jets. The seismic wave in the source asociated with HXR only and delayed by 4 and 2 minutes from the first and second HXR bursts is likely to be associated with a hydrodynamic shock occurring from precipitation of a very powerful and hard electron beam possibly mixed with quasi-thermal lower energy protons.

scholarly journals Emission of high energy particles in heavy ion collisions and a non-equilibrium equation of state

2019 ◽  
Vol 204 ◽  
pp. 03018
Author(s):  
Alexander T. D’yachenko ◽  
Ivan A. Mitropolsky
Keyword(s):  
Equation Of State ◽  
Cross Sections ◽  
Equilibrium Equation ◽  
Heavy Ion ◽  
High Energy ◽  
Intermediate Energies ◽  
Ion Collisions ◽  
Hydrodynamic Approach ◽  
High Energy Particles ◽  
Non Equilibrium

A hydrodynamic approach with a non-equilibrium equation of state is used to describe the collisions of heavy ions at medium and intermediate energies. In the development of this approach, with the inclusion of nuclear viscosity effects and the introduction of an amendment to the microcanonical distribution, the double differential cross sections of proton emission in collisions of different nuclei are calculated, which are in agreement with the available experimental data on the emission of high-energy particles, including the cumulative spectral region.

Effects of High-Energy Ions on Synthetic Quartz

1972 ◽  
Vol 30 ◽  
pp. 544-545
Author(s):  
Joseph J. Comer ◽  
Charles Bergeron ◽  
Lester F. Lowe
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Beam ◽  
High Energy ◽  
Transmission Electron ◽  
Kikuchi Lines ◽  
High Energy Ions ◽  
Diffraction Patterns ◽  
Dauphiné Twinning ◽  
Beam Damage

Using a Van De Graaff Accelerator thinned specimens were subjected to bombardment by 3 MeV N+ ions to fluences ranging from 4x1013 to 2x1016 ions/cm2. They were then examined by transmission electron microscopy and reflection electron diffraction using a 100 KV electron beam.At the lowest fluence of 4x1013 ions/cm2 diffraction patterns of the specimens contained Kikuchi lines which appeared somewhat broader and more diffuse than those obtained on unirradiated material. No damage could be detected by transmission electron microscopy in unannealed specimens. However, Dauphiné twinning was particularly pronounced after heating to 665°C for one hour and cooling to room temperature. The twins, seen in Fig. 1, were often less than .25 μm in size, smaller than those formed in unirradiated material and present in greater number. The results are in agreement with earlier observations on the effect of electron beam damage on Dauphiné twinning.

Electron beam induced effects in Cu/GeSe2amorphous films

2003 ◽  
Vol 777 ◽  
Author(s):  
J.S. Romero ◽  
A.G. Fitzgerald
Keyword(s):  
Thin Films ◽  
Electron Beam ◽  
Simple Model ◽  
Copper Concentration ◽  
Negative Charge ◽  
Electron Bombardment ◽  
Continuous Operation ◽  
Electron Radiation ◽  
Crystalline Product ◽  
Intense Electron

AbstractCopper migration is observed in the SEM in amorphous GeSe2/Cu thin films when an electron beam is focused in pulsed or continuous operation on the surface of these thin films. The phenomenon can be explained using a simple model in which the population of D- centers is considered to increase upon electron irradiation. The increase in the D- center population is envisaged as due to the breaking of bonds by the electron radiation and by the constant presence of negative charge in irradiated regions. Changes in copper concentration of 20%-30% have been obtained. Additionally we have observed the local crystallization of amorphous GeSe2/Cu thin films in the TEM when the samples were subjected to intense electron bombardment. The crystalline product has been identified as Berzelianite (Cu2Se).

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